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1/* SPDX-License-Identifier: GPL-2.0
2 * $Id: head.S,v 1.7 2003/09/01 17:58:19 lethal Exp $
3 *
4 * arch/sh/kernel/head.S
5 *
6 * Copyright (C) 1999, 2000 Niibe Yutaka & Kaz Kojima
7 * Copyright (C) 2010 Matt Fleming
8 *
9 * Head.S contains the SH exception handlers and startup code.
10 */
11#include <linux/init.h>
12#include <linux/linkage.h>
13#include <asm/thread_info.h>
14#include <asm/mmu.h>
15#include <cpu/mmu_context.h>
16
17#ifdef CONFIG_CPU_SH4A
18#define SYNCO() synco
19
20#define PREFI(label, reg) \
21 mov.l label, reg; \
22 prefi @reg
23#else
24#define SYNCO()
25#define PREFI(label, reg)
26#endif
27
28 .section .empty_zero_page, "aw"
29ENTRY(empty_zero_page)
30 .long 1 /* MOUNT_ROOT_RDONLY */
31 .long 0 /* RAMDISK_FLAGS */
32 .long 0x0200 /* ORIG_ROOT_DEV */
33 .long 1 /* LOADER_TYPE */
34 .long 0x00000000 /* INITRD_START */
35 .long 0x00000000 /* INITRD_SIZE */
36#ifdef CONFIG_32BIT
37 .long 0x53453f00 + 32 /* "SE?" = 32 bit */
38#else
39 .long 0x53453f00 + 29 /* "SE?" = 29 bit */
40#endif
411:
42 .skip PAGE_SIZE - empty_zero_page - 1b
43
44 __HEAD
45
46/*
47 * Condition at the entry of _stext:
48 *
49 * BSC has already been initialized.
50 * INTC may or may not be initialized.
51 * VBR may or may not be initialized.
52 * MMU may or may not be initialized.
53 * Cache may or may not be initialized.
54 * Hardware (including on-chip modules) may or may not be initialized.
55 *
56 */
57ENTRY(_stext)
58 ! Initialize Status Register
59 mov.l 1f, r0 ! MD=1, RB=0, BL=0, IMASK=0xF
60 ldc r0, sr
61 ! Initialize global interrupt mask
62#ifdef CONFIG_CPU_HAS_SR_RB
63 mov #0, r0
64 ldc r0, r6_bank
65#endif
66
67#ifdef CONFIG_OF_FLATTREE
68 mov r4, r12 ! Store device tree blob pointer in r12
69#endif
70
71 /*
72 * Prefetch if possible to reduce cache miss penalty.
73 *
74 * We do this early on for SH-4A as a micro-optimization,
75 * as later on we will have speculative execution enabled
76 * and this will become less of an issue.
77 */
78 PREFI(5f, r0)
79 PREFI(6f, r0)
80
81 !
82 mov.l 2f, r0
83 mov r0, r15 ! Set initial r15 (stack pointer)
84#ifdef CONFIG_CPU_HAS_SR_RB
85 mov.l 7f, r0
86 ldc r0, r7_bank ! ... and initial thread_info
87#endif
88
89#ifdef CONFIG_PMB
90/*
91 * Reconfigure the initial PMB mappings setup by the hardware.
92 *
93 * When we boot in 32-bit MMU mode there are 2 PMB entries already
94 * setup for us.
95 *
96 * Entry VPN PPN V SZ C UB WT
97 * ---------------------------------------------------------------
98 * 0 0x80000000 0x00000000 1 512MB 1 0 1
99 * 1 0xA0000000 0x00000000 1 512MB 0 0 0
100 *
101 * But we reprogram them here because we want complete control over
102 * our address space and the initial mappings may not map PAGE_OFFSET
103 * to __MEMORY_START (or even map all of our RAM).
