From mboxrd@z Thu Jan 1 00:00:00 1970 From: Venkatesh Pallipadi Subject: [PATCH] acpi: Don't let acpi_pad needlessly mark TSC unstable Date: Tue, 18 May 2010 14:39:16 -0700 Message-ID: <1274218756-31306-1-git-send-email-venki@google.com> Return-path: Received: from smtp-out.google.com ([74.125.121.35]:4070 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754807Ab0ERVjb (ORCPT ); Tue, 18 May 2010 17:39:31 -0400 Received: from kpbe19.cbf.corp.google.com (kpbe19.cbf.corp.google.com [172.25.105.83]) by smtp-out.google.com with ESMTP id o4ILdSaE006318 for ; Tue, 18 May 2010 14:39:29 -0700 Received: from pzk12 (pzk12.prod.google.com [10.243.19.140]) by kpbe19.cbf.corp.google.com with ESMTP id o4ILdRAJ028538 for ; Tue, 18 May 2010 14:39:27 -0700 Received: by pzk12 with SMTP id 12so4106253pzk.9 for ; Tue, 18 May 2010 14:39:27 -0700 (PDT) Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Len Brown Cc: ACPI list , Shaohua Li , Venkatesh Pallipadi 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 --- 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 19dacfd..8ca490b 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, -- 1.7.0.1