firewire: ohci: remove unused dualbuffer IR code

[net-next-2.6.git] / drivers / firewire / ohci.c

/*
 * Driver for OHCI 1394 controllers
 *
 * Copyright (C) 2003-2006 Kristian Hoegsberg <krh@bitplanet.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#include <linux/compiler.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/dma-mapping.h>
#include <linux/firewire.h>
#include <linux/firewire-constants.h>
#include <linux/gfp.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/pci.h>
#include <linux/pci_ids.h>
#include <linux/spinlock.h>
#include <linux/string.h>

#include <asm/byteorder.h>
#include <asm/page.h>
#include <asm/system.h>

#ifdef CONFIG_PPC_PMAC
#include <asm/pmac_feature.h>
#endif

#include "core.h"
#include "ohci.h"

#define DESCRIPTOR_OUTPUT_MORE		0
#define DESCRIPTOR_OUTPUT_LAST		(1 << 12)
#define DESCRIPTOR_INPUT_MORE		(2 << 12)
#define DESCRIPTOR_INPUT_LAST		(3 << 12)
#define DESCRIPTOR_STATUS		(1 << 11)
#define DESCRIPTOR_KEY_IMMEDIATE	(2 << 8)
#define DESCRIPTOR_PING			(1 << 7)
#define DESCRIPTOR_YY			(1 << 6)
#define DESCRIPTOR_NO_IRQ		(0 << 4)
#define DESCRIPTOR_IRQ_ERROR		(1 << 4)
#define DESCRIPTOR_IRQ_ALWAYS		(3 << 4)
#define DESCRIPTOR_BRANCH_ALWAYS	(3 << 2)
#define DESCRIPTOR_WAIT			(3 << 0)

struct descriptor {
	__le16 req_count;
	__le16 control;
	__le32 data_address;
	__le32 branch_address;
	__le16 res_count;
	__le16 transfer_status;
} __attribute__((aligned(16)));

#define CONTROL_SET(regs)	(regs)
#define CONTROL_CLEAR(regs)	((regs) + 4)
#define COMMAND_PTR(regs)	((regs) + 12)
#define CONTEXT_MATCH(regs)	((regs) + 16)

struct ar_buffer {
	struct descriptor descriptor;
	struct ar_buffer *next;
	__le32 data[0];
};

struct ar_context {
	struct fw_ohci *ohci;
	struct ar_buffer *current_buffer;
	struct ar_buffer *last_buffer;
	void *pointer;
	u32 regs;
	struct tasklet_struct tasklet;
};

struct context;

typedef int (*descriptor_callback_t)(struct context *ctx,
				     struct descriptor *d,
				     struct descriptor *last);

/*
 * A buffer that contains a block of DMA-able coherent memory used for
 * storing a portion of a DMA descriptor program.
 */
struct descriptor_buffer {
	struct list_head list;
	dma_addr_t buffer_bus;
	size_t buffer_size;
	size_t used;
	struct descriptor buffer[0];
};

struct context {
	struct fw_ohci *ohci;
	u32 regs;
	int total_allocation;

	/*
	 * List of page-sized buffers for storing DMA descriptors.
	 * Head of list contains buffers in use and tail of list contains
	 * free buffers.
	 */
	struct list_head buffer_list;

	/*
	 * Pointer to a buffer inside buffer_list that contains the tail
	 * end of the current DMA program.
	 */
	struct descriptor_buffer *buffer_tail;

	/*
	 * The descriptor containing the branch address of the first
	 * descriptor that has not yet been filled by the device.
	 */
	struct descriptor *last;

	/*
	 * The last descriptor in the DMA program.  It contains the branch
	 * address that must be updated upon appending a new descriptor.
	 */
	struct descriptor *prev;

	descriptor_callback_t callback;

	struct tasklet_struct tasklet;
};

#define IT_HEADER_SY(v)          ((v) <<  0)
#define IT_HEADER_TCODE(v)       ((v) <<  4)
#define IT_HEADER_CHANNEL(v)     ((v) <<  8)
#define IT_HEADER_TAG(v)         ((v) << 14)
#define IT_HEADER_SPEED(v)       ((v) << 16)
#define IT_HEADER_DATA_LENGTH(v) ((v) << 16)

struct iso_context {
	struct fw_iso_context base;
	struct context context;
	int excess_bytes;
	void *header;
	size_t header_length;
};

#define CONFIG_ROM_SIZE 1024

struct fw_ohci {
	struct fw_card card;

	__iomem char *registers;
	dma_addr_t self_id_bus;
	__le32 *self_id_cpu;
	struct tasklet_struct bus_reset_tasklet;
	int node_id;
	int generation;
	int request_generation;	/* for timestamping incoming requests */

	bool old_uninorth;
	bool bus_reset_packet_quirk;
	bool iso_cycle_timer_quirk;

	/*
	 * Spinlock for accessing fw_ohci data.  Never call out of
	 * this driver with this lock held.
	 */
	spinlock_t lock;
	u32 self_id_buffer[512];

	/* Config rom buffers */
	__be32 *config_rom;
	dma_addr_t config_rom_bus;
	__be32 *next_config_rom;
	dma_addr_t next_config_rom_bus;
	__be32 next_header;

	struct ar_context ar_request_ctx;
	struct ar_context ar_response_ctx;
	struct context at_request_ctx;
	struct context at_response_ctx;

	u32 it_context_mask;
	struct iso_context *it_context_list;
	u64 ir_context_channels;
	u32 ir_context_mask;
	struct iso_context *ir_context_list;
};

static inline struct fw_ohci *fw_ohci(struct fw_card *card)
{
	return container_of(card, struct fw_ohci, card);
}

#define IT_CONTEXT_CYCLE_MATCH_ENABLE	0x80000000
#define IR_CONTEXT_BUFFER_FILL		0x80000000
#define IR_CONTEXT_ISOCH_HEADER		0x40000000
#define IR_CONTEXT_CYCLE_MATCH_ENABLE	0x20000000
#define IR_CONTEXT_MULTI_CHANNEL_MODE	0x10000000
#define IR_CONTEXT_DUAL_BUFFER_MODE	0x08000000

#define CONTEXT_RUN	0x8000
#define CONTEXT_WAKE	0x1000
#define CONTEXT_DEAD	0x0800
#define CONTEXT_ACTIVE	0x0400

#define OHCI1394_MAX_AT_REQ_RETRIES	0xf
#define OHCI1394_MAX_AT_RESP_RETRIES	0x2
#define OHCI1394_MAX_PHYS_RESP_RETRIES	0x8

#define OHCI1394_REGISTER_SIZE		0x800
#define OHCI_LOOP_COUNT			500
#define OHCI1394_PCI_HCI_Control	0x40
#define SELF_ID_BUF_SIZE		0x800
#define OHCI_TCODE_PHY_PACKET		0x0e
#define OHCI_VERSION_1_1		0x010010

static char ohci_driver_name[] = KBUILD_MODNAME;

#ifdef CONFIG_FIREWIRE_OHCI_DEBUG

#define OHCI_PARAM_DEBUG_AT_AR		1
#define OHCI_PARAM_DEBUG_SELFIDS	2
#define OHCI_PARAM_DEBUG_IRQS		4
#define OHCI_PARAM_DEBUG_BUSRESETS	8 /* only effective before chip init */

static int param_debug;
module_param_named(debug, param_debug, int, 0644);
MODULE_PARM_DESC(debug, "Verbose logging (default = 0"
	", AT/AR events = "	__stringify(OHCI_PARAM_DEBUG_AT_AR)
	", self-IDs = "		__stringify(OHCI_PARAM_DEBUG_SELFIDS)
	", IRQs = "		__stringify(OHCI_PARAM_DEBUG_IRQS)
	", busReset events = "	__stringify(OHCI_PARAM_DEBUG_BUSRESETS)
	", or a combination, or all = -1)");

static void log_irqs(u32 evt)
{
	if (likely(!(param_debug &
			(OHCI_PARAM_DEBUG_IRQS | OHCI_PARAM_DEBUG_BUSRESETS))))
		return;

	if (!(param_debug & OHCI_PARAM_DEBUG_IRQS) &&
	    !(evt & OHCI1394_busReset))
		return;

	fw_notify("IRQ %08x%s%s%s%s%s%s%s%s%s%s%s%s%s\n", evt,
	    evt & OHCI1394_selfIDComplete	? " selfID"		: "",
	    evt & OHCI1394_RQPkt		? " AR_req"		: "",
	    evt & OHCI1394_RSPkt		? " AR_resp"		: "",
	    evt & OHCI1394_reqTxComplete	? " AT_req"		: "",
	    evt & OHCI1394_respTxComplete	? " AT_resp"		: "",
	    evt & OHCI1394_isochRx		? " IR"			: "",
	    evt & OHCI1394_isochTx		? " IT"			: "",
	    evt & OHCI1394_postedWriteErr	? " postedWriteErr"	: "",
	    evt & OHCI1394_cycleTooLong		? " cycleTooLong"	: "",
	    evt & OHCI1394_cycleInconsistent	? " cycleInconsistent"	: "",
	    evt & OHCI1394_regAccessFail	? " regAccessFail"	: "",
	    evt & OHCI1394_busReset		? " busReset"		: "",
	    evt & ~(OHCI1394_selfIDComplete | OHCI1394_RQPkt |
		    OHCI1394_RSPkt | OHCI1394_reqTxComplete |
		    OHCI1394_respTxComplete | OHCI1394_isochRx |
		    OHCI1394_isochTx | OHCI1394_postedWriteErr |
		    OHCI1394_cycleTooLong | OHCI1394_cycleInconsistent |
		    OHCI1394_regAccessFail | OHCI1394_busReset)
						? " ?"			: "");
}

static const char *speed[] = {
	[0] = "S100", [1] = "S200", [2] = "S400",    [3] = "beta",
};
static const char *power[] = {
	[0] = "+0W",  [1] = "+15W", [2] = "+30W",    [3] = "+45W",
	[4] = "-3W",  [5] = " ?W",  [6] = "-3..-6W", [7] = "-3..-10W",
};
static const char port[] = { '.', '-', 'p', 'c', };

static char _p(u32 *s, int shift)
{
	return port[*s >> shift & 3];
}

static void log_selfids(int node_id, int generation, int self_id_count, u32 *s)
{
	if (likely(!(param_debug & OHCI_PARAM_DEBUG_SELFIDS)))
		return;

	fw_notify("%d selfIDs, generation %d, local node ID %04x\n",
		  self_id_count, generation, node_id);

	for (; self_id_count--; ++s)
		if ((*s & 1 << 23) == 0)
			fw_notify("selfID 0: %08x, phy %d [%c%c%c] "
			    "%s gc=%d %s %s%s%s\n",
			    *s, *s >> 24 & 63, _p(s, 6), _p(s, 4), _p(s, 2),
			    speed[*s >> 14 & 3], *s >> 16 & 63,
			    power[*s >> 8 & 7], *s >> 22 & 1 ? "L" : "",
			    *s >> 11 & 1 ? "c" : "", *s & 2 ? "i" : "");
		else
			fw_notify("selfID n: %08x, phy %d [%c%c%c%c%c%c%c%c]\n",
			    *s, *s >> 24 & 63,
			    _p(s, 16), _p(s, 14), _p(s, 12), _p(s, 10),
			    _p(s,  8), _p(s,  6), _p(s,  4), _p(s,  2));
}

