Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932533Ab0G3Rp2 (ORCPT ); Fri, 30 Jul 2010 13:45:28 -0400 Received: from kroah.org ([198.145.64.141]:36116 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932428Ab0G3Rfx (ORCPT ); Fri, 30 Jul 2010 13:35:53 -0400 X-Mailbox-Line: From gregkh@clark.site Fri Jul 30 10:31:13 2010 Message-Id: <20100730173113.093448975@clark.site> User-Agent: quilt/0.48-11.2 Date: Fri, 30 Jul 2010 10:31:20 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Len Brown Subject: [115/140] ACPI: skip checking BM_STS if the BIOS doesnt ask for it In-Reply-To: <20100730173205.GA22581@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2837 Lines: 88 2.6.33-stable review patch. If anyone has any objections, please let us know. ------------------ From: Len Brown commit 718be4aaf3613cf7c2d097f925abc3d3553c0605 upstream. It turns out that there is a bit in the _CST for Intel FFH C3 that tells the OS if we should be checking BM_STS or not. Linux has been unconditionally checking BM_STS. If the chip-set is configured to enable BM_STS, it can retard or completely prevent entry into deep C-states -- as illustrated by turbostat: http://userweb.kernel.org/~lenb/acpi/utils/pmtools/turbostat/ ref: Intel Processor Vendor-Specific ACPI Interface Specification table 4 "_CST FFH GAS Field Encoding" Bit 1: Set to 1 if OSPM should use Bus Master avoidance for this C-state https://bugzilla.kernel.org/show_bug.cgi?id=15886 Signed-off-by: Len Brown Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/acpi/cstate.c | 9 +++++++++ drivers/acpi/processor_idle.c | 2 +- include/acpi/processor.h | 3 ++- 3 files changed, 12 insertions(+), 2 deletions(-) --- a/arch/x86/kernel/acpi/cstate.c +++ b/arch/x86/kernel/acpi/cstate.c @@ -145,6 +145,15 @@ int acpi_processor_ffh_cstate_probe(unsi percpu_entry->states[cx->index].eax = cx->address; percpu_entry->states[cx->index].ecx = MWAIT_ECX_INTERRUPT_BREAK; } + + /* + * For _CST FFH on Intel, if GAS.access_size bit 1 is cleared, + * then we should skip checking BM_STS for this C-state. + * ref: "Intel Processor Vendor-Specific ACPI Interface Specification" + */ + if ((c->x86_vendor == X86_VENDOR_INTEL) && !(reg->access_size & 0x2)) + cx->bm_sts_skip = 1; + return retval; } EXPORT_SYMBOL_GPL(acpi_processor_ffh_cstate_probe); --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -954,7 +954,7 @@ static int acpi_idle_enter_bm(struct cpu if (acpi_idle_suspend) return(acpi_idle_enter_c1(dev, state)); - if (acpi_idle_bm_check()) { + if (!cx->bm_sts_skip && acpi_idle_bm_check()) { if (dev->safe_state) { dev->last_state = dev->safe_state; return dev->safe_state->enter(dev, dev->safe_state); --- a/include/acpi/processor.h +++ b/include/acpi/processor.h @@ -48,7 +48,7 @@ struct acpi_power_register { u8 space_id; u8 bit_width; u8 bit_offset; - u8 reserved; + u8 access_size; u64 address; } __attribute__ ((packed)); @@ -74,6 +74,7 @@ struct acpi_processor_cx { u32 power; u32 usage; u64 time; + u8 bm_sts_skip; struct acpi_processor_cx_policy promotion; struct acpi_processor_cx_policy demotion; char desc[ACPI_CX_DESC_LEN]; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/