1/* $Id: head.S,v 1.7 2003/09/01 17:58:19 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 /* 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 80 ! 81 mov.l 2f, r0 82 mov r0, r15 ! Set initial r15 (stack pointer) 83#ifdef CONFIG_CPU_HAS_SR_RB 84 mov.l 7f, r0 85 ldc r0, r7_bank ! ... and initial thread_info 86#endif 87 88#ifdef CONFIG_PMB 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 134 * r11 = scratch register 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 143 144 mov #PMB_E_SHIFT, r0 145 mov #0x1, r4 146 shld r0, r4 147 148 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 152 153 /* 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: 170 171 mov.l .LPMB_DATA_MASK, r11 172 mov.l @r7, r8 173 and r11, r8 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 */ 188 mov #0, r10 189 190#ifdef CONFIG_UNCACHED_MAPPING 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 210#endif 211 212/* 213 * Iterate over all of the available sizes from largest to 214 * smallest for constructing the cached mapping. 215 */ 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 */ \ 242 add #1, r10; \ 243 \ 244 sub r6, r5; \ 245 add r6, r0; \ 246 add r6, r2; \ 247 \ 248 bra .L##size; \ 2499999: 250 251 __PMB_ITER_BY_SIZE(512) 252 __PMB_ITER_BY_SIZE(128) 253 __PMB_ITER_BY_SIZE(64) 254 __PMB_ITER_BY_SIZE(16) 255 256#ifdef CONFIG_UNCACHED_MAPPING 257 /* 258 * Now that we can access it, update cached_to_uncached and 259 * uncached_size. 260 */ 261 mov.l .Lcached_to_uncached, r0 262 mov.l r7, @r0 263 264 mov.l .Luncached_size, r0 265 mov #1, r7 266 shll16 r7 267 shll8 r7 268 mov.l r7, @r0 269#endif 270 271 /* 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 278 mov #NR_PMB_ENTRIES, r0 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 289 290.Lpmb_done: 291#endif /* CONFIG_PMB */ 292 293#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 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 305 306 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 313 31410: 315#endif 316 317 ! Additional CPU initialization 318 mov.l 6f, r0 319 jsr @r0 320 nop 321 322 SYNCO() ! Wait for pending instructions.. 323 324 ! Start kernel 325 mov.l 5f, r0 326 jmp @r0 327 nop 328 329 .balign 4 330#if defined(CONFIG_CPU_SH2) 3311: .long 0x000000F0 ! IMASK=0xF 332#else 3331: .long 0x400080F0 ! MD=1, RB=0, BL=0, FD=1, IMASK=0xF 334#endif 335ENTRY(stack_start) 3362: .long init_thread_union+THREAD_SIZE 3373: .long __bss_start 3384: .long _end 3395: .long start_kernel 3406: .long cpu_init 3417: .long init_thread_union 342 343#ifdef CONFIG_PMB 344.LPMB_ADDR: .long PMB_ADDR 345.LPMB_DATA: .long PMB_DATA 346.LPMB_DATA_MASK: .long PMB_PFN_MASK | PMB_V 347.LFIRST_ADDR_ENTRY: .long PAGE_OFFSET | PMB_V 348.LFIRST_DATA_ENTRY: .long __MEMORY_START | PMB_V 349.LMMUCR: .long MMUCR 350.LMEMORY_SIZE: .long __MEMORY_SIZE 351#ifdef CONFIG_UNCACHED_MAPPING 352.Lcached_to_uncached: .long cached_to_uncached 353.Luncached_size: .long uncached_size 354#endif 355#endif 356