static const char *evts[] = {
	[0x00] = "evt_no_status",	[0x01] = "-reserved-",
	[0x02] = "evt_long_packet",	[0x03] = "evt_missing_ack",
	[0x04] = "evt_underrun",	[0x05] = "evt_overrun",
	[0x06] = "evt_descriptor_read",	[0x07] = "evt_data_read",
	[0x08] = "evt_data_write",	[0x09] = "evt_bus_reset",
	[0x0a] = "evt_timeout",		[0x0b] = "evt_tcode_err",
	[0x0c] = "-reserved-",		[0x0d] = "-reserved-",
	[0x0e] = "evt_unknown",		[0x0f] = "evt_flushed",
	[0x10] = "-reserved-",		[0x11] = "ack_complete",
	[0x12] = "ack_pending ",	[0x13] = "-reserved-",
	[0x14] = "ack_busy_X",		[0x15] = "ack_busy_A",
	[0x16] = "ack_busy_B",		[0x17] = "-reserved-",
	[0x18] = "-reserved-",		[0x19] = "-reserved-",
	[0x1a] = "-reserved-",		[0x1b] = "ack_tardy",
	[0x1c] = "-reserved-",		[0x1d] = "ack_data_error",
	[0x1e] = "ack_type_error",	[0x1f] = "-reserved-",
	[0x20] = "pending/cancelled",
};
static const char *tcodes[] = {
	[0x0] = "QW req",		[0x1] = "BW req",
	[0x2] = "W resp",		[0x3] = "-reserved-",
	[0x4] = "QR req",		[0x5] = "BR req",
	[0x6] = "QR resp",		[0x7] = "BR resp",
	[0x8] = "cycle start",		[0x9] = "Lk req",
	[0xa] = "async stream packet",	[0xb] = "Lk resp",
	[0xc] = "-reserved-",		[0xd] = "-reserved-",
	[0xe] = "link internal",	[0xf] = "-reserved-",
};
static const char *phys[] = {
	[0x0] = "phy config packet",	[0x1] = "link-on packet",
	[0x2] = "self-id packet",	[0x3] = "-reserved-",
};

static void log_ar_at_event(char dir, int speed, u32 *header, int evt)
{
	int tcode = header[0] >> 4 & 0xf;
	char specific[12];

	if (likely(!(param_debug & OHCI_PARAM_DEBUG_AT_AR)))
		return;

	if (unlikely(evt >= ARRAY_SIZE(evts)))
			evt = 0x1f;

	if (evt == OHCI1394_evt_bus_reset) {
		fw_notify("A%c evt_bus_reset, generation %d\n",
		    dir, (header[2] >> 16) & 0xff);
		return;
	}

	if (header[0] == ~header[1]) {
		fw_notify("A%c %s, %s, %08x\n",
		    dir, evts[evt], phys[header[0] >> 30 & 0x3], header[0]);
		return;
	}

	switch (tcode) {
	case 0x0: case 0x6: case 0x8:
		snprintf(specific, sizeof(specific), " = %08x",
			 be32_to_cpu((__force __be32)header[3]));
		break;
	case 0x1: case 0x5: case 0x7: case 0x9: case 0xb:
		snprintf(specific, sizeof(specific), " %x,%x",
			 header[3] >> 16, header[3] & 0xffff);
		break;
	default:
		specific[0] = '\0';
	}

	switch (tcode) {
	case 0xe: case 0xa:
		fw_notify("A%c %s, %s\n", dir, evts[evt], tcodes[tcode]);
		break;
	case 0x0: case 0x1: case 0x4: case 0x5: case 0x9:
		fw_notify("A%c spd %x tl %02x, "
		    "%04x -> %04x, %s, "
		    "%s, %04x%08x%s\n",
		    dir, speed, header[0] >> 10 & 0x3f,
		    header[1] >> 16, header[0] >> 16, evts[evt],
		    tcodes[tcode], header[1] & 0xffff, header[2], specific);
		break;
	default:
		fw_notify("A%c spd %x tl %02x, "
		    "%04x -> %04x, %s, "
		    "%s%s\n",
		    dir, speed, header[0] >> 10 & 0x3f,
		    header[1] >> 16, header[0] >> 16, evts[evt],
		    tcodes[tcode], specific);
	}
}

#else

#define log_irqs(evt)
#define log_selfids(node_id, generation, self_id_count, sid)
#define log_ar_at_event(dir, speed, header, evt)

#endif /* CONFIG_FIREWIRE_OHCI_DEBUG */

static inline void reg_write(const struct fw_ohci *ohci, int offset, u32 data)
{
	writel(data, ohci->registers + offset);
}

static inline u32 reg_read(const struct fw_ohci *ohci, int offset)
{
	return readl(ohci->registers + offset);
}

static inline void flush_writes(const struct fw_ohci *ohci)
{
	/* Do a dummy read to flush writes. */
	reg_read(ohci, OHCI1394_Version);
}

static int ohci_update_phy_reg(struct fw_card *card, int addr,
			       int clear_bits, int set_bits)
{
	struct fw_ohci *ohci = fw_ohci(card);
	u32 val, old;

	reg_write(ohci, OHCI1394_PhyControl, OHCI1394_PhyControl_Read(addr));
	flush_writes(ohci);
	msleep(2);
	val = reg_read(ohci, OHCI1394_PhyControl);
	if ((val & OHCI1394_PhyControl_ReadDone) == 0) {
		fw_error("failed to set phy reg bits.\n");
		return -EBUSY;
	}

	old = OHCI1394_PhyControl_ReadData(val);
	old = (old & ~clear_bits) | set_bits;
	reg_write(ohci, OHCI1394_PhyControl,
		  OHCI1394_PhyControl_Write(addr, old));

	return 0;
}

static int ar_context_add_page(struct ar_context *ctx)
{
	struct device *dev = ctx->ohci->card.device;
	struct ar_buffer *ab;
	dma_addr_t uninitialized_var(ab_bus);
	size_t offset;

	ab = dma_alloc_coherent(dev, PAGE_SIZE, &ab_bus, GFP_ATOMIC);
	if (ab == NULL)
		return -ENOMEM;

	ab->next = NULL;
	memset(&ab->descriptor, 0, sizeof(ab->descriptor));
	ab->descriptor.control        = cpu_to_le16(DESCRIPTOR_INPUT_MORE |
						    DESCRIPTOR_STATUS |
						    DESCRIPTOR_BRANCH_ALWAYS);
	offset = offsetof(struct ar_buffer, data);
	ab->descriptor.req_count      = cpu_to_le16(PAGE_SIZE - offset);
	ab->descriptor.data_address   = cpu_to_le32(ab_bus + offset);
	ab->descriptor.res_count      = cpu_to_le16(PAGE_SIZE - offset);
	ab->descriptor.branch_address = 0;

	ctx->last_buffer->descriptor.branch_address = cpu_to_le32(ab_bus | 1);
	ctx->last_buffer->next = ab;
	ctx->last_buffer = ab;

	reg_write(ctx->ohci, CONTROL_SET(ctx->regs), CONTEXT_WAKE);
	flush_writes(ctx->ohci);

	return 0;
}

static void ar_context_release(struct ar_context *ctx)
{
	struct ar_buffer *ab, *ab_next;
	size_t offset;
	dma_addr_t ab_bus;

	for (ab = ctx->current_buffer; ab; ab = ab_next) {
		ab_next = ab->next;
		offset = offsetof(struct ar_buffer, data);
		ab_bus = le32_to_cpu(ab->descriptor.data_address) - offset;
		dma_free_coherent(ctx->ohci->card.device, PAGE_SIZE,
				  ab, ab_bus);
	}
}

#if defined(CONFIG_PPC_PMAC) && defined(CONFIG_PPC32)
#define cond_le32_to_cpu(v) \
	(ohci->old_uninorth ? (__force __u32)(v) : le32_to_cpu(v))
#else
#define cond_le32_to_cpu(v) le32_to_cpu(v)
#endif

static __le32 *handle_ar_packet(struct ar_context *ctx, __le32 *buffer)
{
	struct fw_ohci *ohci = ctx->ohci;
	struct fw_packet p;
	u32 status, length, tcode;
	int evt;

	p.header[0] = cond_le32_to_cpu(buffer[0]);
	p.header[1] = cond_le32_to_cpu(buffer[1]);
	p.header[2] = cond_le32_to_cpu(buffer[2]);

	tcode = (p.header[0] >> 4) & 0x0f;
	switch (tcode) {
	case TCODE_WRITE_QUADLET_REQUEST:
	case TCODE_READ_QUADLET_RESPONSE:
		p.header[3] = (__force __u32) buffer[3];
		p.header_length = 16;
		p.payload_length = 0;
		break;

	case TCODE_READ_BLOCK_REQUEST :
		p.header[3] = cond_le32_to_cpu(buffer[3]);
		p.header_length = 16;
		p.payload_length = 0;
		break;

	case TCODE_WRITE_BLOCK_REQUEST:
	case TCODE_READ_BLOCK_RESPONSE:
	case TCODE_LOCK_REQUEST:
	case TCODE_LOCK_RESPONSE:
		p.header[3] = cond_le32_to_cpu(buffer[3]);
		p.header_length = 16;
		p.payload_length = p.header[3] >> 16;
		break;

	case TCODE_WRITE_RESPONSE:
	case TCODE_READ_QUADLET_REQUEST:
	case OHCI_TCODE_PHY_PACKET:
		p.header_length = 12;
		p.payload_length = 0;
		break;

	default:
		/* FIXME: Stop context, discard everything, and restart? */
		p.header_length = 0;
		p.payload_length = 0;
	}

	p.payload = (void *) buffer + p.header_length;

	/* FIXME: What to do about evt_* errors? */
	length = (p.header_length + p.payload_length + 3) / 4;
	status = cond_le32_to_cpu(buffer[length]);
	evt    = (status >> 16) & 0x1f;

	p.ack        = evt - 16;
	p.speed      = (status >> 21) & 0x7;
	p.timestamp  = status & 0xffff;
	p.generation = ohci->request_generation;

	log_ar_at_event('R', p.speed, p.header, evt);

	/*
	 * The OHCI bus reset handler synthesizes a phy packet with
	 * the new generation number when a bus reset happens (see
	 * section 8.4.2.3).  This helps us determine when a request
	 * was received and make sure we send the response in the same
	 * generation.  We only need this for requests; for responses
	 * we use the unique tlabel for finding the matching
	 * request.
	 *
	 * Alas some chips sometimes emit bus reset packets with a
	 * wrong generation.  We set the correct generation for these
	 * at a slightly incorrect time (in bus_reset_tasklet).
	 */
	if (evt == OHCI1394_evt_bus_reset) {
		if (!ohci->bus_reset_packet_quirk)
			ohci->request_generation = (p.header[2] >> 16) & 0xff;
	} else if (ctx == &ohci->ar_request_ctx) {
		fw_core_handle_request(&ohci->card, &p);
	} else {
		fw_core_handle_response(&ohci->card, &p);
	}

	return buffer + length + 1;
}

static void ar_context_tasklet(unsigned long data)
{
	struct ar_context *ctx = (struct ar_context *)data;
	struct fw_ohci *ohci = ctx->ohci;
	struct ar_buffer *ab;
	struct descriptor *d;
	void *buffer, *end;

	ab = ctx->current_buffer;
	d = &ab->descriptor;

	if (d->res_count == 0) {
		size_t size, rest, offset;
		dma_addr_t start_bus;
		void *start;

