include/asm-mips/hazards.h

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Copyright (C) 2003, 2004 Ralf Baechle <ralf@linux-mips.org>
   7  * Copyright (C) MIPS Technologies, Inc.
   8  *   written by Ralf Baechle <ralf@linux-mips.org>
   9  */
  10 #ifndef _ASM_HAZARDS_H
  11 #define _ASM_HAZARDS_H
  12
  13 #include <linux/config.h>
  14
  15 #ifdef __ASSEMBLY__
  16
  17         .macro  _ssnop
  18         sll     $0, $0, 1
  19         .endm
  20
  21         .macro  _ehb
  22         sll     $0, $0, 3
  23         .endm
  24
  25 /*
  26  * RM9000 hazards.  When the JTLB is updated by tlbwi or tlbwr, a subsequent
  27  * use of the JTLB for instructions should not occur for 4 cpu cycles and use
  28  * for data translations should not occur for 3 cpu cycles.
  29  */
  30 #ifdef CONFIG_CPU_RM9000
  31
  32         .macro  mtc0_tlbw_hazard
  33         .set    push
  34         .set    mips32
  35         _ssnop; _ssnop; _ssnop; _ssnop
  36         .set    pop
  37         .endm
  38
  39         .macro  tlbw_eret_hazard
  40         .set    push
  41         .set    mips32
  42         _ssnop; _ssnop; _ssnop; _ssnop
  43         .set    pop
  44         .endm
  45
  46 #else
  47
  48 /*
  49  * The taken branch will result in a two cycle penalty for the two killed
  50  * instructions on R4000 / R4400.  Other processors only have a single cycle
  51  * hazard so this is nice trick to have an optimal code for a range of
  52  * processors.
  53  */
  54         .macro  mtc0_tlbw_hazard
  55         b       . + 8
  56         .endm
  57
  58         .macro  tlbw_eret_hazard
  59         .endm
  60 #endif
  61
  62 /*
  63  * mtc0->mfc0 hazard
  64  * The 24K has a 2 cycle mtc0/mfc0 execution hazard.
  65  * It is a MIPS32R2 processor so ehb will clear the hazard.
  66  */
  67
  68 #ifdef CONFIG_CPU_MIPSR2
  69 /*
  70  * Use a macro for ehb unless explicit support for MIPSR2 is enabled
  71  */
  72
  73 #define irq_enable_hazard
  74         _ehb
  75
  76 #define irq_disable_hazard
  77         _ehb
  78
  79 #elif defined(CONFIG_CPU_R10000) || defined(CONFIG_CPU_RM9000)
  80
  81 /*
  82  * R10000 rocks - all hazards handled in hardware, so this becomes a nobrainer.
  83  */
  84
  85 #define irq_enable_hazard
  86
  87 #define irq_disable_hazard
  88
  89 #else
  90
  91 /*
  92  * Classic MIPS needs 1 - 3 nops or ssnops
  93  */
  94 #define irq_enable_hazard
  95 #define irq_disable_hazard                                              \
  96         _ssnop; _ssnop; _ssnop
  97
  98 #endif
  99
 100 #else /* __ASSEMBLY__ */
 101
 102 __asm__(
 103         "       .macro  _ssnop                                  \n"
 104         "       sll     $0, $0, 1                               \n"
 105         "       .endm                                           \n"
 106         "                                                       \n"
 107         "       .macro  _ehb                                    \n"
 108         "       sll     $0, $0, 3                               \n"
 109         "       .endm                                           \n");
 110
 111 #ifdef CONFIG_CPU_RM9000
 112
 113 /*
 114  * RM9000 hazards.  When the JTLB is updated by tlbwi or tlbwr, a subsequent
 115  * use of the JTLB for instructions should not occur for 4 cpu cycles and use
 116  * for data translations should not occur for 3 cpu cycles.
 117  */
 118
 119 #define mtc0_tlbw_hazard()                                              \
 120         __asm__ __volatile__(                                           \
 121         "       .set    mips32                                  \n"     \
 122         "       _ssnop                                          \n"     \
 123         "       _ssnop                                          \n"     \
 124         "       _ssnop                                          \n"     \
 125         "       _ssnop                                          \n"     \
 126         "       .set    mips0                                   \n")
 127
 128 #define tlbw_use_hazard()                                               \
 129         __asm__ __volatile__(                                           \
 130         "       .set    mips32                                  \n"     \
 131         "       _ssnop                                          \n"     \
 132         "       _ssnop                                          \n"     \
 133         "       _ssnop                                          \n"     \
 134         "       _ssnop                                          \n"     \
 135         "       .set    mips0                                   \n")
 136
 137 #else
 138
 139 /*
 140  * Overkill warning ...
