Messages in this thread Patch in this message | | | From | Andi Kleen <> | Subject | [PATCH] [18/20] x86: Don't disable TSC in any C states on AMD Fam10h | Date | Thu, 3 Jan 2008 01:50:14 +0100 (CET) |
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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>
--- drivers/acpi/processor_idle.c | 32 ++++++++++++++++++++++++++++---- 1 file changed, 28 insertions(+), 4 deletions(-)
Index: linux/drivers/acpi/processor_idle.c =================================================================== --- linux.orig/drivers/acpi/processor_idle.c +++ linux/drivers/acpi/processor_idle.c @@ -353,6 +353,26 @@ int acpi_processor_resume(struct acpi_de 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) { @@ -512,7 +532,8 @@ 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); @@ -576,7 +597,8 @@ 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); @@ -1441,7 +1463,8 @@ static int acpi_idle_enter_simple(struct #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); @@ -1552,7 +1575,8 @@ static int acpi_idle_enter_bm(struct cpu #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: */
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