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*/
1 /*
2 * arch/mips/kernel/head.S
3 *
4 * Copyright (C) 1994, 1995 Waldorf Electronics
5 * Written by Ralf Baechle and Andreas Busse
6 *
7 * Head.S contains the MIPS exception handler and startup code.
8 */
9 #include <linux/tasks.h>
10
11 #include <asm/asm.h>
12 #include <asm/segment.h>
13 #include <asm/cachectl.h>
14 #include <asm/mipsregs.h>
15 #include <asm/mipsconfig.h>
16 #include <asm/stackframe.h>
17 #include <asm/bootinfo.h>
18
19 #define PAGE_SIZE 0x1000
20
21 #define MODE_GLOBAL 0x0001 /* shared for all processes */
22 #define MODE_ALIAS 0x0016 /* uncachable */
23
24 .text
25 .set mips3
26 /*
27 * This is space for the interrupt handlers.
28 * They are located at virtual address KSEG[01] (physical 0x0)
29 */
30 /*
31 * TLB refill, EXL == 0
32 */
33 .set noreorder
34 .set noat
35 LEAF(except_vec0)
36 dmfc0 k1,CP0_CONTEXT
37 dsra k1,1
38 lwu k0,(k1) # May cause another exception
39 lwu k1,4(k1)
40 dsrl k0,6 # Convert to EntryLo format
41 dsrl k1,6 # Convert to EntryLo format
42 dmtc0 k0,CP0_ENTRYLO0
43 dmtc0 k1,CP0_ENTRYLO1
44 nop # Needed for R4[04]00 pipeline
45 tlbwr
46 nop # Needed for R4[04]00 pipeline
47 nop
48 nop
49 eret
50 /*
51 * Workaround for R4000 bug. For explanation see MIPS
52 * docs. Note that this is so obscure that it will almost
53 * never happen. Well, but Mips writes about its bugs.
54 */
55 nop
56 eret
57 END(except_vec0)
58
59 /*
60 * XTLB refill, EXL == 0
61 * Should never be reached
62 */
63 .org except_vec0+0x80
64 LEAF(except_vec1)
65 PANIC("XTLB Refill exception.\n")
66 1: j 1b
67 nop
68 END(except_vec1)
69
70 /*
71 * Cache Error
72 */
73 .org except_vec1+0x80
74 LEAF(except_vec2)
75 /*
76 * Famous last words: unreached
77 */
78 mfc0 a1,CP0_ERROREPC
79 PRINT("Cache error exception: c0_errorepc == %08x\n")
80 1: j 1b
81 nop
82 END(except_vec2)
83
84 /*
85 * General exception vector.
86 */
87 .org except_vec2+0x80
88 NESTED(except_vec3, 0, sp)
89 .set noat
90 /*
91 * Register saving is delayed as long as we don't know
92 * which registers really need to be saved.
93 */
94 mfc0 k1,CP0_CAUSE
95 la k0,exception_handlers
96 /*
97 * Next lines assumes that the used CPU type has max.
98 * 32 different types of exceptions. We might use this
99 * to implement software exceptions in the future.
100 */
101 andi k1,0x7c
102 addu k0,k1
103 lw k0,(k0)
104 NOP
105 jr k0
106 nop
107 END(except_vec3)
108 .set at
109
110 /******************************************************************************/
111
112 /*
113 * Kernel entry
114 */
115 .set noreorder
116 NESTED(kernel_entry, 16, sp)
117 /*
118 * The following two symbols are used for kernel profiling.
119 */
120 EXPORT(stext)
121 EXPORT(_stext)
122
123 #ifdef CONF_DISABLE_KSEG0_CACHING
124 /*
125 * Disable all caching for KSEG0. This option is useful
126 * when cache trouble with drivers is suspected
127 */
128 mfc0 t0,CP0_CONFIG
129 ori t0,7
130 xori t0,5
131 mtc0 t0,CP0_CONFIG
132 #endif
133 /*
134 * Clear BSS first so that there are no surprises...
135 */
136 la t0,_edata
137 la t1,_end
138 sw zero,(t0)
139 1: addiu t0,4
140 bnel t0,t1,1b
141 sw zero,(t0)
142
143 /*
144 * Initialize low level part of memory management
145 * First flush the TLB to make sure that we don't get a
146 * TLB shutdown during wire_mappings.
