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 }
  47
  48 /**
  49  * amd_set_mtrr - Set variable MTRR register on the local CPU.
  50  *
  51  * @reg The register to set.
  52  * @base The base address of the region.
  53  * @size The size of the region. If this is 0 the region is disabled.
  54  * @type The type of the region.
  55  *
  56  * Returns nothing.
  57  */
  58 static void
  59 amd_set_mtrr(unsigned int reg, unsigned long base, unsigned long size, mtrr_type type)
  60 {
  61         u32 regs[2];
  62
  63         /*
  64          * Low is MTRR0, High MTRR 1
  65          */
  66         rdmsr(MSR_K6_UWCCR, regs[0], regs[1]);
  67         /*
  68          * Blank to disable
  69          */
  70         if (size == 0) {
  71                 regs[reg] = 0;
  72         } else {
  73                 /*
  74                  * Set the register to the base, the type (off by one) and an
  75                  * inverted bitmask of the size The size is the only odd
  76                  * bit. We are fed say 512K We invert this and we get 111 1111
  77                  * 1111 1011 but if you subtract one and invert you get the
  78                  * desired 111 1111 1111 1100 mask
  79                  *
  80                  *  But ~(x - 1) == ~x + 1 == -x. Two's complement rocks!
  81                  */
  82                 regs[reg] = (-size >> (15 - PAGE_SHIFT) & 0x0001FFFC)
  83                     | (base << PAGE_SHIFT) | (type + 1);
  84         }
  85
  86         /*
  87          * The writeback rule is quite specific. See the manual. Its
  88          * disable local interrupts, write back the cache, set the mtrr
  89          */
  90         wbinvd();
  91         wrmsr(MSR_K6_UWCCR, regs[0], regs[1]);
  92 }
  93
  94 static int
  95 amd_validate_add_page(unsigned long base, unsigned long size, unsigned int type)
  96 {
  97         /*
  98          * Apply the K6 block alignment and size rules
  99          * In order
 100          * o Uncached or gathering only
 101          * o 128K or bigger block
 102          * o Power of 2 block
 103          * o base suitably aligned to the power
 104          */
 105         if (type > MTRR_TYPE_WRCOMB || size < (1 << (17 - PAGE_SHIFT))
 106             || (size & ~(size - 1)) - size || (base & (size - 1)))
 107                 return -EINVAL;
 108         return 0;
 109 }
 110
 111 static const struct mtrr_ops amd_mtrr_ops = {
 112         .vendor            = X86_VENDOR_AMD,
 113         .set               = amd_set_mtrr,
 114         .get               = amd_get_mtrr,
 115         .get_free_region   = generic_get_free_region,
 116         .validate_add_page = amd_validate_add_page,
 117         .have_wrcomb       = positive_have_wrcomb,
 118 };
 119
 120 int __init amd_init_mtrr(void)
 121 {
 122         set_mtrr_ops(&amd_mtrr_ops);
 123         return 0;
 124 }