104 *
105 * Once we've setup cached and uncached mappings we clear the rest of the
106 * PMB entries. This clearing also deals with the fact that PMB entries
107 * can persist across reboots. The PMB could have been left in any state
108 * when the reboot occurred, so to be safe we clear all entries and start
109 * with with a clean slate.
110 *
111 * The uncached mapping is constructed using the smallest possible
112 * mapping with a single unbufferable page. Only the kernel text needs to
113 * be covered via the uncached mapping so that certain functions can be
114 * run uncached.
115 *
116 * Drivers and the like that have previously abused the 1:1 identity
117 * mapping are unsupported in 32-bit mode and must specify their caching
118 * preference when page tables are constructed.
119 *
120 * This frees up the P2 space for more nefarious purposes.
121 *
122 * Register utilization is as follows:
123 *
124 * r0 = PMB_DATA data field
125 * r1 = PMB_DATA address field
126 * r2 = PMB_ADDR data field
127 * r3 = PMB_ADDR address field
128 * r4 = PMB_E_SHIFT
129 * r5 = remaining amount of RAM to map
130 * r6 = PMB mapping size we're trying to use
131 * r7 = cached_to_uncached
132 * r8 = scratch register
133 * r9 = scratch register
134 * r10 = number of PMB entries we've setup
135 * r11 = scratch register
136 */
137
138 mov.l .LMMUCR, r1 /* Flush the TLB */
139 mov.l @r1, r0
140 or #MMUCR_TI, r0
141 mov.l r0, @r1
142
143 mov.l .LMEMORY_SIZE, r5
144
145 mov #PMB_E_SHIFT, r0
146 mov #0x1, r4
147 shld r0, r4
148
149 mov.l .LFIRST_DATA_ENTRY, r0
150 mov.l .LPMB_DATA, r1
151 mov.l .LFIRST_ADDR_ENTRY, r2
152 mov.l .LPMB_ADDR, r3
153
154 /*
155 * First we need to walk the PMB and figure out if there are any
156 * existing mappings that match the initial mappings VPN/PPN.
157 * If these have already been established by the bootloader, we
158 * don't bother setting up new entries here, and let the late PMB
159 * initialization take care of things instead.
160 *
161 * Note that we may need to coalesce and merge entries in order
162 * to reclaim more available PMB slots, which is much more than
163 * we want to do at this early stage.
164 */
165 mov #0, r10
166 mov #NR_PMB_ENTRIES, r9
167
168 mov r1, r7 /* temporary PMB_DATA iter */
169
170.Lvalidate_existing_mappings:
171
172 mov.l .LPMB_DATA_MASK, r11
173 mov.l @r7, r8
174 and r11, r8
175 cmp/eq r0, r8 /* Check for valid __MEMORY_START mappings */
176 bt .Lpmb_done
177
178 add #1, r10 /* Increment the loop counter */
179 cmp/eq r9, r10
180 bf/s .Lvalidate_existing_mappings
181 add r4, r7 /* Increment to the next PMB_DATA entry */
182
183 /*
184 * If we've fallen through, continue with setting up the initial
185 * mappings.
186 */
187
188 mov r5, r7 /* cached_to_uncached */
189 mov #0, r10
190
191#ifdef CONFIG_UNCACHED_MAPPING
192 /*
193 * Uncached mapping
194 */
195 mov #(PMB_SZ_16M >> 2), r9
196 shll2 r9
197
198 mov #(PMB_UB >> 8), r8
199 shll8 r8
200
201 or r0, r8
202 or r9, r8
203 mov.l r8, @r1
204 mov r2, r8
205 add r7, r8
206 mov.l r8, @r3
207
208 add r4, r1
209 add r4, r3
210 add #1, r10
211#endif
212
213/*
214 * Iterate over all of the available sizes from largest to
215 * smallest for constructing the cached mapping.
