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#include <linux/init.h>
#include <linux/mm.h>
#include <asm/mtrr.h>
#include <asm/msr.h>
#include "mtrr.h"
static void
amd_get_mtrr(unsigned int reg, unsigned long *base,
unsigned long *size, mtrr_type *type)
{
unsigned long low, high;
rdmsr(MSR_K6_UWCCR, low, high);
/* Upper dword is region 1, lower is region 0 */
if (reg == 1)
low = high;
/* The base masks off on the right alignment */
*base = (low & 0xFFFE0000) >> PAGE_SHIFT;
*type = 0;
if (low & 1)
*type = MTRR_TYPE_UNCACHABLE;
if (low & 2)
*type = MTRR_TYPE_WRCOMB;
if (!(low & 3)) {
*size = 0;
return;
}
/*
* This needs a little explaining. The size is stored as an
* inverted mask of bits of 128K granularity 15 bits long offset
* 2 bits.
*
* So to get a size we do invert the mask and add 1 to the lowest
* mask bit (4 as its 2 bits in). This gives us a size we then shift
* to turn into 128K blocks.
*
* eg 111 1111 1111 1100 is 512K
*
* invert 000 0000 0000 0011
* +1 000 0000 0000 0100
* *128K ...
*/
low = (~low) & 0x1FFFC;
*size = (low + 4) << (15 - PAGE_SHIFT);
}
/**
* amd_set_mtrr - Set variable MTRR register on the local CPU.
*
* @reg The register to set.
* @base The base address of the region.
* @size The size of the region. If this is 0 the region is disabled.
* @type The type of the region.
*
* Returns nothing.
*/
static void
amd_set_mtrr(unsigned int reg, unsigned long base, unsigned long size, mtrr_type type)
{
u32 regs[2];
/*
* Low is MTRR0, High MTRR 1
*/
rdmsr(MSR_K6_UWCCR, regs[0], regs[1]);
/*
* Blank to disable
*/
if (size == 0) {
regs[reg] = 0;
} else {
/*
* Set the register to the base, the type (off by one) and an
* inverted bitmask of the size The size is the only odd
* bit. We are fed say 512K We invert this and we get 111 1111
* 1111 1011 but if you subtract one and invert you get the
* desired 111 1111 1111 1100 mask
*
* But ~(x - 1) == ~x + 1 == -x. Two's complement rocks!
*/
regs[reg] = (-size >> (15 - PAGE_SHIFT) & 0x0001FFFC)
| (base << PAGE_SHIFT) | (type + 1);
}
/*
* The writeback rule is quite specific. See the manual. Its
* disable local interrupts, write back the cache, set the mtrr
*/
wbinvd();
wrmsr(MSR_K6_UWCCR, regs[0], regs[1]);
}
static int
amd_validate_add_page(unsigned long base, unsigned long size, unsigned int type)
{
/*
* Apply the K6 block alignment and size rules
* In order
* o Uncached or gathering only
* o 128K or bigger block
* o Power of 2 block
* o base suitably aligned to the power
*/
if (type > MTRR_TYPE_WRCOMB || size < (1 << (17 - PAGE_SHIFT))
|| (size & ~(size - 1)) - size || (base & (size - 1)))
return -EINVAL;
return 0;
}
static const struct mtrr_ops amd_mtrr_ops = {
.vendor = X86_VENDOR_AMD,
.set = amd_set_mtrr,
.get = amd_get_mtrr,
.get_free_region = generic_get_free_region,
.validate_add_page = amd_validate_add_page,
.have_wrcomb = positive_have_wrcomb,
};
int __init amd_init_mtrr(void)
{
set_mtrr_ops(&amd_mtrr_ops);
return 0;
}
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