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1/* $Id: head.S,v 1.7 2003/09/01 17:58:19 lethal Exp $
2 *
3 * arch/sh/kernel/head.S
4 *
5 * Copyright (C) 1999, 2000 Niibe Yutaka & Kaz Kojima
3d467676 6 * Copyright (C) 2010 Matt Fleming
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7 *
8 * This file is subject to the terms and conditions of the GNU General Public
9 * License. See the file "COPYING" in the main directory of this archive
10 * for more details.
11 *
12 * Head.S contains the SH exception handlers and startup code.
13 */
bbe215c2 14#include <linux/init.h>
1da177e4 15#include <linux/linkage.h>
d153ea88 16#include <asm/thread_info.h>
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17#include <asm/mmu.h>
18#include <cpu/mmu_context.h>
1da177e4 19
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20#ifdef CONFIG_CPU_SH4A
21#define SYNCO() synco
22
23#define PREFI(label, reg) \
24 mov.l label, reg; \
25 prefi @reg
26#else
27#define SYNCO()
28#define PREFI(label, reg)
29#endif
30
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31 .section .empty_zero_page, "aw"
32ENTRY(empty_zero_page)
33 .long 1 /* MOUNT_ROOT_RDONLY */
34 .long 0 /* RAMDISK_FLAGS */
35 .long 0x0200 /* ORIG_ROOT_DEV */
36 .long 1 /* LOADER_TYPE */
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37 .long 0x00000000 /* INITRD_START */
38 .long 0x00000000 /* INITRD_SIZE */
a0ab3668 39#ifdef CONFIG_32BIT
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40 .long 0x53453f00 + 32 /* "SE?" = 32 bit */
41#else
42 .long 0x53453f00 + 29 /* "SE?" = 29 bit */
43#endif
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441:
45 .skip PAGE_SIZE - empty_zero_page - 1b
1da177e4 46
bbe215c2 47 __HEAD
339547bf 48
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49/*
50 * Condition at the entry of _stext:
51 *
52 * BSC has already been initialized.
53 * INTC may or may not be initialized.
54 * VBR may or may not be initialized.
55 * MMU may or may not be initialized.
56 * Cache may or may not be initialized.
57 * Hardware (including on-chip modules) may or may not be initialized.
58 *
59 */
60ENTRY(_stext)
61 ! Initialize Status Register
62 mov.l 1f, r0 ! MD=1, RB=0, BL=0, IMASK=0xF
63 ldc r0, sr
64 ! Initialize global interrupt mask
de398406 65#ifdef CONFIG_CPU_HAS_SR_RB
aba1030a 66 mov #0, r0
1da177e4 67 ldc r0, r6_bank
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68#endif
69
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70 /*
71 * Prefetch if possible to reduce cache miss penalty.
72 *
73 * We do this early on for SH-4A as a micro-optimization,
74 * as later on we will have speculative execution enabled
75 * and this will become less of an issue.
76 */
77 PREFI(5f, r0)
78 PREFI(6f, r0)
79
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80 !
81 mov.l 2f, r0
82 mov r0, r15 ! Set initial r15 (stack pointer)
de398406 83#ifdef CONFIG_CPU_HAS_SR_RB
aba1030a 84 mov.l 7f, r0
1da177e4 85 ldc r0, r7_bank ! ... and initial thread_info
de398406 86#endif
740a3e67 87
d01447b3 88#ifdef CONFIG_PMB
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89/*
90 * Reconfigure the initial PMB mappings setup by the hardware.
91 *
92 * When we boot in 32-bit MMU mode there are 2 PMB entries already
93 * setup for us.
94 *
95 * Entry VPN PPN V SZ C UB WT
96 * ---------------------------------------------------------------
97 * 0 0x80000000 0x00000000 1 512MB 1 0 1
98 * 1 0xA0000000 0x00000000 1 512MB 0 0 0
99 *
100 * But we reprogram them here because we want complete control over
101 * our address space and the initial mappings may not map PAGE_OFFSET
102 * to __MEMORY_START (or even map all of our RAM).
103 *
104 * Once we've setup cached and uncached mappings we clear the rest of the
105 * PMB entries. This clearing also deals with the fact that PMB entries
106 * can persist across reboots. The PMB could have been left in any state
107 * when the reboot occurred, so to be safe we clear all entries and start
108 * with with a clean slate.