147 */
148 jal tlbflush
149 mtc0 zero,CP0_WIRED # delay slot
150 jal wire_mappings
151 nop
152
153 /*
154 * Stack for kernel and init
155 */
156 la sp,init_user_stack+PAGE_SIZE-24
157 la t0,init_kernel_stack+PAGE_SIZE
158 sw t0,kernelsp
159
160 /*
161 * Disable coprocessors; set ST0_CU0 to indicate that
162 * we're running on the kernel stack
163 */
164 mfc0 t0,CP0_STATUS
165 li t1,~(ST0_CU1|ST0_CU2|ST0_CU3)
166 and t0,t1
167 li t1,ST0_CU0
168 or t0,ST0_CU0
169 mtc0 t0,CP0_STATUS
170
171 1: jal start_kernel
172 nop # delay slot
173 /*
174 * Main should never return here, but
175 * just in case, we know what happens.
176 */
177 b 1b
178 nop # delay slot
179 END(kernel_entry)
180
181 /*
182 * wire_mappings - used to map hardware registers
183 */
184 LEAF(wire_mappings)
185 /*
186 * Get base address of map0 table for the
187 * the board we're running on
188 */
189 la t0,boot_info
190 lw t1,OFFSET_BOOTINFO_MACHTYPE(t0)
191 la t0,map0table
192 sll t1,PTRLOG # machtype used as index
193 addu t0,t1
194 lw t0,(t0) # get base address
195
196 /*
197 * Get number of wired TLB entries and
198 * loop over selected map0 table.
199 */
200 lw t1,(t0) # number of wired TLB entries
201 move t2,zero # TLB entry counter
202 addiu t3,t1,1 # wire one additional entry
203 beqz t1,2f # null, exit
204 mtc0 t3,CP0_WIRED # delay slot
205 addiu t0,8
206 1: lw t4,24(t0) # PageMask
207 ld t5,0(t0) # entryHi
208 ld t6,8(t0) # entryLo0
209 ld t7,16(t0) # entryLo1
210 addiu t2,1 # increment ctr
211 mtc0 t2,CP0_INDEX # set TLB entry
212 mtc0 t4,CP0_PAGEMASK
213 dmtc0 t5,CP0_ENTRYHI
214 dmtc0 t6,CP0_ENTRYLO0
215 dmtc0 t7,CP0_ENTRYLO1
216 addiu t0,32
217 bne t1,t2,1b # next TLB entry
218 tlbwi # delay slot
219
220 /*
221 * We use only 4k pages. Therefore the PageMask register
222 * is expected to be setup for 4k pages.
223 */
224 2: li t0,PM_4K
225 mtc0 t0,CP0_PAGEMASK
226
227 /*
228 * Now map the pagetables
229 */
230 mtc0 zero,CP0_INDEX
231 la t0,TLB_ROOT
232 dmtc0 t0,CP0_ENTRYHI
233 la t0,swapper_pg_dir-KSEG1
234 srl t0,6
235 ori t0,(MODE_ALIAS|MODE_GLOBAL) # uncachable, dirty, valid
236 dmtc0 t0,CP0_ENTRYLO0
237 li t0,MODE_GLOBAL
238 dmtc0 t0,CP0_ENTRYLO1
239 nop
240 tlbwi # delayed
241
242 /*
243 * Load the context register with a value that allows
244 * it to be used as fast as possible in tlb exceptions.
245 * It is expected that this register's content will
246 * NEVER be changed.
247 */
248 li t0,TLBMAP
249 dsll t0,1
250 dmtc0 t0,CP0_CONTEXT
251 jr ra # delay slot
252 nop
253 END(wire_mappings)
254
255 .data
256 /*
257 * Build an entry for table of wired entries
258 */
259 #define MAPDATA(q1,q2,q3,w1) \
260 .quad q1; \
261 .quad q2; \
262 .quad q3; \
263 .word w1; \
264 .word 0
265
266 /*
267 * Initial mapping tables for supported Mips boards.
268 * First item is always the number of wired TLB entries,
269 * following by EntryHi/EntryLo pairs and page mask.
270 * Since everything must be quad-aligned (8) we insert
271 * some dummy zeros.
272 */
273
274 /*
275 * Address table of mapping tables for supported Mips boards.
276 * Add your own stuff here but don't forget to define your
277 * target system in bootinfo.h
278 */
279
280 map0table: PTR map0_dummy # machtype = unknown
281 PTR map0_rpc # Deskstation rPC44
282 PTR map0_tyne # Deskstation Tyne
283 PTR map0_pica61 # Acer Pica-61
284 PTR map0_magnum4000 # MIPS Magnum 4000PC (RC4030)
285
286 map0_dummy: .word 0 # 0 entries
287
288 .align 3
289 /*
290 * Initial mappings for Deskstation rPC boards.
291 * RB: Untested goodie - I don't have such a board.
