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
   7  */
   8 #ifndef _ASM_HAZARDS_H
   9 #define _ASM_HAZARDS_H
  10
  11 #include <linux/config.h>
  12
  13 #ifdef __ASSEMBLY__
  14
  15         .macro  _ssnop
  16         sll     $0, $0, 1
  17         .endm
  18
  19         .macro  _ehb
  20         sll     $0, $0, 3
  21         .endm
  22
  23 /*
  24  * RM9000 hazards.  When the JTLB is updated by tlbwi or tlbwr, a subsequent
  25  * use of the JTLB for instructions should not occur for 4 cpu cycles and use
  26  * for data translations should not occur for 3 cpu cycles.
  27  */
  28 #ifdef CONFIG_CPU_RM9000
  29
  30         .macro  mtc0_tlbw_hazard
  31         .set    push
  32         .set    mips32
  33         _ssnop; _ssnop; _ssnop; _ssnop
  34         .set    pop
  35         .endm
  36
  37         .macro  tlbw_eret_hazard
  38         .set    push
  39         .set    mips32
  40         _ssnop; _ssnop; _ssnop; _ssnop
  41         .set    pop
  42         .endm
  43
  44 #else
  45
  46 /*
  47  * The taken branch will result in a two cycle penalty for the two killed
  48  * instructions on R4000 / R4400.  Other processors only have a single cycle
  49  * hazard so this is nice trick to have an optimal code for a range of
  50  * processors.
  51  */
  52         .macro  mtc0_tlbw_hazard
  53         b       . + 8
  54         .endm
  55
  56         .macro  tlbw_eret_hazard
  57         .endm
  58 #endif
  59
  60 /*
  61  * mtc0->mfc0 hazard
  62  * The 24K has a 2 cycle mtc0/mfc0 execution hazard.
  63  * It is a MIPS32R2 processor so ehb will clear the hazard.
  64  */
  65
  66 #ifdef CONFIG_CPU_MIPSR2
  67 /*
  68  * Use a macro for ehb unless explicit support for MIPSR2 is enabled
  69  */
  70
  71 #define irq_enable_hazard
  72         _ehb
  73
  74 #define irq_disable_hazard
  75         _ehb
  76
  77 #elif defined(CONFIG_CPU_R10000) || defined(CONFIG_CPU_RM9000) || \
  78       defined(CONFIG_CPU_SB1)
  79
  80 /*
  81  * R10000 rocks - all hazards handled in hardware, so this becomes a nobrainer.
  82  */
  83
  84 #define irq_enable_hazard
  85
  86 #define irq_disable_hazard
  87
  88 #else
  89
  90 /*
  91  * Classic MIPS needs 1 - 3 nops or ssnops
  92  */
  93 #define irq_enable_hazard
  94 #define irq_disable_hazard                                              \
  95         _ssnop; _ssnop; _ssnop
  96
  97 #endif
  98
  99 #else /* __ASSEMBLY__ */
 100
 101 __asm__(
 102         "       .macro  _ssnop                                  \n\t"
 103         "       sll     $0, $0, 1                               \n\t"
 104         "       .endm                                           \n\t"
 105         "                                                       \n\t"
 106         "       .macro  _ehb                                    \n\t"
 107         "       sll     $0, $0, 3                               \n\t"
 108         "       .endm                                           \n\t");
 109
 110 #ifdef CONFIG_CPU_RM9000
 111
 112 /*
 113  * RM9000 hazards.  When the JTLB is updated by tlbwi or tlbwr, a subsequent
 114  * use of the JTLB for instructions should not occur for 4 cpu cycles and use
 115  * for data translations should not occur for 3 cpu cycles.
 116  */
 117
 118 #define mtc0_tlbw_hazard()                                              \
 119         __asm__ __volatile__(                                           \
 120                 ".set\tmips32\n\t"                                      \
 121                 "_ssnop; _ssnop; _ssnop; _ssnop\n\t"                    \
 122                 ".set\tmips0")
 123
 124 #define tlbw_use_hazard()                                               \
 125         __asm__ __volatile__(                                           \
 126                 ".set\tmips32\n\t"                                      \
 127                 "_ssnop; _ssnop; _ssnop; _ssnop\n\t"                    \
 128                 ".set\tmips0")
 129
 130 #define back_to_back_c0_hazard()        do { } while (0)
 131
 132 #else
 133
 134 /*
 135  * Overkill warning ...