		/*
		 * This descriptor is finished and we may have a
		 * packet split across this and the next buffer. We
		 * reuse the page for reassembling the split packet.
		 */

		offset = offsetof(struct ar_buffer, data);
		start = buffer = ab;
		start_bus = le32_to_cpu(ab->descriptor.data_address) - offset;

		ab = ab->next;
		d = &ab->descriptor;
		size = buffer + PAGE_SIZE - ctx->pointer;
		rest = le16_to_cpu(d->req_count) - le16_to_cpu(d->res_count);
		memmove(buffer, ctx->pointer, size);
		memcpy(buffer + size, ab->data, rest);
		ctx->current_buffer = ab;
		ctx->pointer = (void *) ab->data + rest;
		end = buffer + size + rest;

		while (buffer < end)
			buffer = handle_ar_packet(ctx, buffer);

		dma_free_coherent(ohci->card.device, PAGE_SIZE,
				  start, start_bus);
		ar_context_add_page(ctx);
	} else {
		buffer = ctx->pointer;
		ctx->pointer = end =
			(void *) ab + PAGE_SIZE - le16_to_cpu(d->res_count);

		while (buffer < end)
			buffer = handle_ar_packet(ctx, buffer);
	}
}

static int ar_context_init(struct ar_context *ctx,
			   struct fw_ohci *ohci, u32 regs)
{
	struct ar_buffer ab;

	ctx->regs        = regs;
	ctx->ohci        = ohci;
	ctx->last_buffer = &ab;
	tasklet_init(&ctx->tasklet, ar_context_tasklet, (unsigned long)ctx);

	ar_context_add_page(ctx);
	ar_context_add_page(ctx);
	ctx->current_buffer = ab.next;
	ctx->pointer = ctx->current_buffer->data;

	return 0;
}

static void ar_context_run(struct ar_context *ctx)
{
	struct ar_buffer *ab = ctx->current_buffer;
	dma_addr_t ab_bus;
	size_t offset;

	offset = offsetof(struct ar_buffer, data);
	ab_bus = le32_to_cpu(ab->descriptor.data_address) - offset;

	reg_write(ctx->ohci, COMMAND_PTR(ctx->regs), ab_bus | 1);
	reg_write(ctx->ohci, CONTROL_SET(ctx->regs), CONTEXT_RUN);
	flush_writes(ctx->ohci);
}

static struct descriptor *find_branch_descriptor(struct descriptor *d, int z)
{
	int b, key;

	b   = (le16_to_cpu(d->control) & DESCRIPTOR_BRANCH_ALWAYS) >> 2;
	key = (le16_to_cpu(d->control) & DESCRIPTOR_KEY_IMMEDIATE) >> 8;

	/* figure out which descriptor the branch address goes in */
	if (z == 2 && (b == 3 || key == 2))
		return d;
	else
		return d + z - 1;
}

static void context_tasklet(unsigned long data)
{
	struct context *ctx = (struct context *) data;
	struct descriptor *d, *last;
	u32 address;
	int z;
	struct descriptor_buffer *desc;

	desc = list_entry(ctx->buffer_list.next,
			struct descriptor_buffer, list);
	last = ctx->last;
	while (last->branch_address != 0) {
		struct descriptor_buffer *old_desc = desc;
		address = le32_to_cpu(last->branch_address);
		z = address & 0xf;
		address &= ~0xf;

		/* If the branch address points to a buffer outside of the
		 * current buffer, advance to the next buffer. */
		if (address < desc->buffer_bus ||
				address >= desc->buffer_bus + desc->used)
			desc = list_entry(desc->list.next,
					struct descriptor_buffer, list);
		d = desc->buffer + (address - desc->buffer_bus) / sizeof(*d);
		last = find_branch_descriptor(d, z);

		if (!ctx->callback(ctx, d, last))
			break;

		if (old_desc != desc) {
			/* If we've advanced to the next buffer, move the
			 * previous buffer to the free list. */
			unsigned long flags;
			old_desc->used = 0;
			spin_lock_irqsave(&ctx->ohci->lock, flags);
			list_move_tail(&old_desc->list, &ctx->buffer_list);
			spin_unlock_irqrestore(&ctx->ohci->lock, flags);
		}
		ctx->last = last;
	}
}

/*
 * Allocate a new buffer and add it to the list of free buffers for this
 * context.  Must be called with ohci->lock held.
 */
static int context_add_buffer(struct context *ctx)
{
	struct descriptor_buffer *desc;
	dma_addr_t uninitialized_var(bus_addr);
	int offset;

	/*
	 * 16MB of descriptors should be far more than enough for any DMA
	 * program.  This will catch run-away userspace or DoS attacks.
	 */
	if (ctx->total_allocation >= 16*1024*1024)
		return -ENOMEM;

	desc = dma_alloc_coherent(ctx->ohci->card.device, PAGE_SIZE,
			&bus_addr, GFP_ATOMIC);
	if (!desc)
		return -ENOMEM;

	offset = (void *)&desc->buffer - (void *)desc;
	desc->buffer_size = PAGE_SIZE - offset;
	desc->buffer_bus = bus_addr + offset;
	desc->used = 0;

	list_add_tail(&desc->list, &ctx->buffer_list);
	ctx->total_allocation += PAGE_SIZE;

	return 0;
}

static int context_init(struct context *ctx, struct fw_ohci *ohci,
			u32 regs, descriptor_callback_t callback)
{
	ctx->ohci = ohci;
	ctx->regs = regs;
	ctx->total_allocation = 0;

	INIT_LIST_HEAD(&ctx->buffer_list);
	if (context_add_buffer(ctx) < 0)
		return -ENOMEM;

	ctx->buffer_tail = list_entry(ctx->buffer_list.next,
			struct descriptor_buffer, list);

	tasklet_init(&ctx->tasklet, context_tasklet, (unsigned long)ctx);
	ctx->callback = callback;

	/*
	 * We put a dummy descriptor in the buffer that has a NULL
	 * branch address and looks like it's been sent.  That way we
	 * have a descriptor to append DMA programs to.
	 */
	memset(ctx->buffer_tail->buffer, 0, sizeof(*ctx->buffer_tail->buffer));
	ctx->buffer_tail->buffer->control = cpu_to_le16(DESCRIPTOR_OUTPUT_LAST);
	ctx->buffer_tail->buffer->transfer_status = cpu_to_le16(0x8011);
	ctx->buffer_tail->used += sizeof(*ctx->buffer_tail->buffer);
	ctx->last = ctx->buffer_tail->buffer;
	ctx->prev = ctx->buffer_tail->buffer;

	return 0;
}

static void context_release(struct context *ctx)
{
	struct fw_card *card = &ctx->ohci->card;
	struct descriptor_buffer *desc, *tmp;

	list_for_each_entry_safe(desc, tmp, &ctx->buffer_list, list)
		dma_free_coherent(card->device, PAGE_SIZE, desc,
			desc->buffer_bus -
			((void *)&desc->buffer - (void *)desc));
}

/* Must be called with ohci->lock held */
static struct descriptor *context_get_descriptors(struct context *ctx,
						  int z, dma_addr_t *d_bus)
{
	struct descriptor *d = NULL;
	struct descriptor_buffer *desc = ctx->buffer_tail;

	if (z * sizeof(*d) > desc->buffer_size)
		return NULL;

	if (z * sizeof(*d) > desc->buffer_size - desc->used) {
		/* No room for the descriptor in this buffer, so advance to the
		 * next one. */

		if (desc->list.next == &ctx->buffer_list) {
			/* If there is no free buffer next in the list,
			 * allocate one. */
			if (context_add_buffer(ctx) < 0)
				return NULL;
		}
		desc = list_entry(desc->list.next,
				struct descriptor_buffer, list);
		ctx->buffer_tail = desc;
	}

	d = desc->buffer + desc->used / sizeof(*d);
	memset(d, 0, z * sizeof(*d));
	*d_bus = desc->buffer_bus + desc->used;

	return d;
}

static void context_run(struct context *ctx, u32 extra)
{
	struct fw_ohci *ohci = ctx->ohci;

	reg_write(ohci, COMMAND_PTR(ctx->regs),
		  le32_to_cpu(ctx->last->branch_address));
	reg_write(ohci, CONTROL_CLEAR(ctx->regs), ~0);
	reg_write(ohci, CONTROL_SET(ctx->regs), CONTEXT_RUN | extra);
	flush_writes(ohci);
}

static void context_append(struct context *ctx,
			   struct descriptor *d, int z, int extra)
{
	dma_addr_t d_bus;
	struct descriptor_buffer *desc = ctx->buffer_tail;

	d_bus = desc->buffer_bus + (d - desc->buffer) * sizeof(*d);

	desc->used += (z + extra) * sizeof(*d);
	ctx->prev->branch_address = cpu_to_le32(d_bus | z);
	ctx->prev = find_branch_descriptor(d, z);

	reg_write(ctx->ohci, CONTROL_SET(ctx->regs), CONTEXT_WAKE);
	flush_writes(ctx->ohci);
}

static void context_stop(struct context *ctx)
{
	u32 reg;
	int i;

	reg_write(ctx->ohci, CONTROL_CLEAR(ctx->regs), CONTEXT_RUN);
	flush_writes(ctx->ohci);

	for (i = 0; i < 10; i++) {
		reg = reg_read(ctx->ohci, CONTROL_SET(ctx->regs));
		if ((reg & CONTEXT_ACTIVE) == 0)
			return;

		mdelay(1);
	}
	fw_error("Error: DMA context still active (0x%08x)\n", reg);
}

struct driver_data {
	struct fw_packet *packet;
};

/*
 * This function apppends a packet to the DMA queue for transmission.
 * Must always be called with the ochi->lock held to ensure proper
 * generation handling and locking around packet queue manipulation.
 */
static int at_context_queue_packet(struct context *ctx,
				   struct fw_packet *packet)
{
	struct fw_ohci *ohci = ctx->ohci;
	dma_addr_t d_bus, uninitialized_var(payload_bus);
	struct driver_data *driver_data;
	struct descriptor *d, *last;
	__le32 *header;
	int z, tcode;
	u32 reg;

	d = context_get_descriptors(ctx, 4, &d_bus);
	if (d == NULL) {
		packet->ack = RCODE_SEND_ERROR;
		return -1;
	}

	d[0].control   = cpu_to_le16(DESCRIPTOR_KEY_IMMEDIATE);
	d[0].res_count = cpu_to_le16(packet->timestamp);

	/*
	 * The DMA format for asyncronous link packets is different
	 * from the IEEE1394 layout, so shift the fields around
	 * accordingly.  If header_length is 8, it's a PHY packet, to
	 * which we need to prepend an extra quadlet.
	 */

	header = (__le32 *) &d[1];
	switch (packet->header_length) {
	case 16:
	case 12:
		header[0] = cpu_to_le32((packet->header[0] & 0xffff) |
					(packet->speed << 16));
		header[1] = cpu_to_le32((packet->header[1] & 0xffff) |
					(packet->header[0] & 0xffff0000));
		header[2] = cpu_to_le32(packet->header[2]);

		tcode = (packet->header[0] >> 4) & 0x0f;
		if (TCODE_IS_BLOCK_PACKET(tcode))
			header[3] = cpu_to_le32(packet->header[3]);
		else
			header[3] = (__force __le32) packet->header[3];

		d[0].req_count = cpu_to_le16(packet->header_length);
		break;

	case 8:
		header[0] = cpu_to_le32((OHCI1394_phy_tcode << 4) |
					(packet->speed << 16));
		header[1] = cpu_to_le32(packet->header[0]);
		header[2] = cpu_to_le32(packet->header[1]);
		d[0].req_count = cpu_to_le16(12);
		break;

	case 4:
		header[0] = cpu_to_le32((packet->header[0] & 0xffff) |
					(packet->speed << 16));
		header[1] = cpu_to_le32(packet->header[0] & 0xffff0000);
		d[0].req_count = cpu_to_le16(8);
		break;

	default:
		/* BUG(); */
		packet->ack = RCODE_SEND_ERROR;
		return -1;
	}

	driver_data = (struct driver_data *) &d[3];
	driver_data->packet = packet;
	packet->driver_data = driver_data;

	if (packet->payload_length > 0) {
		payload_bus =
			dma_map_single(ohci->card.device, packet->payload,
				       packet->payload_length, DMA_TO_DEVICE);
		if (dma_mapping_error(ohci->card.device, payload_bus)) {
			packet->ack = RCODE_SEND_ERROR;
			return -1;
		}
		packet->payload_bus	= payload_bus;
		packet->payload_mapped	= true;

		d[2].req_count    = cpu_to_le16(packet->payload_length);
		d[2].data_address = cpu_to_le32(payload_bus);
		last = &d[2];
		z = 3;
	} else {
		last = &d[0];
		z = 2;
	}

	last->control |= cpu_to_le16(DESCRIPTOR_OUTPUT_LAST |
				     DESCRIPTOR_IRQ_ALWAYS |
				     DESCRIPTOR_BRANCH_ALWAYS);