216 */
217#define __PMB_ITER_BY_SIZE(size) \
218.L##size: \
219 mov #(size >> 4), r6; \
220 shll16 r6; \
221 shll8 r6; \
222 \
223 cmp/hi r5, r6; \
224 bt 9999f; \
225 \
226 mov #(PMB_SZ_##size##M >> 2), r9; \
227 shll2 r9; \
228 \
229 /* \
230 * Cached mapping \
231 */ \
232 mov #PMB_C, r8; \
233 or r0, r8; \
234 or r9, r8; \
235 mov.l r8, @r1; \
236 mov.l r2, @r3; \
237 \
238 /* Increment to the next PMB_DATA entry */ \
239 add r4, r1; \
240 /* Increment to the next PMB_ADDR entry */ \
241 add r4, r3; \
242 /* Increment number of PMB entries */ \
243 add #1, r10; \
244 \
245 sub r6, r5; \
246 add r6, r0; \
247 add r6, r2; \
248 \
249 bra .L##size; \
2509999:
251
252 __PMB_ITER_BY_SIZE(512)
253 __PMB_ITER_BY_SIZE(128)
254 __PMB_ITER_BY_SIZE(64)
255 __PMB_ITER_BY_SIZE(16)
256
257#ifdef CONFIG_UNCACHED_MAPPING
258 /*
259 * Now that we can access it, update cached_to_uncached and
260 * uncached_size.
261 */
262 mov.l .Lcached_to_uncached, r0
263 mov.l r7, @r0
264
265 mov.l .Luncached_size, r0
266 mov #1, r7
267 shll16 r7
268 shll8 r7
269 mov.l r7, @r0
270#endif
271
272 /*
273 * Clear the remaining PMB entries.
274 *
275 * r3 = entry to begin clearing from
276 * r10 = number of entries we've setup so far
277 */
278 mov #0, r1
279 mov #NR_PMB_ENTRIES, r0
280
281.Lagain:
282 mov.l r1, @r3 /* Clear PMB_ADDR entry */
283 add #1, r10 /* Increment the loop counter */
284 cmp/eq r0, r10
285 bf/s .Lagain
286 add r4, r3 /* Increment to the next PMB_ADDR entry */
287
288 mov.l 6f, r0
289 icbi @r0
290
291.Lpmb_done:
292#endif /* CONFIG_PMB */
293
294#ifndef CONFIG_SH_NO_BSS_INIT
295 /*
296 * Don't clear BSS if running on slow platforms such as an RTL simulation,
297 * remote memory via SHdebug link, etc. For these the memory can be guaranteed
298 * to be all zero on boot anyway.
299 */
300 ! Clear BSS area
301#ifdef CONFIG_SMP
302 mov.l 3f, r0
303 cmp/eq #0, r0 ! skip clear if set to zero
304 bt 10f
305#endif
306
307 mov.l 3f, r1
308 add #4, r1
309 mov.l 4f, r2
310 mov #0, r0
3119: cmp/hs r2, r1
312 bf/s 9b ! while (r1 < r2)
313 mov.l r0,@-r2
314
31510:
316#endif
317
318#ifdef CONFIG_OF_FLATTREE
319 mov.l 8f, r0 ! Make flat device tree available early.
