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x86: Add a function to set variable MTRRs

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Normally U-Boot handles MTRRs through an add/commit process which
overwrites all MTRRs. But in very early boot it is not desirable to clear
the existing MTRRs since they may be in use and it can cause a hang.

Add a new mtrr_set_next_var() function which sets up the next available
MTRR to the required region.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
[bmeng: pass 'type' to set_var_mtrr() in mtrr_set_next_var()]
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
This commit is contained in:
Simon Glass 2019-09-25 08:56:46 -06:00 committed by Bin Meng
parent 6ccb2f890b
commit add3f4c918
2 changed files with 50 additions and 0 deletions
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38
arch/x86/cpu/mtrr.c
View File

@ -112,3 +112,41 @@ int mtrr_add_request(int type, uint64_t start, uint64_t size)
return 0;
}
static int get_var_mtrr_count(void)
{
return msr_read(MSR_MTRR_CAP_MSR).lo & MSR_MTRR_CAP_VCNT;
}
static int get_free_var_mtrr(void)
{
struct msr_t maskm;
int vcnt;
int i;
vcnt = get_var_mtrr_count();
/* Identify the first var mtrr which is not valid */
for (i = 0; i < vcnt; i++) {
maskm = msr_read(MTRR_PHYS_MASK_MSR(i));
if ((maskm.lo & MTRR_PHYS_MASK_VALID) == 0)
return i;
}
/* No free var mtrr */
return -ENOSPC;
}
int mtrr_set_next_var(uint type, uint64_t start, uint64_t size)
{
int mtrr;
mtrr = get_free_var_mtrr();
if (mtrr < 0)
return mtrr;
set_var_mtrr(mtrr, type, start, size);
debug("MTRR %x: start=%x, size=%x\n", mtrr, (uint)start, (uint)size);
return 0;
}

12
arch/x86/include/asm/mtrr.h
View File

@ -117,6 +117,18 @@ int mtrr_add_request(int type, uint64_t start, uint64_t size);
*/
int mtrr_commit(bool do_caches);
/**
* mtrr_set_next_var() - set up a variable MTRR
*
* This finds the first free variable MTRR and sets to the given area
*
* @type: Requested type (MTRR_TYPE_)
* @start: Start address
* @size: Size
* @return 0 on success, -ENOSPC if there are no more MTRRs
*/
int mtrr_set_next_var(uint type, uint64_t base, uint64_t size);
#endif
#if ((CONFIG_XIP_ROM_SIZE & (CONFIG_XIP_ROM_SIZE - 1)) != 0)