	/*
	 * If the controller and packet generations don't match, we need to
	 * bail out and try again.  If IntEvent.busReset is set, the AT context
	 * is halted, so appending to the context and trying to run it is
	 * futile.  Most controllers do the right thing and just flush the AT
	 * queue (per section 7.2.3.2 of the OHCI 1.1 specification), but
	 * some controllers (like a JMicron JMB381 PCI-e) misbehave and wind
	 * up stalling out.  So we just bail out in software and try again
	 * later, and everyone is happy.
	 * FIXME: Document how the locking works.
	 */
	if (ohci->generation != packet->generation ||
	    reg_read(ohci, OHCI1394_IntEventSet) & OHCI1394_busReset) {
		if (packet->payload_mapped)
			dma_unmap_single(ohci->card.device, payload_bus,
					 packet->payload_length, DMA_TO_DEVICE);
		packet->ack = RCODE_GENERATION;
		return -1;
	}

	context_append(ctx, d, z, 4 - z);

	/* If the context isn't already running, start it up. */
	reg = reg_read(ctx->ohci, CONTROL_SET(ctx->regs));
	if ((reg & CONTEXT_RUN) == 0)
		context_run(ctx, 0);

	return 0;
}

static int handle_at_packet(struct context *context,
			    struct descriptor *d,
			    struct descriptor *last)
{
	struct driver_data *driver_data;
	struct fw_packet *packet;
	struct fw_ohci *ohci = context->ohci;
	int evt;

	if (last->transfer_status == 0)
		/* This descriptor isn't done yet, stop iteration. */
		return 0;

	driver_data = (struct driver_data *) &d[3];
	packet = driver_data->packet;
	if (packet == NULL)
		/* This packet was cancelled, just continue. */
		return 1;

	if (packet->payload_mapped)
		dma_unmap_single(ohci->card.device, packet->payload_bus,
				 packet->payload_length, DMA_TO_DEVICE);

	evt = le16_to_cpu(last->transfer_status) & 0x1f;
	packet->timestamp = le16_to_cpu(last->res_count);

	log_ar_at_event('T', packet->speed, packet->header, evt);

	switch (evt) {
	case OHCI1394_evt_timeout:
		/* Async response transmit timed out. */
		packet->ack = RCODE_CANCELLED;
		break;

	case OHCI1394_evt_flushed:
		/*
		 * The packet was flushed should give same error as
		 * when we try to use a stale generation count.
		 */
		packet->ack = RCODE_GENERATION;
		break;

	case OHCI1394_evt_missing_ack:
		/*
		 * Using a valid (current) generation count, but the
		 * node is not on the bus or not sending acks.
		 */
		packet->ack = RCODE_NO_ACK;
		break;

	case ACK_COMPLETE + 0x10:
	case ACK_PENDING + 0x10:
	case ACK_BUSY_X + 0x10:
	case ACK_BUSY_A + 0x10:
	case ACK_BUSY_B + 0x10:
	case ACK_DATA_ERROR + 0x10:
	case ACK_TYPE_ERROR + 0x10:
		packet->ack = evt - 0x10;
		break;

	default:
		packet->ack = RCODE_SEND_ERROR;
		break;
	}

	packet->callback(packet, &ohci->card, packet->ack);

	return 1;
}

#define HEADER_GET_DESTINATION(q)	(((q) >> 16) & 0xffff)
#define HEADER_GET_TCODE(q)		(((q) >> 4) & 0x0f)
#define HEADER_GET_OFFSET_HIGH(q)	(((q) >> 0) & 0xffff)
#define HEADER_GET_DATA_LENGTH(q)	(((q) >> 16) & 0xffff)
#define HEADER_GET_EXTENDED_TCODE(q)	(((q) >> 0) & 0xffff)

static void handle_local_rom(struct fw_ohci *ohci,
			     struct fw_packet *packet, u32 csr)
{
	struct fw_packet response;
	int tcode, length, i;

	tcode = HEADER_GET_TCODE(packet->header[0]);
	if (TCODE_IS_BLOCK_PACKET(tcode))
		length = HEADER_GET_DATA_LENGTH(packet->header[3]);
	else
		length = 4;

	i = csr - CSR_CONFIG_ROM;
	if (i + length > CONFIG_ROM_SIZE) {
		fw_fill_response(&response, packet->header,
				 RCODE_ADDRESS_ERROR, NULL, 0);
	} else if (!TCODE_IS_READ_REQUEST(tcode)) {
		fw_fill_response(&response, packet->header,
				 RCODE_TYPE_ERROR, NULL, 0);
	} else {
		fw_fill_response(&response, packet->header, RCODE_COMPLETE,
				 (void *) ohci->config_rom + i, length);
	}

	fw_core_handle_response(&ohci->card, &response);
}

static void handle_local_lock(struct fw_ohci *ohci,
			      struct fw_packet *packet, u32 csr)
{
	struct fw_packet response;
	int tcode, length, ext_tcode, sel;
	__be32 *payload, lock_old;
	u32 lock_arg, lock_data;

	tcode = HEADER_GET_TCODE(packet->header[0]);
	length = HEADER_GET_DATA_LENGTH(packet->header[3]);
	payload = packet->payload;
	ext_tcode = HEADER_GET_EXTENDED_TCODE(packet->header[3]);

	if (tcode == TCODE_LOCK_REQUEST &&
	    ext_tcode == EXTCODE_COMPARE_SWAP && length == 8) {
		lock_arg = be32_to_cpu(payload[0]);
		lock_data = be32_to_cpu(payload[1]);
	} else if (tcode == TCODE_READ_QUADLET_REQUEST) {
		lock_arg = 0;
		lock_data = 0;
	} else {
		fw_fill_response(&response, packet->header,
				 RCODE_TYPE_ERROR, NULL, 0);
		goto out;
	}

	sel = (csr - CSR_BUS_MANAGER_ID) / 4;
	reg_write(ohci, OHCI1394_CSRData, lock_data);
	reg_write(ohci, OHCI1394_CSRCompareData, lock_arg);
	reg_write(ohci, OHCI1394_CSRControl, sel);

	if (reg_read(ohci, OHCI1394_CSRControl) & 0x80000000)
		lock_old = cpu_to_be32(reg_read(ohci, OHCI1394_CSRData));
	else
		fw_notify("swap not done yet\n");

	fw_fill_response(&response, packet->header,
			 RCODE_COMPLETE, &lock_old, sizeof(lock_old));
 out:
	fw_core_handle_response(&ohci->card, &response);
}

static void handle_local_request(struct context *ctx, struct fw_packet *packet)
{
	u64 offset;
	u32 csr;

	if (ctx == &ctx->ohci->at_request_ctx) {
		packet->ack = ACK_PENDING;
		packet->callback(packet, &ctx->ohci->card, packet->ack);
	}

	offset =
		((unsigned long long)
		 HEADER_GET_OFFSET_HIGH(packet->header[1]) << 32) |
		packet->header[2];
	csr = offset - CSR_REGISTER_BASE;

	/* Handle config rom reads. */
	if (csr >= CSR_CONFIG_ROM && csr < CSR_CONFIG_ROM_END)
		handle_local_rom(ctx->ohci, packet, csr);
	else switch (csr) {
	case CSR_BUS_MANAGER_ID:
	case CSR_BANDWIDTH_AVAILABLE:
	case CSR_CHANNELS_AVAILABLE_HI:
	case CSR_CHANNELS_AVAILABLE_LO:
		handle_local_lock(ctx->ohci, packet, csr);
		break;
	default:
		if (ctx == &ctx->ohci->at_request_ctx)
			fw_core_handle_request(&ctx->ohci->card, packet);
		else
			fw_core_handle_response(&ctx->ohci->card, packet);
		break;
	}

	if (ctx == &ctx->ohci->at_response_ctx) {
		packet->ack = ACK_COMPLETE;
		packet->callback(packet, &ctx->ohci->card, packet->ack);
	}
}

static void at_context_transmit(struct context *ctx, struct fw_packet *packet)
{
	unsigned long flags;
	int ret;

	spin_lock_irqsave(&ctx->ohci->lock, flags);

	if (HEADER_GET_DESTINATION(packet->header[0]) == ctx->ohci->node_id &&
	    ctx->ohci->generation == packet->generation) {
		spin_unlock_irqrestore(&ctx->ohci->lock, flags);
		handle_local_request(ctx, packet);
		return;
	}

	ret = at_context_queue_packet(ctx, packet);
	spin_unlock_irqrestore(&ctx->ohci->lock, flags);

	if (ret < 0)
		packet->callback(packet, &ctx->ohci->card, packet->ack);

}

static void bus_reset_tasklet(unsigned long data)
{
	struct fw_ohci *ohci = (struct fw_ohci *)data;
	int self_id_count, i, j, reg;
	int generation, new_generation;
	unsigned long flags;
	void *free_rom = NULL;
	dma_addr_t free_rom_bus = 0;

	reg = reg_read(ohci, OHCI1394_NodeID);
	if (!(reg & OHCI1394_NodeID_idValid)) {
		fw_notify("node ID not valid, new bus reset in progress\n");
		return;
	}
	if ((reg & OHCI1394_NodeID_nodeNumber) == 63) {
		fw_notify("malconfigured bus\n");
		return;
	}
	ohci->node_id = reg & (OHCI1394_NodeID_busNumber |
			       OHCI1394_NodeID_nodeNumber);

	reg = reg_read(ohci, OHCI1394_SelfIDCount);
	if (reg & OHCI1394_SelfIDCount_selfIDError) {
		fw_notify("inconsistent self IDs\n");
		return;
	}
	/*
	 * The count in the SelfIDCount register is the number of
	 * bytes in the self ID receive buffer.  Since we also receive
	 * the inverted quadlets and a header quadlet, we shift one
	 * bit extra to get the actual number of self IDs.
	 */
	self_id_count = (reg >> 3) & 0xff;
	if (self_id_count == 0 || self_id_count > 252) {
		fw_notify("inconsistent self IDs\n");
		return;
	}
	generation = (cond_le32_to_cpu(ohci->self_id_cpu[0]) >> 16) & 0xff;
	rmb();

	for (i = 1, j = 0; j < self_id_count; i += 2, j++) {
		if (ohci->self_id_cpu[i] != ~ohci->self_id_cpu[i + 1]) {
			fw_notify("inconsistent self IDs\n");
			return;
		}
		ohci->self_id_buffer[j] =
				cond_le32_to_cpu(ohci->self_id_cpu[i]);
	}
	rmb();