320 jsr @r0
321 mov r12, r4
322#endif
323
324 ! Additional CPU initialization
325 mov.l 6f, r0
326 jsr @r0
327 nop
328
329 SYNCO() ! Wait for pending instructions..
330
331 ! Start kernel
332 mov.l 5f, r0
333 jmp @r0
334 nop
335
336 .balign 4
337#if defined(CONFIG_CPU_SH2)
3381: .long 0x000000F0 ! IMASK=0xF
339#else
3401: .long 0x500080F0 ! MD=1, RB=0, BL=1, FD=1, IMASK=0xF
341#endif
342ENTRY(stack_start)
3432: .long init_thread_union+THREAD_SIZE
3443: .long __bss_start
3454: .long _end
3465: .long start_kernel
3476: .long cpu_init
3487: .long init_thread_union
349#if defined(CONFIG_OF_FLATTREE)
3508: .long sh_fdt_init
351#endif
352
353#ifdef CONFIG_PMB
354.LPMB_ADDR: .long PMB_ADDR
355.LPMB_DATA: .long PMB_DATA
356.LPMB_DATA_MASK: .long PMB_PFN_MASK | PMB_V
357.LFIRST_ADDR_ENTRY: .long PAGE_OFFSET | PMB_V
358.LFIRST_DATA_ENTRY: .long __MEMORY_START | PMB_V
359.LMMUCR: .long MMUCR
360.LMEMORY_SIZE: .long __MEMORY_SIZE
361#ifdef CONFIG_UNCACHED_MAPPING
362.Lcached_to_uncached: .long cached_to_uncached
363.Luncached_size: .long uncached_size
364#endif
365#endif
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
6 * Copyright (C) 2010 Matt Fleming
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 */
14#include <linux/init.h>
15#include <linux/linkage.h>
16#include <asm/thread_info.h>
17#include <asm/mmu.h>
18#include <cpu/mmu_context.h>
19
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
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 */
37 .long 0x00000000 /* INITRD_START */
38 .long 0x00000000 /* INITRD_SIZE */
39#ifdef CONFIG_32BIT
40 .long 0x53453f00 + 32 /* "SE?" = 32 bit */
41#else
42 .long 0x53453f00 + 29 /* "SE?" = 29 bit */
43#endif
441:
45 .skip PAGE_SIZE - empty_zero_page - 1b
46
47 __HEAD
48
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
65#ifdef CONFIG_CPU_HAS_SR_RB
66 mov #0, r0
67 ldc r0, r6_bank
68#endif
69
70#ifdef CONFIG_OF
71 mov r4, r12 ! Store device tree blob pointer in r12
72#endif
73
74 /*
75 * Prefetch if possible to reduce cache miss penalty.
76 *
77 * We do this early on for SH-4A as a micro-optimization,
78 * as later on we will have speculative execution enabled
79 * and this will become less of an issue.
80 */
81 PREFI(5f, r0)
82 PREFI(6f, r0)
83
84 !
85 mov.l 2f, r0
86 mov r0, r15 ! Set initial r15 (stack pointer)
87#ifdef CONFIG_CPU_HAS_SR_RB
88 mov.l 7f, r0
89 ldc r0, r7_bank ! ... and initial thread_info
90#endif
91
92#ifdef CONFIG_PMB
93/*
94 * Reconfigure the initial PMB mappings setup by the hardware.
95 *
96 * When we boot in 32-bit MMU mode there are 2 PMB entries already
97 * setup for us.
98 *
99 * Entry VPN PPN V SZ C UB WT
100 * ---------------------------------------------------------------
101 * 0 0x80000000 0x00000000 1 512MB 1 0 1
102 * 1 0xA0000000 0x00000000 1 512MB 0 0 0
103 *
104 * But we reprogram them here because we want complete control over
105 * our address space and the initial mappings may not map PAGE_OFFSET
106 * to __MEMORY_START (or even map all of our RAM).
107 *
108 * Once we've setup cached and uncached mappings we clear the rest of the
109 * PMB entries. This clearing also deals with the fact that PMB entries
110 * can persist across reboots. The PMB could have been left in any state
111 * when the reboot occurred, so to be safe we clear all entries and start
112 * with with a clean slate.
113 *
114 * The uncached mapping is constructed using the smallest possible
115 * mapping with a single unbufferable page. Only the kernel text needs to
116 * be covered via the uncached mapping so that certain functions can be
117 * run uncached.
118 *
119 * Drivers and the like that have previously abused the 1:1 identity
120 * mapping are unsupported in 32-bit mode and must specify their caching
121 * preference when page tables are constructed.
122 *
123 * This frees up the P2 space for more nefarious purposes.
