From ddb25f9ac1c4b4f9ba0bdacd7850a921a0c6886c Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Wed, 30 Jan 2008 13:32:41 +0100 Subject: x86: don't disable TSC in any C states on AMD Fam10h 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 Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner --- drivers/acpi/processor_idle.c | 32 ++++++++++++++++++++++++++++---- 1 file changed, 28 insertions(+), 4 deletions(-) diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index 0721a8183c8..eb1f82f7915 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -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: */ -- cgit v1.2.3