	/*
	 * Check the consistency of the self IDs we just read.  The
	 * problem we face is that a new bus reset can start while we
	 * read out the self IDs from the DMA buffer. If this happens,
	 * the DMA buffer will be overwritten with new self IDs and we
	 * will read out inconsistent data.  The OHCI specification
	 * (section 11.2) recommends a technique similar to
	 * linux/seqlock.h, where we remember the generation of the
	 * self IDs in the buffer before reading them out and compare
	 * it to the current generation after reading them out.  If
	 * the two generations match we know we have a consistent set
	 * of self IDs.
	 */

	new_generation = (reg_read(ohci, OHCI1394_SelfIDCount) >> 16) & 0xff;
	if (new_generation != generation) {
		fw_notify("recursive bus reset detected, "
			  "discarding self ids\n");
		return;
	}

	/* FIXME: Document how the locking works. */
	spin_lock_irqsave(&ohci->lock, flags);

	ohci->generation = generation;
	context_stop(&ohci->at_request_ctx);
	context_stop(&ohci->at_response_ctx);
	reg_write(ohci, OHCI1394_IntEventClear, OHCI1394_busReset);

	if (ohci->bus_reset_packet_quirk)
		ohci->request_generation = generation;

	/*
	 * This next bit is unrelated to the AT context stuff but we
	 * have to do it under the spinlock also.  If a new config rom
	 * was set up before this reset, the old one is now no longer
	 * in use and we can free it. Update the config rom pointers
	 * to point to the current config rom and clear the
	 * next_config_rom pointer so a new udpate can take place.
	 */

	if (ohci->next_config_rom != NULL) {
		if (ohci->next_config_rom != ohci->config_rom) {
			free_rom      = ohci->config_rom;
			free_rom_bus  = ohci->config_rom_bus;
		}
		ohci->config_rom      = ohci->next_config_rom;
		ohci->config_rom_bus  = ohci->next_config_rom_bus;
		ohci->next_config_rom = NULL;

		/*
		 * Restore config_rom image and manually update
		 * config_rom registers.  Writing the header quadlet
		 * will indicate that the config rom is ready, so we
		 * do that last.
		 */
		reg_write(ohci, OHCI1394_BusOptions,
			  be32_to_cpu(ohci->config_rom[2]));
		ohci->config_rom[0] = ohci->next_header;
		reg_write(ohci, OHCI1394_ConfigROMhdr,
			  be32_to_cpu(ohci->next_header));
	}

#ifdef CONFIG_FIREWIRE_OHCI_REMOTE_DMA
	reg_write(ohci, OHCI1394_PhyReqFilterHiSet, ~0);
	reg_write(ohci, OHCI1394_PhyReqFilterLoSet, ~0);
#endif

	spin_unlock_irqrestore(&ohci->lock, flags);

	if (free_rom)
		dma_free_coherent(ohci->card.device, CONFIG_ROM_SIZE,
				  free_rom, free_rom_bus);

	log_selfids(ohci->node_id, generation,
		    self_id_count, ohci->self_id_buffer);

	fw_core_handle_bus_reset(&ohci->card, ohci->node_id, generation,
				 self_id_count, ohci->self_id_buffer);
}

static irqreturn_t irq_handler(int irq, void *data)
{
	struct fw_ohci *ohci = data;
	u32 event, iso_event;
	int i;

	event = reg_read(ohci, OHCI1394_IntEventClear);

	if (!event || !~event)
		return IRQ_NONE;

	/* busReset must not be cleared yet, see OHCI 1.1 clause 7.2.3.2 */
	reg_write(ohci, OHCI1394_IntEventClear, event & ~OHCI1394_busReset);
	log_irqs(event);

	if (event & OHCI1394_selfIDComplete)
		tasklet_schedule(&ohci->bus_reset_tasklet);

	if (event & OHCI1394_RQPkt)
		tasklet_schedule(&ohci->ar_request_ctx.tasklet);

	if (event & OHCI1394_RSPkt)
		tasklet_schedule(&ohci->ar_response_ctx.tasklet);

	if (event & OHCI1394_reqTxComplete)
		tasklet_schedule(&ohci->at_request_ctx.tasklet);

	if (event & OHCI1394_respTxComplete)
		tasklet_schedule(&ohci->at_response_ctx.tasklet);

	iso_event = reg_read(ohci, OHCI1394_IsoRecvIntEventClear);
	reg_write(ohci, OHCI1394_IsoRecvIntEventClear, iso_event);

	while (iso_event) {
		i = ffs(iso_event) - 1;
		tasklet_schedule(&ohci->ir_context_list[i].context.tasklet);
		iso_event &= ~(1 << i);
	}

	iso_event = reg_read(ohci, OHCI1394_IsoXmitIntEventClear);
	reg_write(ohci, OHCI1394_IsoXmitIntEventClear, iso_event);

	while (iso_event) {
		i = ffs(iso_event) - 1;
		tasklet_schedule(&ohci->it_context_list[i].context.tasklet);
		iso_event &= ~(1 << i);
	}

	if (unlikely(event & OHCI1394_regAccessFail))
		fw_error("Register access failure - "
			 "please notify linux1394-devel@lists.sf.net\n");

	if (unlikely(event & OHCI1394_postedWriteErr))
		fw_error("PCI posted write error\n");

	if (unlikely(event & OHCI1394_cycleTooLong)) {
		if (printk_ratelimit())
			fw_notify("isochronous cycle too long\n");
		reg_write(ohci, OHCI1394_LinkControlSet,
			  OHCI1394_LinkControl_cycleMaster);
	}

	if (unlikely(event & OHCI1394_cycleInconsistent)) {
		/*
		 * We need to clear this event bit in order to make
		 * cycleMatch isochronous I/O work.  In theory we should
		 * stop active cycleMatch iso contexts now and restart
		 * them at least two cycles later.  (FIXME?)
		 */
		if (printk_ratelimit())
			fw_notify("isochronous cycle inconsistent\n");
	}

	return IRQ_HANDLED;
}

static int software_reset(struct fw_ohci *ohci)
{
	int i;

	reg_write(ohci, OHCI1394_HCControlSet, OHCI1394_HCControl_softReset);

	for (i = 0; i < OHCI_LOOP_COUNT; i++) {
		if ((reg_read(ohci, OHCI1394_HCControlSet) &
		     OHCI1394_HCControl_softReset) == 0)
			return 0;
		msleep(1);
	}

	return -EBUSY;
}

static void copy_config_rom(__be32 *dest, const __be32 *src, size_t length)
{
	size_t size = length * 4;

	memcpy(dest, src, size);
	if (size < CONFIG_ROM_SIZE)
		memset(&dest[length], 0, CONFIG_ROM_SIZE - size);
}

static int ohci_enable(struct fw_card *card,
		       const __be32 *config_rom, size_t length)
{
	struct fw_ohci *ohci = fw_ohci(card);
	struct pci_dev *dev = to_pci_dev(card->device);
	u32 lps;
	int i;

	if (software_reset(ohci)) {
		fw_error("Failed to reset ohci card.\n");
		return -EBUSY;
	}

	/*
	 * Now enable LPS, which we need in order to start accessing
	 * most of the registers.  In fact, on some cards (ALI M5251),
	 * accessing registers in the SClk domain without LPS enabled
	 * will lock up the machine.  Wait 50msec to make sure we have
	 * full link enabled.  However, with some cards (well, at least
	 * a JMicron PCIe card), we have to try again sometimes.
	 */
	reg_write(ohci, OHCI1394_HCControlSet,
		  OHCI1394_HCControl_LPS |
		  OHCI1394_HCControl_postedWriteEnable);
	flush_writes(ohci);

	for (lps = 0, i = 0; !lps && i < 3; i++) {
		msleep(50);
		lps = reg_read(ohci, OHCI1394_HCControlSet) &
		      OHCI1394_HCControl_LPS;
	}

	if (!lps) {
		fw_error("Failed to set Link Power Status\n");
		return -EIO;
	}

	reg_write(ohci, OHCI1394_HCControlClear,
		  OHCI1394_HCControl_noByteSwapData);

	reg_write(ohci, OHCI1394_SelfIDBuffer, ohci->self_id_bus);
	reg_write(ohci, OHCI1394_LinkControlClear,
		  OHCI1394_LinkControl_rcvPhyPkt);
	reg_write(ohci, OHCI1394_LinkControlSet,
		  OHCI1394_LinkControl_rcvSelfID |
		  OHCI1394_LinkControl_cycleTimerEnable |
		  OHCI1394_LinkControl_cycleMaster);

	reg_write(ohci, OHCI1394_ATRetries,
		  OHCI1394_MAX_AT_REQ_RETRIES |
		  (OHCI1394_MAX_AT_RESP_RETRIES << 4) |
		  (OHCI1394_MAX_PHYS_RESP_RETRIES << 8));

	ar_context_run(&ohci->ar_request_ctx);
	ar_context_run(&ohci->ar_response_ctx);

	reg_write(ohci, OHCI1394_PhyUpperBound, 0x00010000);
	reg_write(ohci, OHCI1394_IntEventClear, ~0);
	reg_write(ohci, OHCI1394_IntMaskClear, ~0);
	reg_write(ohci, OHCI1394_IntMaskSet,
		  OHCI1394_selfIDComplete |
		  OHCI1394_RQPkt | OHCI1394_RSPkt |
		  OHCI1394_reqTxComplete | OHCI1394_respTxComplete |
		  OHCI1394_isochRx | OHCI1394_isochTx |
		  OHCI1394_postedWriteErr | OHCI1394_cycleTooLong |
		  OHCI1394_cycleInconsistent | OHCI1394_regAccessFail |
		  OHCI1394_masterIntEnable);
	if (param_debug & OHCI_PARAM_DEBUG_BUSRESETS)
		reg_write(ohci, OHCI1394_IntMaskSet, OHCI1394_busReset);

	/* Activate link_on bit and contender bit in our self ID packets.*/
	if (ohci_update_phy_reg(card, 4, 0,
				PHY_LINK_ACTIVE | PHY_CONTENDER) < 0)
		return -EIO;

	/*
	 * When the link is not yet enabled, the atomic config rom
	 * update mechanism described below in ohci_set_config_rom()
	 * is not active.  We have to update ConfigRomHeader and
	 * BusOptions manually, and the write to ConfigROMmap takes
	 * effect immediately.  We tie this to the enabling of the
	 * link, so we have a valid config rom before enabling - the
	 * OHCI requires that ConfigROMhdr and BusOptions have valid
	 * values before enabling.
	 *
	 * However, when the ConfigROMmap is written, some controllers
	 * always read back quadlets 0 and 2 from the config rom to
	 * the ConfigRomHeader and BusOptions registers on bus reset.
	 * They shouldn't do that in this initial case where the link
	 * isn't enabled.  This means we have to use the same
	 * workaround here, setting the bus header to 0 and then write
	 * the right values in the bus reset tasklet.
	 */

	if (config_rom) {
		ohci->next_config_rom =
			dma_alloc_coherent(ohci->card.device, CONFIG_ROM_SIZE,
					   &ohci->next_config_rom_bus,
					   GFP_KERNEL);
		if (ohci->next_config_rom == NULL)
			return -ENOMEM;

		copy_config_rom(ohci->next_config_rom, config_rom, length);
	} else {
		/*
		 * In the suspend case, config_rom is NULL, which
		 * means that we just reuse the old config rom.
		 */
		ohci->next_config_rom = ohci->config_rom;
		ohci->next_config_rom_bus = ohci->config_rom_bus;
	}

	ohci->next_header = ohci->next_config_rom[0];
	ohci->next_config_rom[0] = 0;
	reg_write(ohci, OHCI1394_ConfigROMhdr, 0);
	reg_write(ohci, OHCI1394_BusOptions,
		  be32_to_cpu(ohci->next_config_rom[2]));
	reg_write(ohci, OHCI1394_ConfigROMmap, ohci->next_config_rom_bus);

	reg_write(ohci, OHCI1394_AsReqFilterHiSet, 0x80000000);

	if (request_irq(dev->irq, irq_handler,
			IRQF_SHARED, ohci_driver_name, ohci)) {
		fw_error("Failed to allocate shared interrupt %d.\n",
			 dev->irq);
		dma_free_coherent(ohci->card.device, CONFIG_ROM_SIZE,
				  ohci->config_rom, ohci->config_rom_bus);
		return -EIO;
	}

	reg_write(ohci, OHCI1394_HCControlSet,
		  OHCI1394_HCControl_linkEnable |
		  OHCI1394_HCControl_BIBimageValid);
	flush_writes(ohci);