124 *
125 * Register utilization is as follows:
126 *
127 * r0 = PMB_DATA data field
128 * r1 = PMB_DATA address field
129 * r2 = PMB_ADDR data field
130 * r3 = PMB_ADDR address field
131 * r4 = PMB_E_SHIFT
132 * r5 = remaining amount of RAM to map
133 * r6 = PMB mapping size we're trying to use
134 * r7 = cached_to_uncached
135 * r8 = scratch register
136 * r9 = scratch register
137 * r10 = number of PMB entries we've setup
138 * r11 = scratch register
139 */
140
141 mov.l .LMMUCR, r1 /* Flush the TLB */
142 mov.l @r1, r0
143 or #MMUCR_TI, r0
144 mov.l r0, @r1
145
146 mov.l .LMEMORY_SIZE, r5
147
148 mov #PMB_E_SHIFT, r0
149 mov #0x1, r4
150 shld r0, r4
151
152 mov.l .LFIRST_DATA_ENTRY, r0
153 mov.l .LPMB_DATA, r1
154 mov.l .LFIRST_ADDR_ENTRY, r2
155 mov.l .LPMB_ADDR, r3
156
157 /*
158 * First we need to walk the PMB and figure out if there are any
159 * existing mappings that match the initial mappings VPN/PPN.
160 * If these have already been established by the bootloader, we
161 * don't bother setting up new entries here, and let the late PMB
162 * initialization take care of things instead.
163 *
164 * Note that we may need to coalesce and merge entries in order
165 * to reclaim more available PMB slots, which is much more than
166 * we want to do at this early stage.
167 */
168 mov #0, r10
169 mov #NR_PMB_ENTRIES, r9
170
171 mov r1, r7 /* temporary PMB_DATA iter */
172
173.Lvalidate_existing_mappings:
174
175 mov.l .LPMB_DATA_MASK, r11
176 mov.l @r7, r8
177 and r11, r8
178 cmp/eq r0, r8 /* Check for valid __MEMORY_START mappings */
179 bt .Lpmb_done
180
181 add #1, r10 /* Increment the loop counter */
182 cmp/eq r9, r10
183 bf/s .Lvalidate_existing_mappings
184 add r4, r7 /* Increment to the next PMB_DATA entry */
185
186 /*
187 * If we've fallen through, continue with setting up the initial
188 * mappings.
189 */
190
191 mov r5, r7 /* cached_to_uncached */
192 mov #0, r10
193
194#ifdef CONFIG_UNCACHED_MAPPING
195 /*
196 * Uncached mapping
197 */
198 mov #(PMB_SZ_16M >> 2), r9
199 shll2 r9
200
201 mov #(PMB_UB >> 8), r8
202 shll8 r8
203
204 or r0, r8
205 or r9, r8
206 mov.l r8, @r1
207 mov r2, r8
208 add r7, r8
209 mov.l r8, @r3
210
211 add r4, r1
212 add r4, r3
213 add #1, r10
214#endif
215
216/*
217 * Iterate over all of the available sizes from largest to
218 * smallest for constructing the cached mapping.
219 */
220#define __PMB_ITER_BY_SIZE(size) \
221.L##size: \
222 mov #(size >> 4), r6; \
223 shll16 r6; \
224 shll8 r6; \
225 \
226 cmp/hi r5, r6; \
227 bt 9999f; \
228 \
229 mov #(PMB_SZ_##size##M >> 2), r9; \
230 shll2 r9; \
231 \
232 /* \
233 * Cached mapping \
234 */ \
235 mov #PMB_C, r8; \
236 or r0, r8; \
237 or r9, r8; \
238 mov.l r8, @r1; \
239 mov.l r2, @r3; \
240 \
241 /* Increment to the next PMB_DATA entry */ \
242 add r4, r1; \
243 /* Increment to the next PMB_ADDR entry */ \
244 add r4, r3; \
245 /* Increment number of PMB entries */ \
246 add #1, r10; \
247 \
248 sub r6, r5; \
249 add r6, r0; \
250 add r6, r2; \
251 \
252 bra .L##size; \
2539999:
254
255 __PMB_ITER_BY_SIZE(512)
256 __PMB_ITER_BY_SIZE(128)
257 __PMB_ITER_BY_SIZE(64)
258 __PMB_ITER_BY_SIZE(16)
259
260#ifdef CONFIG_UNCACHED_MAPPING
261 /*
262 * Now that we can access it, update cached_to_uncached and
263 * uncached_size.
