Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753455Ab1DAF7M (ORCPT ); Fri, 1 Apr 2011 01:59:12 -0400 Received: from vms173005pub.verizon.net ([206.46.173.5]:36474 "EHLO vms173005pub.verizon.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752274Ab1DAF7K (ORCPT ); Fri, 1 Apr 2011 01:59:10 -0400 Date: Fri, 01 Apr 2011 01:59:01 -0400 (EDT) From: Len Brown X-X-Sender: lenb@x980 To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, linux-pm@lists.linux-foundation.org Subject: [PATCH 2.6.39 & -stable] x86 intel power: Initialize MSR_IA32_ENERGY_PERF_BIAS Message-id: User-Agent: Alpine 2.02 (LFD 1266 2009-07-14) MIME-version: 1.0 Content-type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2652 Lines: 75 From: Len Brown Since 2.6.36 (23016bf0d25), Linux prints the existence of "epb" in /proc/cpuinfo, Since 2.6.38 (d5532ee7b40), the x86_energy_perf_policy(8) utility has been available in-tree to update MSR_IA32_ENERGY_PERF_BIAS. However, the typical BIOS fails to initialize the MSR, presumably because this is handled by high-volume shrink-wrap operating systems... Linux distros, on the other hand, do not yet invoke x86_energy_perf_policy(8). As a result, WSM-EP, SNB, and later hardware from Intel will run in its default hardware power-on state (performance), which assumes that users care for performance at all costs and not for energy efficiency. While that is fine for performance benchmarks, the hardware's intended default operating point is "normal" mode... Initialize the MSR to the "normal" by default during kernel boot. x86_energy_perf_policy(8) is available to change the default after boot, should the user have a different preference. cc: stable@kernel.org Signed-off-by: Len Brown --- arch/x86/include/asm/msr-index.h | 3 +++ arch/x86/kernel/cpu/intel.c | 14 ++++++++++++++ 2 files changed, 17 insertions(+), 0 deletions(-) diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h index 43a18c7..91fedd9 100644 --- a/arch/x86/include/asm/msr-index.h +++ b/arch/x86/include/asm/msr-index.h @@ -250,6 +250,9 @@ #define MSR_IA32_TEMPERATURE_TARGET 0x000001a2 #define MSR_IA32_ENERGY_PERF_BIAS 0x000001b0 +#define ENERGY_PERF_BIAS_PERFORMANCE 0 +#define ENERGY_PERF_BIAS_NORMAL 6 +#define ENERGY_PERF_BIAS_POWERSWAVE 15 #define MSR_IA32_PACKAGE_THERM_STATUS 0x000001b1 diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index d16c2c5..48cca4a 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -448,6 +448,20 @@ static void __cpuinit init_intel(struct cpuinfo_x86 *c) if (cpu_has(c, X86_FEATURE_VMX)) detect_vmx_virtcap(c); + + /* + * Initialize MSR_IA32_ENERGY_PERF_BIAS if BIOS did not. + * x86_energy_perf_policy(8) is available to change it at run-time + */ + if (cpu_has(c, X86_FEATURE_EPB)) { + u64 epb; + + rdmsrl(MSR_IA32_ENERGY_PERF_BIAS, epb); + if ((epb & 0xF) == 0) { + epb = (epb & ~0xF) | ENERGY_PERF_BIAS_NORMAL; + wrmsrl(MSR_IA32_ENERGY_PERF_BIAS, epb); + } + } } #ifdef CONFIG_X86_32 -- 1.7.4.2.406.gbe91 -- 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/