109 *
110 * The uncached mapping is constructed using the smallest possible
111 * mapping with a single unbufferable page. Only the kernel text needs to
112 * be covered via the uncached mapping so that certain functions can be
113 * run uncached.
114 *
115 * Drivers and the like that have previously abused the 1:1 identity
116 * mapping are unsupported in 32-bit mode and must specify their caching
117 * preference when page tables are constructed.
118 *
119 * This frees up the P2 space for more nefarious purposes.
120 *
121 * Register utilization is as follows:
122 *
123 * r0 = PMB_DATA data field
124 * r1 = PMB_DATA address field
125 * r2 = PMB_ADDR data field
126 * r3 = PMB_ADDR address field
127 * r4 = PMB_E_SHIFT
128 * r5 = remaining amount of RAM to map
129 * r6 = PMB mapping size we're trying to use
130 * r7 = cached_to_uncached
131 * r8 = scratch register
132 * r9 = scratch register
133 * r10 = number of PMB entries we've setup
035ca59f 134 * r11 = scratch register
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135 */
136
137 mov.l .LMMUCR, r1 /* Flush the TLB */
138 mov.l @r1, r0
139 or #MMUCR_TI, r0
140 mov.l r0, @r1
141
142 mov.l .LMEMORY_SIZE, r5
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143
144 mov #PMB_E_SHIFT, r0
145 mov #0x1, r4
146 shld r0, r4
77c2019f 147
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148 mov.l .LFIRST_DATA_ENTRY, r0
149 mov.l .LPMB_DATA, r1
150 mov.l .LFIRST_ADDR_ENTRY, r2
151 mov.l .LPMB_ADDR, r3
152
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153 /*
154 * First we need to walk the PMB and figure out if there are any
155 * existing mappings that match the initial mappings VPN/PPN.
156 * If these have already been established by the bootloader, we
157 * don't bother setting up new entries here, and let the late PMB
158 * initialization take care of things instead.
159 *
160 * Note that we may need to coalesce and merge entries in order
161 * to reclaim more available PMB slots, which is much more than
162 * we want to do at this early stage.
163 */
164 mov #0, r10
165 mov #NR_PMB_ENTRIES, r9
166
167 mov r1, r7 /* temporary PMB_DATA iter */
168
169.Lvalidate_existing_mappings:
170
035ca59f 171 mov.l .LPMB_DATA_MASK, r11
d01447b3 172 mov.l @r7, r8
035ca59f 173 and r11, r8
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174 cmp/eq r0, r8 /* Check for valid __MEMORY_START mappings */
175 bt .Lpmb_done
176
177 add #1, r10 /* Increment the loop counter */
178 cmp/eq r9, r10
179 bf/s .Lvalidate_existing_mappings
180 add r4, r7 /* Increment to the next PMB_DATA entry */
181
182 /*
183 * If we've fallen through, continue with setting up the initial
184 * mappings.
185 */
186
187 mov r5, r7 /* cached_to_uncached */
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188 mov #0, r10
189
9edef286 190#ifdef CONFIG_UNCACHED_MAPPING
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191 /*
192 * Uncached mapping
193 */
194 mov #(PMB_SZ_16M >> 2), r9
195 shll2 r9
196
197 mov #(PMB_UB >> 8), r8
198 shll8 r8
199
200 or r0, r8
201 or r9, r8
202 mov.l r8, @r1
203 mov r2, r8
204 add r7, r8
205 mov.l r8, @r3
206
207 add r4, r1
208 add r4, r3
209 add #1, r10
9edef286 210#endif
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211
212/*
213 * Iterate over all of the available sizes from largest to
214 * smallest for constructing the cached mapping.