 136  */
 137 #define mtc0_tlbw_hazard()                                              \
 138         __asm__ __volatile__(                                           \
 139                 ".set noreorder\n\t"                                    \
 140                 "nop; nop; nop; nop; nop; nop;\n\t"                     \
 141                 ".set reorder\n\t")
 142
 143 #define tlbw_use_hazard()                                               \
 144         __asm__ __volatile__(                                           \
 145                 ".set noreorder\n\t"                                    \
 146                 "nop; nop; nop; nop; nop; nop;\n\t"                     \
 147                 ".set reorder\n\t")
 148
 149 #endif
 150
 151 /*
 152  * Interrupt enable/disable hazards
 153  * Some processors have hazards when modifying
 154  * the status register to change the interrupt state
 155  */
 156
 157 #ifdef CONFIG_CPU_MIPSR2
 158
 159 __asm__(
 160         "       .macro\tirq_enable_hazard                       \n\t"
 161         "       _ehb                                            \n\t"
 162         "       .endm                                           \n\t"
 163         "                                                       \n\t"
 164         "       .macro\tirq_disable_hazard                      \n\t"
 165         "       _ehb                                            \n\t"
 166         "       .endm                                           \n\t"
 167         "                                                       \n\t"
 168         "       .macro\tback_to_back_c0_hazard                  \n\t"
 169         "       _ehb                                            \n\t"
 170         "       .endm");
 171
 172 #define irq_enable_hazard()                                             \
 173         __asm__ __volatile__(                                           \
 174         "irq_enable_hazard")
 175
 176 #define irq_disable_hazard()                                            \
 177         __asm__ __volatile__(                                           \
 178         "irq_disable_hazard")
 179
 180 #define back_to_back_c0_hazard()                                        \
 181         __asm__ __volatile__(                                           \
 182         "back_to_back_c0_hazard")
 183
 184 #elif defined(CONFIG_CPU_R10000) || defined(CONFIG_CPU_RM9000) || \
 185       defined(CONFIG_CPU_SB1)
 186
 187 /*
 188  * R10000 rocks - all hazards handled in hardware, so this becomes a nobrainer.
 189  */
 190
 191 __asm__(
 192         "       .macro\tirq_enable_hazard                       \n\t"
 193         "       .endm                                           \n\t"
 194         "                                                       \n\t"
 195         "       .macro\tirq_disable_hazard                      \n\t"
 196         "       .endm");
 197
 198 #define irq_enable_hazard()     do { } while (0)
 199 #define irq_disable_hazard()    do { } while (0)
 200
 201 #define back_to_back_c0_hazard()        do { } while (0)
 202
 203 #else
 204
 205 /*
 206  * Default for classic MIPS processors.  Assume worst case hazards but don't
 207  * care about the irq_enable_hazard - sooner or later the hardware will
 208  * enable it and we don't care when exactly.
 209  */
 210
 211 __asm__(
 212         "       #                                               \n\t"
 213         "       # There is a hazard but we do not care          \n\t"
 214         "       #                                               \n\t"
 215         "       .macro\tirq_enable_hazard                       \n\t"
 216         "       .endm                                           \n\t"
 217         "                                                       \n\t"
 218         "       .macro\tirq_disable_hazard                      \n\t"
 219         "       _ssnop; _ssnop; _ssnop                          \n\t"
 220         "       .endm");
 221
 222 #define irq_enable_hazard()     do { } while (0)
 223 #define irq_disable_hazard()                                            \
 224         __asm__ __volatile__(                                           \
 225         "irq_disable_hazard")
 226
 227 #define back_to_back_c0_hazard()                                        \
 228         __asm__ __volatile__(                                           \
 229         "       .set noreorder                          \n"             \
 230         "       nop; nop; nop                           \n"             \
 231         "       .set reorder                            \n")
 232
 233 #endif
 234
 235 #ifdef CONFIG_CPU_MIPSR2
 236 /*
 237  * gcc has a tradition of misscompiling the previous construct using the
 238  * address of a label as argument to inline assembler.  Gas otoh has the
 239  * annoying difference between la and dla which are only usable for 32-bit
 240  * rsp. 64-bit code, so can't be used without conditional compilation.
 241  * The alterantive is switching the assembler to 64-bit code which happens
 242  * to work right even for 32-bit code ...
 243  */
 244 #define instruction_hazard()                                            \
 245 do {                                                                    \
 246         unsigned long tmp;                                              \
 247                                                                         \
 248         __asm__ __volatile__(                                           \
 249         "       .set    mips64r2                                \n"     \
 250         "       dla     %0, 1f                                  \n"     \
 251         "       jr.hb   %0                                      \n"     \
 252         "       .set    mips0                                   \n"     \
 253         "1:                                                     \n"     \
 254         : "=r" (tmp));                                                  \
 255 } while (0)
 256
 257 #else
 258 #define instruction_hazard() do { } while (0)
 259 #endif
 260
 261 #endif /* __ASSEMBLY__ */
 262
 263 #endif /* _ASM_HAZARDS_H */