git://bbs.cooldavid.org / net-next-2.6.git / blame
| Commit | Line | Data |
|---|---|---|
| 1da177e4 LT |
1 | /* |
| 2 | * linux/arch/arm/mach-footbridge/isa-timer.c | |
| 3 | * | |
| 4 | * Copyright (C) 1998 Russell King. | |
| 5 | * Copyright (C) 1998 Phil Blundell | |
| 6 | */ | |
| 7 | #include <linux/init.h> | |
| 8 | #include <linux/interrupt.h> | |
| 55e86989 | 9 | #include <linux/irq.h> |
| 1da177e4 LT |
10 | |
| 11 | #include <asm/io.h> | |
| 12 | #include <asm/irq.h> | |
| 13 | ||
| 14 | #include <asm/mach/time.h> | |
| 15 | ||
| 16 | #include "common.h" | |
| 17 | ||
| 18 | /* | |
| 19 | * ISA timer tick support | |
| 20 | */ | |
| 21 | #define mSEC_10_from_14 ((14318180 + 100) / 200) | |
| 22 | ||
| 23 | static unsigned long isa_gettimeoffset(void) | |
| 24 | { | |
| 25 | int count; | |
| 26 | ||
| 27 | static int count_p = (mSEC_10_from_14/6); /* for the first call after boot */ | |
| 28 | static unsigned long jiffies_p = 0; | |
| 29 | ||
| 30 | /* | |
| 31 | * cache volatile jiffies temporarily; we have IRQs turned off. | |
| 32 | */ | |
| 33 | unsigned long jiffies_t; | |
| 34 | ||
| 35 | /* timer count may underflow right here */ | |
| 36 | outb_p(0x00, 0x43); /* latch the count ASAP */ | |
| 37 | ||
| 38 | count = inb_p(0x40); /* read the latched count */ | |
| 39 | ||
| 40 | /* | |
| 41 | * We do this guaranteed double memory access instead of a _p | |
| 42 | * postfix in the previous port access. Wheee, hackady hack | |
| 43 | */ | |
| 44 | jiffies_t = jiffies; | |
| 45 | ||
| 46 | count |= inb_p(0x40) << 8; | |
| 47 | ||
| 48 | /* Detect timer underflows. If we haven't had a timer tick since | |
| 49 | the last time we were called, and time is apparently going | |
| 50 | backwards, the counter must have wrapped during this routine. */ | |
| 51 | if ((jiffies_t == jiffies_p) && (count > count_p)) | |
| 52 | count -= (mSEC_10_from_14/6); | |
| 53 | else | |
| 54 | jiffies_p = jiffies_t; | |
| 55 | ||
| 56 | count_p = count; | |
| 57 | ||
| 58 | count = (((mSEC_10_from_14/6)-1) - count) * (tick_nsec / 1000); | |
| 59 | count = (count + (mSEC_10_from_14/6)/2) / (mSEC_10_from_14/6); | |
| 60 | ||
| 61 | return count; | |
| 62 | } | |
| 63 | ||
| 64 | static irqreturn_t | |
| 0cd61b68 | 65 | isa_timer_interrupt(int irq, void *dev_id) |
| 1da177e4 LT |
66 | { |
| 67 | write_seqlock(&xtime_lock); | |
| 0cd61b68 | 68 | timer_tick(); |
| 1da177e4 LT |
69 | write_sequnlock(&xtime_lock); |
| 70 | return IRQ_HANDLED; | |
| 71 | } | |
| 72 | ||
| 73 | static struct irqaction isa_timer_irq = { | |
| 74 | .name = "ISA timer tick", | |
| 75 | .handler = isa_timer_interrupt, | |
| b30fabad | 76 | .flags = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL, |
| 1da177e4 LT |
77 | }; |
| 78 | ||
| 79 | static void __init isa_timer_init(void) | |
| 80 | { | |
| 81 | isa_rtc_init(); | |
| 82 | ||
| 83 | /* enable PIT timer */ | |
| 84 | /* set for periodic (4) and LSB/MSB write (0x30) */ | |
| 85 | outb(0x34, 0x43); | |
| 86 | outb((mSEC_10_from_14/6) & 0xFF, 0x40); | |
| 87 | outb((mSEC_10_from_14/6) >> 8, 0x40); | |
| 88 | ||
| 89 | setup_irq(IRQ_ISA_TIMER, &isa_timer_irq); | |
| 90 | } | |
| 91 | ||
| 92 | struct sys_timer isa_timer = { | |
| 93 | .init = isa_timer_init, | |
| 94 | .offset = isa_gettimeoffset, | |
| 95 | }; |