arch/x86/kernel/cpu/mtrr/centaur.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/init.h>
   3 #include <linux/mm.h>
   4
   5 #include <asm/mtrr.h>
   6 #include <asm/msr.h>
   7
   8 #include "mtrr.h"
   9
  10 static struct {
  11         unsigned long high;
  12         unsigned long low;
  13 } centaur_mcr[8];
  14
  15 static u8 centaur_mcr_reserved;
  16 static u8 centaur_mcr_type;     /* 0 for winchip, 1 for winchip2 */
  17
  18 /**
  19  * centaur_get_free_region - Get a free MTRR.
  20  *
  21  * @base: The starting (base) address of the region.
  22  * @size: The size (in bytes) of the region.
  23  *
  24  * Returns: the index of the region on success, else -1 on error.
  25  */
  26 static int
  27 centaur_get_free_region(unsigned long base, unsigned long size, int replace_reg)
  28 {
  29         unsigned long lbase, lsize;
  30         mtrr_type ltype;
  31         int i, max;
  32
  33         max = num_var_ranges;
  34         if (replace_reg >= 0 && replace_reg < max)
  35                 return replace_reg;
  36
  37         for (i = 0; i < max; ++i) {
  38                 if (centaur_mcr_reserved & (1 << i))
  39                         continue;
  40                 mtrr_if->get(i, &lbase, &lsize, &ltype);
  41                 if (lsize == 0)
  42                         return i;
  43         }
  44
  45         return -ENOSPC;
  46 }
  47
  48 static void
  49 centaur_get_mcr(unsigned int reg, unsigned long *base,
  50                 unsigned long *size, mtrr_type * type)
  51 {
  52         *base = centaur_mcr[reg].high >> PAGE_SHIFT;
  53         *size = -(centaur_mcr[reg].low & 0xfffff000) >> PAGE_SHIFT;
  54         *type = MTRR_TYPE_WRCOMB;               /* write-combining  */
  55
  56         if (centaur_mcr_type == 1 && ((centaur_mcr[reg].low & 31) & 2))
  57                 *type = MTRR_TYPE_UNCACHABLE;
  58         if (centaur_mcr_type == 1 && (centaur_mcr[reg].low & 31) == 25)
  59                 *type = MTRR_TYPE_WRBACK;
  60         if (centaur_mcr_type == 0 && (centaur_mcr[reg].low & 31) == 31)
  61                 *type = MTRR_TYPE_WRBACK;
  62 }
  63
  64 static void
  65 centaur_set_mcr(unsigned int reg, unsigned long base,
  66                 unsigned long size, mtrr_type type)
  67 {
  68         unsigned long low, high;
  69
  70         if (size == 0) {
  71                 /* Disable */
  72                 high = low = 0;
  73         } else {
  74                 high = base << PAGE_SHIFT;
  75                 if (centaur_mcr_type == 0) {
  76                         /* Only support write-combining... */
  77                         low = -size << PAGE_SHIFT | 0x1f;
  78                 } else {
  79                         if (type == MTRR_TYPE_UNCACHABLE)
  80                                 low = -size << PAGE_SHIFT | 0x02; /* NC */
  81                         else
  82                                 low = -size << PAGE_SHIFT | 0x09; /* WWO, WC */
  83                 }
  84         }
  85         centaur_mcr[reg].high = high;
  86         centaur_mcr[reg].low = low;
  87         wrmsr(MSR_IDT_MCR0 + reg, low, high);
  88 }
  89
  90 static int
  91 centaur_validate_add_page(unsigned long base, unsigned long size, unsigned int type)
  92 {
  93         /*
  94          * FIXME: Winchip2 supports uncached
  95          */
  96         if (type != MTRR_TYPE_WRCOMB &&
  97             (centaur_mcr_type == 0 || type != MTRR_TYPE_UNCACHABLE)) {
  98                 pr_warn("mtrr: only write-combining%s supported\n",
  99                            centaur_mcr_type ? " and uncacheable are" : " is");
 100                 return -EINVAL;
 101         }
 102         return 0;
 103 }
 104
 105 const struct mtrr_ops centaur_mtrr_ops = {
 106         .var_regs          = 8,
 107         .set               = centaur_set_mcr,
 108         .get               = centaur_get_mcr,
 109         .get_free_region   = centaur_get_free_region,
 110         .validate_add_page = centaur_validate_add_page,
 111         .have_wrcomb       = positive_have_wrcomb,
 112 };