292 */
293 map0_rpc: .word 2 # no. of wired TLB entries
294 .word 0 # pad for alignment
295
296 MAPDATA(0xffffffffe0000000, 0x04020017, 0x00000001, PM_1M) # VESA DMA cache
297 MAPDATA(0xffffffffe2000000, 0x24000017, 0x04000017, PM_16M) # VESA I/O and memory space
298
299 /*
300 * Initial mappings for Deskstation Tyne boards.
301 */
302 map0_tyne: .word 2 # no. of wired TLB entries
303 .word 0 # pad for alignment
304
305 MAPDATA(0xffffffffe0000000, 0x04020017, 0x00000001, PM_1M) # VESA DMA cache
306 MAPDATA(0xffffffffe2000000, 0x24000017, 0x04000017, PM_16M) # VESA I/O and memory space
307
308 /*
309 * Initial mapping for ACER PICA-61 boards.
310 * FIXME: These are rather preliminary since many drivers, such as serial,
311 * parallel, scsi and ethernet need some changes to distinguish between "local"
312 * (built-in) and "optional" (ISA/PCI) I/O hardware. Local video ram is mapped
313 * to the same location as the bios maps it to. Console driver has been changed
314 * accordingly (new video type: VIDEO_TYPE_PICA_S3).
315 * FIXME: Remove or merge some of the mappings.
316 */
317 map0_pica61: .word 7 # no. wired TLB entries
318 .word 0 # dummy
319
320 MAPDATA(0xffffffffe0000000, 0x02000017, 0x00000001, PM_64K) # Local I/O space
321 MAPDATA(0xffffffffe0100000, 0x03c00017, 0x00000001, PM_4K) # Interrupt source register
322 MAPDATA(0xffffffffe0200000, 0x01800017, 0x01804017, PM_1M) # Local video control
323 MAPDATA(0xffffffffe0400000, 0x01808017, 0x0180c017, PM_1M) # Extended video control
324 MAPDATA(0xffffffffe0800000, 0x01000017, 0x01010017, PM_4M) # Local video memory (BIOS mapping)
325 MAPDATA(0xffffffffe2000000, 0x02400017, 0x02440017, PM_16M) # ISA I/O and ISA memory space (both 16M)
326 MAPDATA(0xffffffffffffe000, 0x00000001, 0x0001ffd7, PM_4K) # PCR (???)
327
328 /*
329 * Initial mapping for Mips Magnum 4000PC systems.
330 * Do you believe me now that the Acer and Mips boxes are nearly the same ? :-)
331 * FIXME: Remove or merge some of the mappings.
332 */
333
334 map0_magnum4000:
335 .word 8 # no. wired TLB entries
336 .word 0 # dummy
337
338 MAPDATA(0xffffffffe1000000, 0x03ffc013, 0x00000001, 0x7e000) # 0
339 MAPDATA(0xffffffffe0000000, 0x02000017, 0x00000001, 0x1e000) # 1 local I/O
340 MAPDATA(0xffffffffe0100000, 0x03c00017, 0x00000001, 0) # 2 IRQ source
341 MAPDATA(0xffffffffe0200000, 0x01800017, 0x01804017, 0x1fe000) # 3 local video ctrl
342 MAPDATA(0xffffffffe0400000, 0x01808017, 0x0180c017, 0x1fe000) # 4 ext. video ctrl
343 MAPDATA(0xffffffffe0800000, 0x01000017, 0x01010017, 0x7fe000) # 5 local video mem.
344 MAPDATA(0xffffffffe2000000, 0x02400017, 0x02440017, 0x1ffe000) # 6 ISA I/O and mem.
345 MAPDATA(0xffffffffffffe000, 0x00000001, 0x0001ffd7, 0) # 7 PCR
346
347
348 .text
349
350 .org 0x1000
351 .globl swapper_pg_dir
352 swapper_pg_dir = . + (KSEG1-KSEG0)
353
354 /*
355 * The page tables are initialized to only 4MB here - the final page
356 * tables are set up later depending on memory size.
357 */
358 .org 0x2000
359 EXPORT(pg0)
360
361 .org 0x3000
362 EXPORT(empty_bad_page)
363
364 .org 0x4000
365 EXPORT(empty_bad_page_table)
366
367 .org 0x5000
368 EXPORT(empty_zero_page)
369
370 .org 0x6000
371 EXPORT(invalid_pte_table)
372
373 .org 0x7000
374
375 EXPORT(cache_error_buffer)
376 .fill 32*4,1,0
377
378 .data
379 EXPORT(kernelsp)
380 PTR 0
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*/