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x86: don't disable TSC in any C states on AMD Fam10h

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The ACPI code currently disables TSC use in any C2 and C3
states. But the AMD Fam10h BKDG documents that the TSC
will never stop in any C states when the CONSTANT_TSC bit is
set. Make this disabling conditional on CONSTANT_TSC
not set on AMD.

I actually think this is true on Intel too for C2 states
on CPUs with p-state invariant TSC, but this needs
further discussions with Len to really confirm :-)

So far it is only enabled on AMD.

Cc: lenb@kernel.org

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Andi Kleen 2008-01-30 13:32:41 +01:00 committed by Ingo Molnar
parent 32c7553f82
commit ddb25f9ac1
1 changed files with 28 additions and 4 deletions
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32
drivers/acpi/processor_idle.c
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@ -357,6 +357,26 @@ int acpi_processor_resume(struct acpi_device * device)
return 0;
}
#if defined (CONFIG_GENERIC_TIME) && defined (CONFIG_X86_TSC)
static int tsc_halts_in_c(int state)
{
switch (boot_cpu_data.x86_vendor) {
case X86_VENDOR_AMD:
/*
* AMD Fam10h TSC will tick in all
* C/P/S0/S1 states when this bit is set.
*/
if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
return 0;
/*FALL THROUGH*/
case X86_VENDOR_INTEL:
/* Several cases known where TSC halts in C2 too */
default:
return state > ACPI_STATE_C1;
}
}
#endif
#ifndef CONFIG_CPU_IDLE
static void acpi_processor_idle(void)
{
@ -516,7 +536,8 @@ static void acpi_processor_idle(void)
#if defined (CONFIG_GENERIC_TIME) && defined (CONFIG_X86_TSC)
/* TSC halts in C2, so notify users */
mark_tsc_unstable("possible TSC halt in C2");
if (tsc_halts_in_c(ACPI_STATE_C2))
mark_tsc_unstable("possible TSC halt in C2");
#endif
/* Compute time (ticks) that we were actually asleep */
sleep_ticks = ticks_elapsed(t1, t2);
@ -580,7 +601,8 @@ static void acpi_processor_idle(void)
#if defined (CONFIG_GENERIC_TIME) && defined (CONFIG_X86_TSC)
/* TSC halts in C3, so notify users */
mark_tsc_unstable("TSC halts in C3");
if (tsc_halts_in_c(ACPI_STATE_C3))
mark_tsc_unstable("TSC halts in C3");
#endif
/* Compute time (ticks) that we were actually asleep */
sleep_ticks = ticks_elapsed(t1, t2);
@ -1445,7 +1467,8 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
#if defined (CONFIG_GENERIC_TIME) && defined (CONFIG_X86_TSC)
/* TSC could halt in idle, so notify users */
mark_tsc_unstable("TSC halts in idle");;
if (tsc_halts_in_c(cx->type))
mark_tsc_unstable("TSC halts in idle");;
#endif
sleep_ticks = ticks_elapsed(t1, t2);
@ -1556,7 +1579,8 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
#if defined (CONFIG_GENERIC_TIME) && defined (CONFIG_X86_TSC)
/* TSC could halt in idle, so notify users */
mark_tsc_unstable("TSC halts in idle");
if (tsc_halts_in_c(ACPI_STATE_C3))
mark_tsc_unstable("TSC halts in idle");
#endif
sleep_ticks = ticks_elapsed(t1, t2);
/* Tell the scheduler how much we idled: */