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

   1 #include <linux/init.h>
   2 #include <linux/mm.h>
   3 #include <asm/mtrr.h>
   4 #include <asm/msr.h>
   5
   6 #include "mtrr.h"
   7
   8 static void
   9 amd_get_mtrr(unsigned int reg, unsigned long *base,
  10              unsigned long *size, mtrr_type * type)
  11 {
  12         unsigned long low, high;
  13
  14         rdmsr(MSR_K6_UWCCR, low, high);
  15         /*  Upper dword is region 1, lower is region 0  */
  16         if (reg == 1)
  17                 low = high;
  18         /*  The base masks off on the right alignment  */
  19         *base = (low & 0xFFFE0000) >> PAGE_SHIFT;
  20         *type = 0;
  21         if (low & 1)
  22                 *type = MTRR_TYPE_UNCACHABLE;
  23         if (low & 2)
  24                 *type = MTRR_TYPE_WRCOMB;
  25         if (!(low & 3)) {
  26                 *size = 0;
  27                 return;
  28         }
  29         /*
  30          *  This needs a little explaining. The size is stored as an
  31          *  inverted mask of bits of 128K granularity 15 bits long offset
  32          *  2 bits
  33          *
  34          *  So to get a size we do invert the mask and add 1 to the lowest
  35          *  mask bit (4 as its 2 bits in). This gives us a size we then shift
  36          *  to turn into 128K blocks
  37          *
  38          *  eg              111 1111 1111 1100      is 512K
  39          *
  40          *  invert          000 0000 0000 0011
  41          *  +1              000 0000 0000 0100
  42          *  *128K   ...
  43          */
  44         low = (~low) & 0x1FFFC;
  45         *size = (low + 4) << (15 - PAGE_SHIFT);
  46         return;
  47 }
  48
  49 static void amd_set_mtrr(unsigned int reg, unsigned long base,
  50                          unsigned long size, mtrr_type type)
  51 /*  [SUMMARY] Set variable MTRR register on the local CPU.
  52     <reg> The register to set.
  53     <base> The base address of the region.
  54     <size> The size of the region. If this is 0 the region is disabled.
  55     <type> The type of the region.
  56     [RETURNS] Nothing.
  57 */
  58 {
  59         u32 regs[2];
  60
  61         /*
  62          *  Low is MTRR0 , High MTRR 1
  63          */
  64         rdmsr(MSR_K6_UWCCR, regs[0], regs[1]);
  65         /*
  66          *  Blank to disable
  67          */
  68         if (size == 0)
  69                 regs[reg] = 0;
  70         else
  71                 /* Set the register to the base, the type (off by one) and an
  72                    inverted bitmask of the size The size is the only odd
  73                    bit. We are fed say 512K We invert this and we get 111 1111
  74                    1111 1011 but if you subtract one and invert you get the
  75                    desired 111 1111 1111 1100 mask
  76
  77                    But ~(x - 1) == ~x + 1 == -x. Two's complement rocks!  */
  78                 regs[reg] = (-size >> (15 - PAGE_SHIFT) & 0x0001FFFC)
  79                     | (base << PAGE_SHIFT) | (type + 1);
  80
  81         /*
  82          *  The writeback rule is quite specific. See the manual. Its
  83          *  disable local interrupts, write back the cache, set the mtrr
  84          */
  85         wbinvd();
  86         wrmsr(MSR_K6_UWCCR, regs[0], regs[1]);
  87 }
  88
  89 static int amd_validate_add_page(unsigned long base, unsigned long size, unsigned int type)
  90 {
  91         /* Apply the K6 block alignment and size rules
  92            In order
  93            o Uncached or gathering only
  94            o 128K or bigger block
  95            o Power of 2 block
  96            o base suitably aligned to the power
  97         */
  98         if (type > MTRR_TYPE_WRCOMB || size < (1 << (17 - PAGE_SHIFT))
  99             || (size & ~(size - 1)) - size || (base & (size - 1)))
 100                 return -EINVAL;
 101         return 0;
 102 }
 103
 104 static struct mtrr_ops amd_mtrr_ops = {
 105         .vendor            = X86_VENDOR_AMD,
 106         .set               = amd_set_mtrr,
 107         .get               = amd_get_mtrr,
 108         .get_free_region   = generic_get_free_region,
 109         .validate_add_page = amd_validate_add_page,
 110         .have_wrcomb       = positive_have_wrcomb,
 111 };
 112
 113 int __init amd_init_mtrr(void)
 114 {
 115         set_mtrr_ops(&amd_mtrr_ops);
 116         return 0;
 117 }
 118
 119 //arch_initcall(amd_mtrr_init);