215 */
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216#define __PMB_ITER_BY_SIZE(size) \
217.L##size: \
218 mov #(size >> 4), r6; \
219 shll16 r6; \
220 shll8 r6; \
221 \
222 cmp/hi r5, r6; \
223 bt 9999f; \
224 \
225 mov #(PMB_SZ_##size##M >> 2), r9; \
226 shll2 r9; \
227 \
228 /* \
229 * Cached mapping \
230 */ \
231 mov #PMB_C, r8; \
232 or r0, r8; \
233 or r9, r8; \
234 mov.l r8, @r1; \
235 mov.l r2, @r3; \
236 \
237 /* Increment to the next PMB_DATA entry */ \
238 add r4, r1; \
239 /* Increment to the next PMB_ADDR entry */ \
240 add r4, r3; \
241 /* Increment number of PMB entries */ \
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242 add #1, r10; \
243 \
244 sub r6, r5; \
245 add r6, r0; \
246 add r6, r2; \
247 \
248 bra .L##size; \
2499999:
250
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251 __PMB_ITER_BY_SIZE(512)
252 __PMB_ITER_BY_SIZE(128)
253 __PMB_ITER_BY_SIZE(64)
254 __PMB_ITER_BY_SIZE(16)
3d467676 255
9edef286 256#ifdef CONFIG_UNCACHED_MAPPING
2023b843 257 /*
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258 * Now that we can access it, update cached_to_uncached and
259 * uncached_size.
2023b843 260 */
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261 mov.l .Lcached_to_uncached, r0
262 mov.l r7, @r0
263
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264 mov.l .Luncached_size, r0
265 mov #1, r7
266 shll16 r7
267 shll8 r7
268 mov.l r7, @r0
9edef286 269#endif
3125ee72 270
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271 /*
272 * Clear the remaining PMB entries.
273 *
274 * r3 = entry to begin clearing from
275 * r10 = number of entries we've setup so far
276 */
277 mov #0, r1
51becfd9 278 mov #NR_PMB_ENTRIES, r0
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279
280.Lagain:
281 mov.l r1, @r3 /* Clear PMB_ADDR entry */
282 add #1, r10 /* Increment the loop counter */
283 cmp/eq r0, r10
284 bf/s .Lagain
285 add r4, r3 /* Increment to the next PMB_ADDR entry */
286
287 mov.l 6f, r0
288 icbi @r0
289
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290.Lpmb_done:
291#endif /* CONFIG_PMB */
3d467676 292
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293#ifndef CONFIG_SH_NO_BSS_INIT
294 /*
295 * Don't clear BSS if running on slow platforms such as an RTL simulation,
296 * remote memory via SHdebug link, etc. For these the memory can be guaranteed
297 * to be all zero on boot anyway.
298 */
299 ! Clear BSS area
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300#ifdef CONFIG_SMP
301 mov.l 3f, r0
302 cmp/eq #0, r0 ! skip clear if set to zero
303 bt 10f
304#endif
305
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306 mov.l 3f, r1
307 add #4, r1
308 mov.l 4f, r2
309 mov #0, r0
3109: cmp/hs r2, r1
311 bf/s 9b ! while (r1 < r2)
312 mov.l r0,@-r2
b7e108ee 313
aba1030a 31410:
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315#endif
316
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317 ! Additional CPU initialization
318 mov.l 6f, r0
319 jsr @r0
320 nop
321
322 SYNCO() ! Wait for pending instructions..
aba1030a 323
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324 ! Start kernel
325 mov.l 5f, r0
326 jmp @r0
327 nop
328
329 .balign 4
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330#if defined(CONFIG_CPU_SH2)
3311: .long 0x000000F0 ! IMASK=0xF
332#else
68a1aed7 3331: .long 0x500080F0 ! MD=1, RB=0, BL=1, FD=1, IMASK=0xF
de398406 334#endif
aba1030a 335ENTRY(stack_start)
d153ea88 3362: .long init_thread_union+THREAD_SIZE
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3373: .long __bss_start
3384: .long _end
3395: .long start_kernel
4a6feab0 3406: .long cpu_init
aba1030a 3417: .long init_thread_union
3d467676 342
d01447b3 343#ifdef CONFIG_PMB
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344.LPMB_ADDR: .long PMB_ADDR
345.LPMB_DATA: .long PMB_DATA
035ca59f 346.LPMB_DATA_MASK: .long PMB_PFN_MASK | PMB_V
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347.LFIRST_ADDR_ENTRY: .long PAGE_OFFSET | PMB_V
348.LFIRST_DATA_ENTRY: .long __MEMORY_START | PMB_V
349.LMMUCR: .long MMUCR
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350.LMEMORY_SIZE: .long __MEMORY_SIZE
351#ifdef CONFIG_UNCACHED_MAPPING
3d467676 352.Lcached_to_uncached: .long cached_to_uncached
3125ee72 353.Luncached_size: .long uncached_size
9edef286 354#endif
3d467676 355#endif