264 */
265 mov.l .Lcached_to_uncached, r0
266 mov.l r7, @r0
267
268 mov.l .Luncached_size, r0
269 mov #1, r7
270 shll16 r7
271 shll8 r7
272 mov.l r7, @r0
273#endif
274
275 /*
276 * Clear the remaining PMB entries.
277 *
278 * r3 = entry to begin clearing from
279 * r10 = number of entries we've setup so far
280 */
281 mov #0, r1
282 mov #NR_PMB_ENTRIES, r0
283
284.Lagain:
285 mov.l r1, @r3 /* Clear PMB_ADDR entry */
286 add #1, r10 /* Increment the loop counter */
287 cmp/eq r0, r10
288 bf/s .Lagain
289 add r4, r3 /* Increment to the next PMB_ADDR entry */
290
291 mov.l 6f, r0
292 icbi @r0
293
294.Lpmb_done:
295#endif /* CONFIG_PMB */
296
297#ifndef CONFIG_SH_NO_BSS_INIT
298 /*
299 * Don't clear BSS if running on slow platforms such as an RTL simulation,
300 * remote memory via SHdebug link, etc. For these the memory can be guaranteed
301 * to be all zero on boot anyway.
302 */
303 ! Clear BSS area
304#ifdef CONFIG_SMP
305 mov.l 3f, r0
306 cmp/eq #0, r0 ! skip clear if set to zero
307 bt 10f
308#endif
309
310 mov.l 3f, r1
311 add #4, r1
312 mov.l 4f, r2
313 mov #0, r0
3149: cmp/hs r2, r1
315 bf/s 9b ! while (r1 < r2)
316 mov.l r0,@-r2
317
31810:
319#endif
320
321#ifdef CONFIG_OF
322 mov.l 8f, r0 ! Make flat device tree available early.
323 jsr @r0
324 mov r12, r4
325#endif
326
327 ! Additional CPU initialization
328 mov.l 6f, r0
329 jsr @r0
330 nop
331
332 SYNCO() ! Wait for pending instructions..
333
334 ! Start kernel
335 mov.l 5f, r0
336 jmp @r0
337 nop
338
339 .balign 4
340#if defined(CONFIG_CPU_SH2)
3411: .long 0x000000F0 ! IMASK=0xF
342#else
3431: .long 0x500080F0 ! MD=1, RB=0, BL=1, FD=1, IMASK=0xF
344#endif
345ENTRY(stack_start)
3462: .long init_thread_union+THREAD_SIZE
3473: .long __bss_start
3484: .long _end
3495: .long start_kernel
3506: .long cpu_init
3517: .long init_thread_union
352#if defined(CONFIG_OF)
3538: .long sh_fdt_init
354#endif
355
356#ifdef CONFIG_PMB
357.LPMB_ADDR: .long PMB_ADDR
358.LPMB_DATA: .long PMB_DATA
359.LPMB_DATA_MASK: .long PMB_PFN_MASK | PMB_V
360.LFIRST_ADDR_ENTRY: .long PAGE_OFFSET | PMB_V
361.LFIRST_DATA_ENTRY: .long __MEMORY_START | PMB_V
362.LMMUCR: .long MMUCR
363.LMEMORY_SIZE: .long __MEMORY_SIZE
364#ifdef CONFIG_UNCACHED_MAPPING
365.Lcached_to_uncached: .long cached_to_uncached
366.Luncached_size: .long uncached_size
367#endif
368#endif