include/asm-xtensa/mmu_context.h

   1 /*
   2  * include/asm-xtensa/mmu_context.h
   3  *
   4  * Switch an MMU context.
   5  *
   6  * This file is subject to the terms and conditions of the GNU General Public
   7  * License.  See the file "COPYING" in the main directory of this archive
   8  * for more details.
   9  *
  10  * Copyright (C) 2001 - 2005 Tensilica Inc.
  11  */
  12
  13 #ifndef _XTENSA_MMU_CONTEXT_H
  14 #define _XTENSA_MMU_CONTEXT_H
  15
  16 #include <linux/config.h>
  17 #include <linux/stringify.h>
  18
  19 #include <asm/pgtable.h>
  20 #include <asm/mmu_context.h>
  21 #include <asm/cacheflush.h>
  22 #include <asm/tlbflush.h>
  23
  24 /*
  25  * Linux was ported to Xtensa assuming all auto-refill ways in set 0
  26  * had the same properties (a very likely assumption).  Multiple sets
  27  * of auto-refill ways will still work properly, but not as optimally
  28  * as the Xtensa designer may have assumed.
  29  *
  30  * We make this case a hard #error, killing the kernel build, to alert
  31  * the developer to this condition (which is more likely an error).
  32  * You super-duper clever developers can change it to a warning or
  33  * remove it altogether if you think you know what you're doing.  :)
  34  */
  35
  36 #if (XCHAL_HAVE_TLBS != 1)
  37 # error "Linux must have an MMU!"
  38 #endif
  39
  40 #if ((XCHAL_ITLB_ARF_WAYS == 0) || (XCHAL_DTLB_ARF_WAYS == 0))
  41 # error "MMU must have auto-refill ways"
  42 #endif
  43
  44 #if ((XCHAL_ITLB_ARF_SETS != 1) || (XCHAL_DTLB_ARF_SETS != 1))
  45 # error Linux may not use all auto-refill ways as efficiently as you think
  46 #endif
  47
  48 #if (XCHAL_MMU_MAX_PTE_PAGE_SIZE != XCHAL_MMU_MIN_PTE_PAGE_SIZE)
  49 # error Only one page size allowed!
  50 #endif
  51
  52 extern unsigned long asid_cache;
  53 extern pgd_t *current_pgd;
  54
  55 /*
  56  * Define the number of entries per auto-refill way in set 0 of both I and D
  57  * TLBs.  We deal only with set 0 here (an assumption further explained in
  58  * assertions.h).  Also, define the total number of ARF entries in both TLBs.
  59  */
  60
  61 #define ITLB_ENTRIES_PER_ARF_WAY  (XCHAL_ITLB_SET(XCHAL_ITLB_ARF_SET0,ENTRIES))
  62 #define DTLB_ENTRIES_PER_ARF_WAY  (XCHAL_DTLB_SET(XCHAL_DTLB_ARF_SET0,ENTRIES))
  63
  64 #define ITLB_ENTRIES                                                    \
  65         (ITLB_ENTRIES_PER_ARF_WAY * (XCHAL_ITLB_SET(XCHAL_ITLB_ARF_SET0,WAYS)))
  66 #define DTLB_ENTRIES                                                    \
  67         (DTLB_ENTRIES_PER_ARF_WAY * (XCHAL_DTLB_SET(XCHAL_DTLB_ARF_SET0,WAYS)))
  68
  69
  70 /*
  71  * SMALLEST_NTLB_ENTRIES is the smaller of ITLB_ENTRIES and DTLB_ENTRIES.
  72  * In practice, they are probably equal.  This macro simplifies function
  73  * flush_tlb_range().
  74  */
  75
  76 #if (DTLB_ENTRIES < ITLB_ENTRIES)
  77 # define SMALLEST_NTLB_ENTRIES  DTLB_ENTRIES
  78 #else
  79 # define SMALLEST_NTLB_ENTRIES  ITLB_ENTRIES
  80 #endif
  81
  82
  83 /*
  84  * asid_cache tracks only the ASID[USER_RING] field of the RASID special
  85  * register, which is the current user-task asid allocation value.
  86  * mm->context has the same meaning.  When it comes time to write the
  87  * asid_cache or mm->context values to the RASID special register, we first
  88  * shift the value left by 8, then insert the value.
  89  * ASID[0] always contains the kernel's asid value, and we reserve three
  90  * other asid values that we never assign to user tasks.
  91  */
  92
  93 #define ASID_INC        0x1
  94 #define ASID_MASK       ((1 << XCHAL_MMU_ASID_BITS) - 1)
  95
  96 /*
  97  * XCHAL_MMU_ASID_INVALID is a configurable Xtensa processor constant
  98  * indicating invalid address space.  XCHAL_MMU_ASID_KERNEL is a configurable
  99  * Xtensa processor constant indicating the kernel address space.  They can
 100  * be arbitrary values.