 141  */
 142 #define mtc0_tlbw_hazard()                                              \
 143         __asm__ __volatile__(                                           \
 144         "       .set    noreorder                               \n"     \
 145         "       nop                                             \n"     \
 146         "       nop                                             \n"     \
 147         "       nop                                             \n"     \
 148         "       nop                                             \n"     \
 149         "       nop                                             \n"     \
 150         "       nop                                             \n"     \
 151         "       .set    reorder                                 \n")
 152
 153 #define tlbw_use_hazard()                                               \
 154         __asm__ __volatile__(                                           \
 155         "       .set    noreorder                               \n"     \
 156         "       nop                                             \n"     \
 157         "       nop                                             \n"     \
 158         "       nop                                             \n"     \
 159         "       nop                                             \n"     \
 160         "       nop                                             \n"     \
 161         "       nop                                             \n"     \
 162         "       .set    reorder                                 \n")
 163
 164 #endif
 165
 166 /*
 167  * Interrupt enable/disable hazards
 168  * Some processors have hazards when modifying
 169  * the status register to change the interrupt state
 170  */
 171
 172 #ifdef CONFIG_CPU_MIPSR2
 173
 174 __asm__("       .macro  irq_enable_hazard                       \n"
 175         "       _ehb                                            \n"
 176         "       .endm                                           \n"
 177         "                                                       \n"
 178         "       .macro  irq_disable_hazard                      \n"
 179         "       _ehb                                            \n"
 180         "       .endm                                           \n");
 181
 182 #elif defined(CONFIG_CPU_R10000) || defined(CONFIG_CPU_RM9000)
 183
 184 /*
 185  * R10000 rocks - all hazards handled in hardware, so this becomes a nobrainer.
 186  */
 187
 188 __asm__(
 189         "       .macro  irq_enable_hazard                       \n"
 190         "       .endm                                           \n"
 191         "                                                       \n"
 192         "       .macro  irq_disable_hazard                      \n"
 193         "       .endm                                           \n");
 194
 195 #else
 196
 197 /*
 198  * Default for classic MIPS processors.  Assume worst case hazards but don't
 199  * care about the irq_enable_hazard - sooner or later the hardware will
 200  * enable it and we don't care when exactly.
 201  */
 202
 203 __asm__(
 204         "       #                                               \n"
 205         "       # There is a hazard but we do not care          \n"
 206         "       #                                               \n"
 207         "       .macro\tirq_enable_hazard                       \n"
 208         "       .endm                                           \n"
 209         "                                                       \n"
 210         "       .macro\tirq_disable_hazard                      \n"
 211         "       _ssnop                                          \n"
 212         "       _ssnop                                          \n"
 213         "       _ssnop                                          \n"
 214         "       .endm                                           \n");
 215
 216 #endif
 217
 218 #define irq_enable_hazard()                                             \
 219         __asm__ __volatile__("irq_enable_hazard")
 220 #define irq_disable_hazard()                                            \
 221         __asm__ __volatile__("irq_disable_hazard")
 222
 223
 224 /*
 225  * Back-to-back hazards -
 226  *
 227  * What is needed to separate a move to cp0 from a subsequent read from the
 228  * same cp0 register?
 229  */
 230 #ifdef CONFIG_CPU_MIPSR2
 231
 232 __asm__("       .macro  back_to_back_c0_hazard                  \n"
 233         "       _ehb                                            \n"
 234         "       .endm                                           \n");
 235
 236 #elif defined(CONFIG_CPU_R10000) || defined(CONFIG_CPU_RM9000) || \
 237       defined(CONFIG_CPU_SB1)
 238
 239 __asm__("       .macro  back_to_back_c0_hazard                  \n"
 240         "       .endm                                           \n");
 241
 242 #else
 243
 244 __asm__("       .macro  back_to_back_c0_hazard                  \n"
 245         "       .set    noreorder                               \n"
 246         "       _ssnop                                          \n"
 247         "       _ssnop                                          \n"
 248         "       _ssnop                                          \n"
 249         "       .set    reorder                                 \n"
 250         "       .endm");
 251
 252 #endif
 253
 254 #define back_to_back_c0_hazard()                                        \
 255         __asm__ __volatile__("back_to_back_c0_hazard")
 256
 257
 258 /*
 259  * Instruction execution hazard
 260  */
 261 #ifdef CONFIG_CPU_MIPSR2
 262 /*
 263  * gcc has a tradition of misscompiling the previous construct using the
 264  * address of a label as argument to inline assembler.  Gas otoh has the
 265  * annoying difference between la and dla which are only usable for 32-bit
 266  * rsp. 64-bit code, so can't be used without conditional compilation.
 267  * The alterantive is switching the assembler to 64-bit code which happens
 268  * to work right even for 32-bit code ...
 269  */
 270 #define instruction_hazard()                                            \
 271 do {                                                                    \
 272         unsigned long tmp;                                              \
 273                                                                         \
 274         __asm__ __volatile__(                                           \
 275         "       .set    mips64r2                                \n"     \
 276         "       dla     %0, 1f                                  \n"     \
 277         "       jr.hb   %0                                      \n"     \
 278         "       .set    mips0                                   \n"     \
 279         "1:                                                     \n"     \
 280         : "=r" (tmp));                                                  \
 281 } while (0)
 282
 283 #else
 284 #define instruction_hazard() do { } while (0)
 285 #endif
 286
 287 extern void mips_ihb(void);
 288
 289 #endif /* __ASSEMBLY__ */
 290
 291 #endif /* _ASM_HAZARDS_H */