diff options
| author | Venkatesh Pallipadi <venki@google.com> | 2010-05-18 14:39:16 -0700 |
|---|---|---|
| committer | Len Brown <len.brown@intel.com> | 2010-05-28 15:34:57 -0400 |
| commit | 0dc698b93f3eecdda43b22232131324eb41e510c (patch) | |
| tree | 5eff6780615220931c8d86f9ce7f337dd4443904 /drivers/acpi/acpi_pad.c | |
| parent | b6fecaa8685a9922d11db2cd79e76f43c3edc970 (diff) | |
| download | lwn-0dc698b93f3eecdda43b22232131324eb41e510c.tar.gz lwn-0dc698b93f3eecdda43b22232131324eb41e510c.zip | |
ACPI: Don't let acpi_pad needlessly mark TSC unstable
acpi pad driver kind of aggressively marks TSC as unstable at init
time, on mwait capable and non X86_FEATURE_NONSTOP_TSC systems. This is
irrespective of whether pad driver is ever going to be used on the
system or deep C-states are supported/used. This will affect every user
who just happens to compile in (or get a kernel version which
compiles in) acpi pad driver.
Move mark_tsc_unstable() out of init to the actual idle invocation path
of the pad driver.
There is also another bug/missing_feature in the code that it does not
support 'always running apic timer' and switches to broadcast mode
unconditionally. Shaohua, can you take a look at that please.
Signed-off-by: Venkatesh Pallipadi <venki@google.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Diffstat (limited to 'drivers/acpi/acpi_pad.c')
| -rw-r--r-- | drivers/acpi/acpi_pad.c | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/drivers/acpi/acpi_pad.c b/drivers/acpi/acpi_pad.c index 62122134693b..f169e516a1af 100644 --- a/drivers/acpi/acpi_pad.c +++ b/drivers/acpi/acpi_pad.c @@ -43,6 +43,10 @@ static DEFINE_MUTEX(isolated_cpus_lock); #define CPUID5_ECX_EXTENSIONS_SUPPORTED (0x1) #define CPUID5_ECX_INTERRUPT_BREAK (0x2) static unsigned long power_saving_mwait_eax; + +static unsigned char tsc_detected_unstable; +static unsigned char tsc_marked_unstable; + static void power_saving_mwait_init(void) { unsigned int eax, ebx, ecx, edx; @@ -87,8 +91,8 @@ static void power_saving_mwait_init(void) /*FALL THROUGH*/ default: - /* TSC could halt in idle, so notify users */ - mark_tsc_unstable("TSC halts in idle"); + /* TSC could halt in idle */ + tsc_detected_unstable = 1; } #endif } @@ -178,6 +182,11 @@ static int power_saving_thread(void *data) expire_time = jiffies + HZ * (100 - idle_pct) / 100; while (!need_resched()) { + if (tsc_detected_unstable && !tsc_marked_unstable) { + /* TSC could halt in idle, so notify users */ + mark_tsc_unstable("TSC halts in idle"); + tsc_marked_unstable = 1; + } local_irq_disable(); cpu = smp_processor_id(); clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, |