 101  *
 102  * We identify three more unique, reserved ASID values to use in the unused
 103  * ring positions.  No other user process will be assigned these reserved
 104  * ASID values.
 105  *
 106  * For example, given that
 107  *
 108  *      XCHAL_MMU_ASID_INVALID == 0
 109  *      XCHAL_MMU_ASID_KERNEL  == 1
 110  *
 111  * the following maze of #if statements would generate
 112  *
 113  *      ASID_RESERVED_1        == 2
 114  *      ASID_RESERVED_2        == 3
 115  *      ASID_RESERVED_3        == 4
 116  *      ASID_FIRST_NONRESERVED == 5
 117  */
 118
 119 #if (XCHAL_MMU_ASID_INVALID != XCHAL_MMU_ASID_KERNEL + 1)
 120 # define ASID_RESERVED_1         ((XCHAL_MMU_ASID_KERNEL + 1) & ASID_MASK)
 121 #else
 122 # define ASID_RESERVED_1         ((XCHAL_MMU_ASID_KERNEL + 2) & ASID_MASK)
 123 #endif
 124
 125 #if (XCHAL_MMU_ASID_INVALID != ASID_RESERVED_1 + 1)
 126 # define ASID_RESERVED_2         ((ASID_RESERVED_1 + 1) & ASID_MASK)
 127 #else
 128 # define ASID_RESERVED_2         ((ASID_RESERVED_1 + 2) & ASID_MASK)
 129 #endif
 130
 131 #if (XCHAL_MMU_ASID_INVALID != ASID_RESERVED_2 + 1)
 132 # define ASID_RESERVED_3         ((ASID_RESERVED_2 + 1) & ASID_MASK)
 133 #else
 134 # define ASID_RESERVED_3         ((ASID_RESERVED_2 + 2) & ASID_MASK)
 135 #endif
 136
 137 #if (XCHAL_MMU_ASID_INVALID != ASID_RESERVED_3 + 1)
 138 # define ASID_FIRST_NONRESERVED  ((ASID_RESERVED_3 + 1) & ASID_MASK)
 139 #else
 140 # define ASID_FIRST_NONRESERVED  ((ASID_RESERVED_3 + 2) & ASID_MASK)
 141 #endif
 142
 143 #define ASID_ALL_RESERVED ( ((ASID_RESERVED_1) << 24) + \
 144                             ((ASID_RESERVED_2) << 16) + \
 145                             ((ASID_RESERVED_3) <<  8) + \
 146                             ((XCHAL_MMU_ASID_KERNEL))   )
 147
 148
 149 /*
 150  * NO_CONTEXT is the invalid ASID value that we don't ever assign to
 151  * any user or kernel context.  NO_CONTEXT is a better mnemonic than
 152  * XCHAL_MMU_ASID_INVALID, so we use it in code instead.
 153  */
 154
 155 #define NO_CONTEXT   XCHAL_MMU_ASID_INVALID
 156
 157 #if (KERNEL_RING != 0)
 158 # error The KERNEL_RING really should be zero.
 159 #endif
 160
 161 #if (USER_RING >= XCHAL_MMU_RINGS)
 162 # error USER_RING cannot be greater than the highest numbered ring.
 163 #endif
 164
 165 #if (USER_RING == KERNEL_RING)
 166 # error The user and kernel rings really should not be equal.
 167 #endif
 168
 169 #if (USER_RING == 1)
 170 #define ASID_INSERT(x) ( ((ASID_RESERVED_1)   << 24) + \
 171                          ((ASID_RESERVED_2)   << 16) + \
 172                          (((x) & (ASID_MASK)) <<  8) + \
 173                          ((XCHAL_MMU_ASID_KERNEL))   )
 174
 175 #elif (USER_RING == 2)
 176 #define ASID_INSERT(x) ( ((ASID_RESERVED_1)   << 24) + \
 177                          (((x) & (ASID_MASK)) << 16) + \
 178                          ((ASID_RESERVED_2)   <<  8) + \
 179                          ((XCHAL_MMU_ASID_KERNEL))   )
 180
 181 #elif (USER_RING == 3)
 182 #define ASID_INSERT(x) ( (((x) & (ASID_MASK)) << 24) + \
 183                          ((ASID_RESERVED_1)   << 16) + \
 184                          ((ASID_RESERVED_2)   <<  8) + \
 185                          ((XCHAL_MMU_ASID_KERNEL))   )
 186
 187 #else
 188 #error Goofy value for USER_RING
 189
 190 #endif /* USER_RING == 1 */
 191
 192
 193 /*
 194  *  All unused by hardware upper bits will be considered
 195  *  as a software asid extension.
