LXR linux/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
   8static void
   9amd_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 */
  58static void
  59amd_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
  94static int
  95amd_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
 111static 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
 120int __init amd_init_mtrr(void)
 121{
 122        set_mtrr_ops(&amd_mtrr_ops);
 123        return 0;
 124}
 125