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broadwell: Add small delay before Flex Ratio reboot

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In order to prevent possible TPM lockout due to PLTRST assertion
shortly after powering up add a small delay before the reset.
This will affect cold power up only, reboot/resume/warmboot will
all have the flex ratio locked already so this reset is unneeded.

BUG=chrome-os-partner:29859
BRANCH=None
TEST=build and boot on samus.  I tried unsuccessfully to trigger the
TPM lockout, but I was not able to do that consistently without this
patch so it is unknown yet whether this is 100% effective.

Change-Id: Ief8c9261c0268b0f90a3022213ebd2b06633b481
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/211893
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
This commit is contained in:
Duncan Laurie 2014-08-11 13:38:26 -07:00 • committed by chrome-internal-fetch
commit 20413f2eaf
1 changed files with 14 additions and 0 deletions
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14
src/soc/intel/broadwell/bootblock/cpu.c
View file

@ -56,6 +56,17 @@ static void enable_rom_caching(void)
wrmsr(MTRRdefType_MSR, msr);
}
static void bootblock_mdelay(int ms)
{
u32 target = ms * 24 * 1000;
msr_t current;
msr_t start = rdmsr(MSR_COUNTER_24_MHZ);
do {
current = rdmsr(MSR_COUNTER_24_MHZ);
} while ((current.lo - start.lo) < target);
}
static void set_flex_ratio_to_tdp_nominal(void)
{
msr_t flex_ratio, msr;
@ -96,6 +107,9 @@ static void set_flex_ratio_to_tdp_nominal(void)
/* Set soft reset control to use register value */
RCBA32_OR(SOFT_RESET_CTRL, 1);
/* Delay before reset to avoid potential TPM lockout */
bootblock_mdelay(30);
/* Issue warm reset, will be "CPU only" due to soft reset data */
outb(0x0, 0xcf9);
outb(0x6, 0xcf9);