 196  */
 197
 198 #define ASID_VERSION_MASK  ((unsigned long)~(ASID_MASK|(ASID_MASK-1)))
 199 #define ASID_FIRST_VERSION                                              \
 200         ((unsigned long)(~ASID_VERSION_MASK) + 1 + ASID_FIRST_NONRESERVED)
 201
 202 static inline void set_rasid_register (unsigned long val)
 203 {
 204         __asm__ __volatile__ (" wsr %0, "__stringify(RASID)"\n\t"
 205                               " isync\n" : : "a" (val));
 206 }
 207
 208 static inline unsigned long get_rasid_register (void)
 209 {
 210         unsigned long tmp;
 211         __asm__ __volatile__ (" rsr %0, "__stringify(RASID)"\n\t" : "=a" (tmp));
 212         return tmp;
 213 }
 214
 215
 216 #if ((XCHAL_MMU_ASID_INVALID == 0) && (XCHAL_MMU_ASID_KERNEL == 1))
 217
 218 static inline void
 219 get_new_mmu_context(struct mm_struct *mm, unsigned long asid)
 220 {
 221         extern void flush_tlb_all(void);
 222         if (! ((asid += ASID_INC) & ASID_MASK) ) {
 223                 flush_tlb_all(); /* start new asid cycle */
 224                 if (!asid)      /* fix version if needed */
 225                         asid = ASID_FIRST_VERSION - ASID_FIRST_NONRESERVED;
 226                 asid += ASID_FIRST_NONRESERVED;
 227         }
 228         mm->context = asid_cache = asid;
 229 }
 230
 231 #else
 232 #warning ASID_{INVALID,KERNEL} values impose non-optimal get_new_mmu_context implementation
 233
 234 /* XCHAL_MMU_ASID_INVALID == 0 and XCHAL_MMU_ASID_KERNEL ==1 are
 235    really the best, but if you insist... */
 236
 237 static inline int validate_asid (unsigned long asid)
 238 {
 239         switch (asid) {
 240         case XCHAL_MMU_ASID_INVALID:
 241         case XCHAL_MMU_ASID_KERNEL:
 242         case ASID_RESERVED_1:
 243         case ASID_RESERVED_2:
 244         case ASID_RESERVED_3:
 245                 return 0; /* can't use these values as ASIDs */
 246         }
 247         return 1; /* valid */
 248 }
 249
 250 static inline void
 251 get_new_mmu_context(struct mm_struct *mm, unsigned long asid)
 252 {
 253         extern void flush_tlb_all(void);
 254         while (1) {
 255                 asid += ASID_INC;
 256                 if ( ! (asid & ASID_MASK) ) {
 257                         flush_tlb_all(); /* start new asid cycle */
 258                         if (!asid)      /* fix version if needed */
 259                                 asid = ASID_FIRST_VERSION - ASID_FIRST_NONRESERVED;
 260                         asid += ASID_FIRST_NONRESERVED;
 261                         break; /* no need to validate here */
 262                 }
 263                 if (validate_asid (asid & ASID_MASK))
 264                         break;
 265         }
 266         mm->context = asid_cache = asid;
 267 }
 268
 269 #endif
 270
 271
 272 /*
 273  * Initialize the context related info for a new mm_struct
 274  * instance.
 275  */
 276
 277 static inline int
 278 init_new_context(struct task_struct *tsk, struct mm_struct *mm)
 279 {
 280         mm->context = NO_CONTEXT;
 281         return 0;
 282 }
 283
 284 static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
 285                              struct task_struct *tsk)
 286 {
 287         unsigned long asid = asid_cache;
 288
 289         /* Check if our ASID is of an older version and thus invalid */
 290
 291         if ((next->context ^ asid) & ASID_VERSION_MASK)
 292                 get_new_mmu_context(next, asid);
 293
 294         set_rasid_register (ASID_INSERT(next->context));
 295         invalidate_page_directory();
 296 }
 297
 298 #define deactivate_mm(tsk, mm)  do { } while(0)
 299
 300 /*
 301  * Destroy context related info for an mm_struct that is about
 302  * to be put to rest.
 303  */
 304 static inline void destroy_context(struct mm_struct *mm)
 305 {
 306         /* Nothing to do. */
 307 }
 308
 309 /*
 310  * After we have set current->mm to a new value, this activates
 311  * the context for the new mm so we see the new mappings.
 312  */
 313 static inline void
 314 activate_mm(struct mm_struct *prev, struct mm_struct *next)
 315 {
 316         /* Unconditionally get a new ASID.  */
 317
 318         get_new_mmu_context(next, asid_cache);
 319         set_rasid_register (ASID_INSERT(next->context));
 320         invalidate_page_directory();
 321 }
 322
 323
 324 static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
 325 {
 326         /* Nothing to do. */
 327
 328 }
 329
 330 #endif /* _XTENSA_MMU_CONTEXT_H */