	/*
	 * We are ready to go, initiate bus reset to finish the
	 * initialization.
	 */

	fw_core_initiate_bus_reset(&ohci->card, 1);

	return 0;
}

static int ohci_set_config_rom(struct fw_card *card,
			       const __be32 *config_rom, size_t length)
{
	struct fw_ohci *ohci;
	unsigned long flags;
	int ret = -EBUSY;
	__be32 *next_config_rom;
	dma_addr_t uninitialized_var(next_config_rom_bus);

	ohci = fw_ohci(card);

	/*
	 * When the OHCI controller is enabled, the config rom update
	 * mechanism is a bit tricky, but easy enough to use.  See
	 * section 5.5.6 in the OHCI specification.
	 *
	 * The OHCI controller caches the new config rom address in a
	 * shadow register (ConfigROMmapNext) and needs a bus reset
	 * for the changes to take place.  When the bus reset is
	 * detected, the controller loads the new values for the
	 * ConfigRomHeader and BusOptions registers from the specified
	 * config rom and loads ConfigROMmap from the ConfigROMmapNext
	 * shadow register. All automatically and atomically.
	 *
	 * Now, there's a twist to this story.  The automatic load of
	 * ConfigRomHeader and BusOptions doesn't honor the
	 * noByteSwapData bit, so with a be32 config rom, the
	 * controller will load be32 values in to these registers
	 * during the atomic update, even on litte endian
	 * architectures.  The workaround we use is to put a 0 in the
	 * header quadlet; 0 is endian agnostic and means that the
	 * config rom isn't ready yet.  In the bus reset tasklet we
	 * then set up the real values for the two registers.
	 *
	 * We use ohci->lock to avoid racing with the code that sets
	 * ohci->next_config_rom to NULL (see bus_reset_tasklet).
	 */

	next_config_rom =
		dma_alloc_coherent(ohci->card.device, CONFIG_ROM_SIZE,
				   &next_config_rom_bus, GFP_KERNEL);
	if (next_config_rom == NULL)
		return -ENOMEM;

	spin_lock_irqsave(&ohci->lock, flags);

	if (ohci->next_config_rom == NULL) {
		ohci->next_config_rom = next_config_rom;
		ohci->next_config_rom_bus = next_config_rom_bus;

		copy_config_rom(ohci->next_config_rom, config_rom, length);

		ohci->next_header = config_rom[0];
		ohci->next_config_rom[0] = 0;

		reg_write(ohci, OHCI1394_ConfigROMmap,
			  ohci->next_config_rom_bus);
		ret = 0;
	}

	spin_unlock_irqrestore(&ohci->lock, flags);

	/*
	 * Now initiate a bus reset to have the changes take
	 * effect. We clean up the old config rom memory and DMA
	 * mappings in the bus reset tasklet, since the OHCI
	 * controller could need to access it before the bus reset
	 * takes effect.
	 */
	if (ret == 0)
		fw_core_initiate_bus_reset(&ohci->card, 1);
	else
		dma_free_coherent(ohci->card.device, CONFIG_ROM_SIZE,
				  next_config_rom, next_config_rom_bus);

	return ret;
}

static void ohci_send_request(struct fw_card *card, struct fw_packet *packet)
{
	struct fw_ohci *ohci = fw_ohci(card);

	at_context_transmit(&ohci->at_request_ctx, packet);
}

static void ohci_send_response(struct fw_card *card, struct fw_packet *packet)
{
	struct fw_ohci *ohci = fw_ohci(card);

	at_context_transmit(&ohci->at_response_ctx, packet);
}

static int ohci_cancel_packet(struct fw_card *card, struct fw_packet *packet)
{
	struct fw_ohci *ohci = fw_ohci(card);
	struct context *ctx = &ohci->at_request_ctx;
	struct driver_data *driver_data = packet->driver_data;
	int ret = -ENOENT;

	tasklet_disable(&ctx->tasklet);

	if (packet->ack != 0)
		goto out;

	if (packet->payload_mapped)
		dma_unmap_single(ohci->card.device, packet->payload_bus,
				 packet->payload_length, DMA_TO_DEVICE);

	log_ar_at_event('T', packet->speed, packet->header, 0x20);
	driver_data->packet = NULL;
	packet->ack = RCODE_CANCELLED;
	packet->callback(packet, &ohci->card, packet->ack);
	ret = 0;
 out:
	tasklet_enable(&ctx->tasklet);

	return ret;
}

static int ohci_enable_phys_dma(struct fw_card *card,
				int node_id, int generation)
{
#ifdef CONFIG_FIREWIRE_OHCI_REMOTE_DMA
	return 0;
#else
	struct fw_ohci *ohci = fw_ohci(card);
	unsigned long flags;
	int n, ret = 0;

	/*
	 * FIXME:  Make sure this bitmask is cleared when we clear the busReset
	 * interrupt bit.  Clear physReqResourceAllBuses on bus reset.
	 */

	spin_lock_irqsave(&ohci->lock, flags);

	if (ohci->generation != generation) {
		ret = -ESTALE;
		goto out;
	}

	/*
	 * Note, if the node ID contains a non-local bus ID, physical DMA is
	 * enabled for _all_ nodes on remote buses.
	 */

	n = (node_id & 0xffc0) == LOCAL_BUS ? node_id & 0x3f : 63;
	if (n < 32)
		reg_write(ohci, OHCI1394_PhyReqFilterLoSet, 1 << n);
	else
		reg_write(ohci, OHCI1394_PhyReqFilterHiSet, 1 << (n - 32));

	flush_writes(ohci);
 out:
	spin_unlock_irqrestore(&ohci->lock, flags);

	return ret;
#endif /* CONFIG_FIREWIRE_OHCI_REMOTE_DMA */
}

static u32 cycle_timer_ticks(u32 cycle_timer)
{
	u32 ticks;

	ticks = cycle_timer & 0xfff;
	ticks += 3072 * ((cycle_timer >> 12) & 0x1fff);
	ticks += (3072 * 8000) * (cycle_timer >> 25);

	return ticks;
}

/*
 * Some controllers exhibit one or more of the following bugs when updating the
 * iso cycle timer register:
 *  - When the lowest six bits are wrapping around to zero, a read that happens
 *    at the same time will return garbage in the lowest ten bits.
 *  - When the cycleOffset field wraps around to zero, the cycleCount field is
 *    not incremented for about 60 ns.
 *  - Occasionally, the entire register reads zero.
 *
 * To catch these, we read the register three times and ensure that the
 * difference between each two consecutive reads is approximately the same, i.e.
 * less than twice the other.  Furthermore, any negative difference indicates an
 * error.  (A PCI read should take at least 20 ticks of the 24.576 MHz timer to
 * execute, so we have enough precision to compute the ratio of the differences.)
 */
static u32 ohci_get_cycle_time(struct fw_card *card)
{
	struct fw_ohci *ohci = fw_ohci(card);
	u32 c0, c1, c2;
	u32 t0, t1, t2;
	s32 diff01, diff12;
	int i;

	c2 = reg_read(ohci, OHCI1394_IsochronousCycleTimer);

	if (ohci->iso_cycle_timer_quirk) {
		i = 0;
		c1 = c2;
		c2 = reg_read(ohci, OHCI1394_IsochronousCycleTimer);
		do {
			c0 = c1;
			c1 = c2;
			c2 = reg_read(ohci, OHCI1394_IsochronousCycleTimer);
			t0 = cycle_timer_ticks(c0);
			t1 = cycle_timer_ticks(c1);
			t2 = cycle_timer_ticks(c2);
			diff01 = t1 - t0;
			diff12 = t2 - t1;
		} while ((diff01 <= 0 || diff12 <= 0 ||
			  diff01 / diff12 >= 2 || diff12 / diff01 >= 2)
			 && i++ < 20);
	}

	return c2;
}

static void copy_iso_headers(struct iso_context *ctx, void *p)
{
	int i = ctx->header_length;

	if (i + ctx->base.header_size > PAGE_SIZE)
		return;

	/*
	 * The iso header is byteswapped to little endian by
	 * the controller, but the remaining header quadlets
	 * are big endian.  We want to present all the headers
	 * as big endian, so we have to swap the first quadlet.
	 */
	if (ctx->base.header_size > 0)
		*(u32 *) (ctx->header + i) = __swab32(*(u32 *) (p + 4));
	if (ctx->base.header_size > 4)
		*(u32 *) (ctx->header + i + 4) = __swab32(*(u32 *) p);
	if (ctx->base.header_size > 8)
		memcpy(ctx->header + i + 8, p + 8, ctx->base.header_size - 8);
	ctx->header_length += ctx->base.header_size;
}

static int handle_ir_packet_per_buffer(struct context *context,
				       struct descriptor *d,
				       struct descriptor *last)
{
	struct iso_context *ctx =
		container_of(context, struct iso_context, context);
	struct descriptor *pd;
	__le32 *ir_header;
	void *p;

	for (pd = d; pd <= last; pd++) {
		if (pd->transfer_status)
			break;
	}
	if (pd > last)
		/* Descriptor(s) not done yet, stop iteration */
		return 0;

	p = last + 1;
	copy_iso_headers(ctx, p);

	if (le16_to_cpu(last->control) & DESCRIPTOR_IRQ_ALWAYS) {
		ir_header = (__le32 *) p;
		ctx->base.callback(&ctx->base,
				   le32_to_cpu(ir_header[0]) & 0xffff,
				   ctx->header_length, ctx->header,
				   ctx->base.callback_data);
		ctx->header_length = 0;
	}

	return 1;
}

static int handle_it_packet(struct context *context,
			    struct descriptor *d,
			    struct descriptor *last)
{
	struct iso_context *ctx =
		container_of(context, struct iso_context, context);
	int i;
	struct descriptor *pd;

	for (pd = d; pd <= last; pd++)
		if (pd->transfer_status)
			break;
	if (pd > last)
		/* Descriptor(s) not done yet, stop iteration */
		return 0;

	i = ctx->header_length;
	if (i + 4 < PAGE_SIZE) {
		/* Present this value as big-endian to match the receive code */
		*(__be32 *)(ctx->header + i) = cpu_to_be32(
				((u32)le16_to_cpu(pd->transfer_status) << 16) |
				le16_to_cpu(pd->res_count));
		ctx->header_length += 4;
	}
	if (le16_to_cpu(last->control) & DESCRIPTOR_IRQ_ALWAYS) {
		ctx->base.callback(&ctx->base, le16_to_cpu(last->res_count),
				   ctx->header_length, ctx->header,
				   ctx->base.callback_data);
		ctx->header_length = 0;
	}
	return 1;
}

static struct fw_iso_context *ohci_allocate_iso_context(struct fw_card *card,
				int type, int channel, size_t header_size)
{
	struct fw_ohci *ohci = fw_ohci(card);
	struct iso_context *ctx, *list;
	descriptor_callback_t callback;
	u64 *channels, dont_care = ~0ULL;
	u32 *mask, regs;
	unsigned long flags;
	int index, ret = -ENOMEM;

	if (type == FW_ISO_CONTEXT_TRANSMIT) {
		channels = &dont_care;
		mask = &ohci->it_context_mask;
		list = ohci->it_context_list;
		callback = handle_it_packet;
	} else {
		channels = &ohci->ir_context_channels;
		mask = &ohci->ir_context_mask;
		list = ohci->ir_context_list;
		callback = handle_ir_packet_per_buffer;
	}

	spin_lock_irqsave(&ohci->lock, flags);
	index = *channels & 1ULL << channel ? ffs(*mask) - 1 : -1;
	if (index >= 0) {
		*channels &= ~(1ULL << channel);
		*mask &= ~(1 << index);
	}
	spin_unlock_irqrestore(&ohci->lock, flags);

	if (index < 0)
		return ERR_PTR(-EBUSY);

	if (type == FW_ISO_CONTEXT_TRANSMIT)
		regs = OHCI1394_IsoXmitContextBase(index);
	else
		regs = OHCI1394_IsoRcvContextBase(index);

	ctx = &list[index];
	memset(ctx, 0, sizeof(*ctx));
	ctx->header_length = 0;
	ctx->header = (void *) __get_free_page(GFP_KERNEL);
	if (ctx->header == NULL)
		goto out;

	ret = context_init(&ctx->context, ohci, regs, callback);
	if (ret < 0)
		goto out_with_header;

	return &ctx->base;

 out_with_header:
	free_page((unsigned long)ctx->header);
 out:
	spin_lock_irqsave(&ohci->lock, flags);
	*mask |= 1 << index;
	spin_unlock_irqrestore(&ohci->lock, flags);

	return ERR_PTR(ret);
}

static int ohci_start_iso(struct fw_iso_context *base,
			  s32 cycle, u32 sync, u32 tags)
{
	struct iso_context *ctx = container_of(base, struct iso_context, base);
	struct fw_ohci *ohci = ctx->context.ohci;
	u32 control, match;
	int index;

	if (ctx->base.type == FW_ISO_CONTEXT_TRANSMIT) {
		index = ctx - ohci->it_context_list;
		match = 0;
		if (cycle >= 0)
			match = IT_CONTEXT_CYCLE_MATCH_ENABLE |
				(cycle & 0x7fff) << 16;

		reg_write(ohci, OHCI1394_IsoXmitIntEventClear, 1 << index);
		reg_write(ohci, OHCI1394_IsoXmitIntMaskSet, 1 << index);
		context_run(&ctx->context, match);
	} else {
		index = ctx - ohci->ir_context_list;
		control = IR_CONTEXT_ISOCH_HEADER;
		match = (tags << 28) | (sync << 8) | ctx->base.channel;
		if (cycle >= 0) {
			match |= (cycle & 0x07fff) << 12;
			control |= IR_CONTEXT_CYCLE_MATCH_ENABLE;
		}

		reg_write(ohci, OHCI1394_IsoRecvIntEventClear, 1 << index);
		reg_write(ohci, OHCI1394_IsoRecvIntMaskSet, 1 << index);
		reg_write(ohci, CONTEXT_MATCH(ctx->context.regs), match);
		context_run(&ctx->context, control);
	}

	return 0;
}

static int ohci_stop_iso(struct fw_iso_context *base)
{
	struct fw_ohci *ohci = fw_ohci(base->card);
	struct iso_context *ctx = container_of(base, struct iso_context, base);
	int index;

	if (ctx->base.type == FW_ISO_CONTEXT_TRANSMIT) {
		index = ctx - ohci->it_context_list;
		reg_write(ohci, OHCI1394_IsoXmitIntMaskClear, 1 << index);
	} else {
		index = ctx - ohci->ir_context_list;
		reg_write(ohci, OHCI1394_IsoRecvIntMaskClear, 1 << index);
	}
	flush_writes(ohci);
	context_stop(&ctx->context);

	return 0;
}

static void ohci_free_iso_context(struct fw_iso_context *base)
{
	struct fw_ohci *ohci = fw_ohci(base->card);
	struct iso_context *ctx = container_of(base, struct iso_context, base);
	unsigned long flags;
	int index;

	ohci_stop_iso(base);
	context_release(&ctx->context);
	free_page((unsigned long)ctx->header);

	spin_lock_irqsave(&ohci->lock, flags);

	if (ctx->base.type == FW_ISO_CONTEXT_TRANSMIT) {
		index = ctx - ohci->it_context_list;
		ohci->it_context_mask |= 1 << index;
	} else {
		index = ctx - ohci->ir_context_list;
		ohci->ir_context_mask |= 1 << index;
		ohci->ir_context_channels |= 1ULL << base->channel;
	}

	spin_unlock_irqrestore(&ohci->lock, flags);
}

static int ohci_queue_iso_transmit(struct fw_iso_context *base,
				   struct fw_iso_packet *packet,
				   struct fw_iso_buffer *buffer,
				   unsigned long payload)
{
	struct iso_context *ctx = container_of(base, struct iso_context, base);
	struct descriptor *d, *last, *pd;
	struct fw_iso_packet *p;
	__le32 *header;
	dma_addr_t d_bus, page_bus;
	u32 z, header_z, payload_z, irq;
	u32 payload_index, payload_end_index, next_page_index;
	int page, end_page, i, length, offset;

	p = packet;
	payload_index = payload;

	if (p->skip)
		z = 1;
	else
		z = 2;
	if (p->header_length > 0)
		z++;

	/* Determine the first page the payload isn't contained in. */
	end_page = PAGE_ALIGN(payload_index + p->payload_length) >> PAGE_SHIFT;
	if (p->payload_length > 0)
		payload_z = end_page - (payload_index >> PAGE_SHIFT);
	else
		payload_z = 0;

	z += payload_z;

	/* Get header size in number of descriptors. */
	header_z = DIV_ROUND_UP(p->header_length, sizeof(*d));

	d = context_get_descriptors(&ctx->context, z + header_z, &d_bus);
	if (d == NULL)
		return -ENOMEM;

	if (!p->skip) {
		d[0].control   = cpu_to_le16(DESCRIPTOR_KEY_IMMEDIATE);
		d[0].req_count = cpu_to_le16(8);
		/*
		 * Link the skip address to this descriptor itself.  This causes
		 * a context to skip a cycle whenever lost cycles or FIFO
		 * overruns occur, without dropping the data.  The application
		 * should then decide whether this is an error condition or not.
		 * FIXME:  Make the context's cycle-lost behaviour configurable?
		 */
		d[0].branch_address = cpu_to_le32(d_bus | z);

		header = (__le32 *) &d[1];
		header[0] = cpu_to_le32(IT_HEADER_SY(p->sy) |
					IT_HEADER_TAG(p->tag) |
					IT_HEADER_TCODE(TCODE_STREAM_DATA) |
					IT_HEADER_CHANNEL(ctx->base.channel) |
					IT_HEADER_SPEED(ctx->base.speed));
		header[1] =
			cpu_to_le32(IT_HEADER_DATA_LENGTH(p->header_length +
							  p->payload_length));
	}

	if (p->header_length > 0) {
		d[2].req_count    = cpu_to_le16(p->header_length);
		d[2].data_address = cpu_to_le32(d_bus + z * sizeof(*d));
		memcpy(&d[z], p->header, p->header_length);
	}

	pd = d + z - payload_z;
	payload_end_index = payload_index + p->payload_length;
	for (i = 0; i < payload_z; i++) {
		page               = payload_index >> PAGE_SHIFT;
		offset             = payload_index & ~PAGE_MASK;
		next_page_index    = (page + 1) << PAGE_SHIFT;
		length             =
			min(next_page_index, payload_end_index) - payload_index;
		pd[i].req_count    = cpu_to_le16(length);

		page_bus = page_private(buffer->pages[page]);
		pd[i].data_address = cpu_to_le32(page_bus + offset);

		payload_index += length;
	}

	if (p->interrupt)
		irq = DESCRIPTOR_IRQ_ALWAYS;
	else
		irq = DESCRIPTOR_NO_IRQ;

	last = z == 2 ? d : d + z - 1;
	last->control |= cpu_to_le16(DESCRIPTOR_OUTPUT_LAST |
				     DESCRIPTOR_STATUS |
				     DESCRIPTOR_BRANCH_ALWAYS |
				     irq);

	context_append(&ctx->context, d, z, header_z);

	return 0;
}

static int ohci_queue_iso_receive_packet_per_buffer(struct fw_iso_context *base,
					struct fw_iso_packet *packet,
					struct fw_iso_buffer *buffer,
					unsigned long payload)
{
	struct iso_context *ctx = container_of(base, struct iso_context, base);
	struct descriptor *d, *pd;
	struct fw_iso_packet *p = packet;
	dma_addr_t d_bus, page_bus;
	u32 z, header_z, rest;
	int i, j, length;
	int page, offset, packet_count, header_size, payload_per_buffer;

	/*
	 * The OHCI controller puts the isochronous header and trailer in the
	 * buffer, so we need at least 8 bytes.
	 */
	packet_count = p->header_length / ctx->base.header_size;
	header_size  = max(ctx->base.header_size, (size_t)8);

	/* Get header size in number of descriptors. */
	header_z = DIV_ROUND_UP(header_size, sizeof(*d));
	page     = payload >> PAGE_SHIFT;
	offset   = payload & ~PAGE_MASK;
	payload_per_buffer = p->payload_length / packet_count;

	for (i = 0; i < packet_count; i++) {
		/* d points to the header descriptor */
		z = DIV_ROUND_UP(payload_per_buffer + offset, PAGE_SIZE) + 1;
		d = context_get_descriptors(&ctx->context,
				z + header_z, &d_bus);
		if (d == NULL)
			return -ENOMEM;

		d->control      = cpu_to_le16(DESCRIPTOR_STATUS |
					      DESCRIPTOR_INPUT_MORE);
		if (p->skip && i == 0)
			d->control |= cpu_to_le16(DESCRIPTOR_WAIT);
		d->req_count    = cpu_to_le16(header_size);
		d->res_count    = d->req_count;
		d->transfer_status = 0;
		d->data_address = cpu_to_le32(d_bus + (z * sizeof(*d)));

		rest = payload_per_buffer;
		pd = d;
		for (j = 1; j < z; j++) {
			pd++;
			pd->control = cpu_to_le16(DESCRIPTOR_STATUS |
						  DESCRIPTOR_INPUT_MORE);

			if (offset + rest < PAGE_SIZE)
				length = rest;
			else
				length = PAGE_SIZE - offset;
			pd->req_count = cpu_to_le16(length);
			pd->res_count = pd->req_count;
			pd->transfer_status = 0;

			page_bus = page_private(buffer->pages[page]);
			pd->data_address = cpu_to_le32(page_bus + offset);

			offset = (offset + length) & ~PAGE_MASK;
			rest -= length;
			if (offset == 0)
				page++;
		}
		pd->control = cpu_to_le16(DESCRIPTOR_STATUS |
					  DESCRIPTOR_INPUT_LAST |
					  DESCRIPTOR_BRANCH_ALWAYS);
		if (p->interrupt && i == packet_count - 1)
			pd->control |= cpu_to_le16(DESCRIPTOR_IRQ_ALWAYS);

		context_append(&ctx->context, d, z, header_z);
	}

	return 0;
}

static int ohci_queue_iso(struct fw_iso_context *base,
			  struct fw_iso_packet *packet,
			  struct fw_iso_buffer *buffer,
			  unsigned long payload)
{
	struct iso_context *ctx = container_of(base, struct iso_context, base);
	unsigned long flags;
	int ret;

	spin_lock_irqsave(&ctx->context.ohci->lock, flags);
	if (base->type == FW_ISO_CONTEXT_TRANSMIT)
		ret = ohci_queue_iso_transmit(base, packet, buffer, payload);
	else
		ret = ohci_queue_iso_receive_packet_per_buffer(base, packet,
							buffer, payload);
	spin_unlock_irqrestore(&ctx->context.ohci->lock, flags);

	return ret;
}

static const struct fw_card_driver ohci_driver = {
	.enable			= ohci_enable,
	.update_phy_reg		= ohci_update_phy_reg,
	.set_config_rom		= ohci_set_config_rom,
	.send_request		= ohci_send_request,
	.send_response		= ohci_send_response,
	.cancel_packet		= ohci_cancel_packet,
	.enable_phys_dma	= ohci_enable_phys_dma,
	.get_cycle_time		= ohci_get_cycle_time,

	.allocate_iso_context	= ohci_allocate_iso_context,
	.free_iso_context	= ohci_free_iso_context,
	.queue_iso		= ohci_queue_iso,
	.start_iso		= ohci_start_iso,
	.stop_iso		= ohci_stop_iso,
};

#ifdef CONFIG_PPC_PMAC
static void ohci_pmac_on(struct pci_dev *dev)
{
	if (machine_is(powermac)) {
		struct device_node *ofn = pci_device_to_OF_node(dev);

		if (ofn) {
			pmac_call_feature(PMAC_FTR_1394_CABLE_POWER, ofn, 0, 1);
			pmac_call_feature(PMAC_FTR_1394_ENABLE, ofn, 0, 1);
		}
	}
}

static void ohci_pmac_off(struct pci_dev *dev)
{
	if (machine_is(powermac)) {
		struct device_node *ofn = pci_device_to_OF_node(dev);

		if (ofn) {
			pmac_call_feature(PMAC_FTR_1394_ENABLE, ofn, 0, 0);
			pmac_call_feature(PMAC_FTR_1394_CABLE_POWER, ofn, 0, 0);
		}
	}
}
#else
#define ohci_pmac_on(dev)
#define ohci_pmac_off(dev)
#endif /* CONFIG_PPC_PMAC */

static int __devinit pci_probe(struct pci_dev *dev,
			       const struct pci_device_id *ent)
{
	struct fw_ohci *ohci;
	u32 bus_options, max_receive, link_speed, version;
	u64 guid;
	int err;
	size_t size;

	ohci = kzalloc(sizeof(*ohci), GFP_KERNEL);
	if (ohci == NULL) {
		err = -ENOMEM;
		goto fail;
	}

	fw_card_initialize(&ohci->card, &ohci_driver, &dev->dev);

	ohci_pmac_on(dev);

	err = pci_enable_device(dev);
	if (err) {
		fw_error("Failed to enable OHCI hardware\n");
		goto fail_free;
	}

	pci_set_master(dev);
	pci_write_config_dword(dev, OHCI1394_PCI_HCI_Control, 0);
	pci_set_drvdata(dev, ohci);

	spin_lock_init(&ohci->lock);

	tasklet_init(&ohci->bus_reset_tasklet,
		     bus_reset_tasklet, (unsigned long)ohci);

	err = pci_request_region(dev, 0, ohci_driver_name);
	if (err) {
		fw_error("MMIO resource unavailable\n");
		goto fail_disable;
	}

	ohci->registers = pci_iomap(dev, 0, OHCI1394_REGISTER_SIZE);
	if (ohci->registers == NULL) {
		fw_error("Failed to remap registers\n");
		err = -ENXIO;
		goto fail_iomem;
	}

	version = reg_read(ohci, OHCI1394_Version) & 0x00ff00ff;

#if defined(CONFIG_PPC_PMAC) && defined(CONFIG_PPC32)
	ohci->old_uninorth = dev->vendor == PCI_VENDOR_ID_APPLE &&
			     dev->device == PCI_DEVICE_ID_APPLE_UNI_N_FW;
#endif
	ohci->bus_reset_packet_quirk = dev->vendor == PCI_VENDOR_ID_TI;

	ohci->iso_cycle_timer_quirk = dev->vendor == PCI_VENDOR_ID_AL	||
				      dev->vendor == PCI_VENDOR_ID_NEC	||
				      dev->vendor == PCI_VENDOR_ID_VIA;

	ar_context_init(&ohci->ar_request_ctx, ohci,
			OHCI1394_AsReqRcvContextControlSet);

	ar_context_init(&ohci->ar_response_ctx, ohci,
			OHCI1394_AsRspRcvContextControlSet);

	context_init(&ohci->at_request_ctx, ohci,
		     OHCI1394_AsReqTrContextControlSet, handle_at_packet);

	context_init(&ohci->at_response_ctx, ohci,
		     OHCI1394_AsRspTrContextControlSet, handle_at_packet);

	reg_write(ohci, OHCI1394_IsoRecvIntMaskSet, ~0);
	ohci->it_context_mask = reg_read(ohci, OHCI1394_IsoRecvIntMaskSet);
	reg_write(ohci, OHCI1394_IsoRecvIntMaskClear, ~0);
	size = sizeof(struct iso_context) * hweight32(ohci->it_context_mask);
	ohci->it_context_list = kzalloc(size, GFP_KERNEL);

	reg_write(ohci, OHCI1394_IsoXmitIntMaskSet, ~0);
	ohci->ir_context_channels = ~0ULL;
	ohci->ir_context_mask = reg_read(ohci, OHCI1394_IsoXmitIntMaskSet);
	reg_write(ohci, OHCI1394_IsoXmitIntMaskClear, ~0);
	size = sizeof(struct iso_context) * hweight32(ohci->ir_context_mask);
	ohci->ir_context_list = kzalloc(size, GFP_KERNEL);

	if (ohci->it_context_list == NULL || ohci->ir_context_list == NULL) {
		err = -ENOMEM;
		goto fail_contexts;
	}

	/* self-id dma buffer allocation */
	ohci->self_id_cpu = dma_alloc_coherent(ohci->card.device,
					       SELF_ID_BUF_SIZE,
					       &ohci->self_id_bus,
					       GFP_KERNEL);
	if (ohci->self_id_cpu == NULL) {
		err = -ENOMEM;
		goto fail_contexts;
	}

	bus_options = reg_read(ohci, OHCI1394_BusOptions);
	max_receive = (bus_options >> 12) & 0xf;
	link_speed = bus_options & 0x7;
	guid = ((u64) reg_read(ohci, OHCI1394_GUIDHi) << 32) |
		reg_read(ohci, OHCI1394_GUIDLo);

	err = fw_card_add(&ohci->card, max_receive, link_speed, guid);
	if (err)
		goto fail_self_id;

	fw_notify("Added fw-ohci device %s, OHCI version %x.%x\n",
		  dev_name(&dev->dev), version >> 16, version & 0xff);

	return 0;

 fail_self_id:
	dma_free_coherent(ohci->card.device, SELF_ID_BUF_SIZE,
			  ohci->self_id_cpu, ohci->self_id_bus);
 fail_contexts:
	kfree(ohci->ir_context_list);
	kfree(ohci->it_context_list);
	context_release(&ohci->at_response_ctx);
	context_release(&ohci->at_request_ctx);
	ar_context_release(&ohci->ar_response_ctx);
	ar_context_release(&ohci->ar_request_ctx);
	pci_iounmap(dev, ohci->registers);
 fail_iomem:
	pci_release_region(dev, 0);
 fail_disable:
	pci_disable_device(dev);
 fail_free:
	kfree(&ohci->card);
	ohci_pmac_off(dev);
 fail:
	if (err == -ENOMEM)
		fw_error("Out of memory\n");

	return err;
}

static void pci_remove(struct pci_dev *dev)
{
	struct fw_ohci *ohci;

	ohci = pci_get_drvdata(dev);
	reg_write(ohci, OHCI1394_IntMaskClear, ~0);
	flush_writes(ohci);
	fw_core_remove_card(&ohci->card);

	/*
	 * FIXME: Fail all pending packets here, now that the upper
	 * layers can't queue any more.
	 */

	software_reset(ohci);
	free_irq(dev->irq, ohci);

	if (ohci->next_config_rom && ohci->next_config_rom != ohci->config_rom)
		dma_free_coherent(ohci->card.device, CONFIG_ROM_SIZE,
				  ohci->next_config_rom, ohci->next_config_rom_bus);
	if (ohci->config_rom)
		dma_free_coherent(ohci->card.device, CONFIG_ROM_SIZE,
				  ohci->config_rom, ohci->config_rom_bus);
	dma_free_coherent(ohci->card.device, SELF_ID_BUF_SIZE,
			  ohci->self_id_cpu, ohci->self_id_bus);
	ar_context_release(&ohci->ar_request_ctx);
	ar_context_release(&ohci->ar_response_ctx);
	context_release(&ohci->at_request_ctx);
	context_release(&ohci->at_response_ctx);
	kfree(ohci->it_context_list);
	kfree(ohci->ir_context_list);
	pci_iounmap(dev, ohci->registers);
	pci_release_region(dev, 0);
	pci_disable_device(dev);
	kfree(&ohci->card);
	ohci_pmac_off(dev);

	fw_notify("Removed fw-ohci device.\n");
}

#ifdef CONFIG_PM
static int pci_suspend(struct pci_dev *dev, pm_message_t state)
{
	struct fw_ohci *ohci = pci_get_drvdata(dev);
	int err;

	software_reset(ohci);
	free_irq(dev->irq, ohci);
	err = pci_save_state(dev);
	if (err) {
		fw_error("pci_save_state failed\n");
		return err;
	}
	err = pci_set_power_state(dev, pci_choose_state(dev, state));
	if (err)
		fw_error("pci_set_power_state failed with %d\n", err);
	ohci_pmac_off(dev);

	return 0;
}

static int pci_resume(struct pci_dev *dev)
{
	struct fw_ohci *ohci = pci_get_drvdata(dev);
	int err;

	ohci_pmac_on(dev);
	pci_set_power_state(dev, PCI_D0);
	pci_restore_state(dev);
	err = pci_enable_device(dev);
	if (err) {
		fw_error("pci_enable_device failed\n");
		return err;
	}

	return ohci_enable(&ohci->card, NULL, 0);
}
#endif

static const struct pci_device_id pci_table[] = {
	{ PCI_DEVICE_CLASS(PCI_CLASS_SERIAL_FIREWIRE_OHCI, ~0) },
	{ }
};

MODULE_DEVICE_TABLE(pci, pci_table);

static struct pci_driver fw_ohci_pci_driver = {
	.name		= ohci_driver_name,
	.id_table	= pci_table,
	.probe		= pci_probe,
	.remove		= pci_remove,
#ifdef CONFIG_PM
	.resume		= pci_resume,
	.suspend	= pci_suspend,
#endif
};

MODULE_AUTHOR("Kristian Hoegsberg <krh@bitplanet.net>");
MODULE_DESCRIPTION("Driver for PCI OHCI IEEE1394 controllers");
MODULE_LICENSE("GPL");

/* Provide a module alias so root-on-sbp2 initrds don't break. */
#ifndef CONFIG_IEEE1394_OHCI1394_MODULE
MODULE_ALIAS("ohci1394");
#endif

static int __init fw_ohci_init(void)
{
	return pci_register_driver(&fw_ohci_pci_driver);
}

static void __exit fw_ohci_cleanup(void)
{
	pci_unregister_driver(&fw_ohci_pci_driver);
}

module_init(fw_ohci_init);
module_exit(fw_ohci_cleanup);