Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756692Ab3GYQei (ORCPT ); Thu, 25 Jul 2013 12:34:38 -0400 Received: from mailout2.samsung.com ([203.254.224.25]:58629 "EHLO mailout2.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756602Ab3GYQec (ORCPT ); Thu, 25 Jul 2013 12:34:32 -0400 X-AuditID: cbfee61a-b7f196d000007dfa-ad-51f153962fc8 From: Lukasz Majewski To: Viresh Kumar , "Rafael J. Wysocki" , Zhang Rui , Eduardo Valentin Cc: "cpufreq@vger.kernel.org" , Linux PM list , Jonghwa Lee , Lukasz Majewski , Lukasz Majewski , linux-kernel , Bartlomiej Zolnierkiewicz , Daniel Lezcano , Kukjin Kim , Myungjoo Ham , durgadoss.r@intel.com Subject: [PATCH v6 7/8] Documentation:cpufreq:boost: Update BOOST documentation Date: Thu, 25 Jul 2013 18:33:30 +0200 Message-id: <1374770011-22171-8-git-send-email-l.majewski@samsung.com> X-Mailer: git-send-email 1.7.10 In-reply-to: <1374770011-22171-1-git-send-email-l.majewski@samsung.com> References: <1370502472-7249-1-git-send-email-l.majewski@samsung.com> <1374770011-22171-1-git-send-email-l.majewski@samsung.com> X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFjrCLMWRmVeSWpSXmKPExsVy+t9jQd3pwR8DDbb9ZrPYOGM9q8XTph/s FvM+y1r0/bzCbLFm/08mi86zT5gtehdcZbN484jb4s3DzYwWl3fNYbP43HuE0eJ24wo2i/6F vUwWTx72Ac346uHA77F4z0smjzvX9rB5rJv2ltmjb8sqRo9Hi1sYPY7f2M7k8XmTXAB7FJdN SmpOZllqkb5dAlfGv53nWQpmSlS83fGXvYHxs3AXIyeHhICJxNMzkxghbDGJC/fWs3UxcnEI CUxnlNj95R87hNPFJLHr9WGwKjYBPYnPd58ygdgiAnMYJe4cdQcpYhZ4wCyx+PsXoCIODmEB f4n9C+VAalgEVCU+vW0G6+UVcJNYe3sK1DZ5iaf3+9hAbE4Bd4kJk0HiIMuaGCX+3bjLPIGR dwEjwypG0dSC5ILipPRcQ73ixNzi0rx0veT83E2M4LB9JrWDcWWDxSFGAQ5GJR5eBaePgUKs iWXFlbmHGCU4mJVEeM0tgUK8KYmVValF+fFFpTmpxYcYpTlYlMR5D7RaBwoJpCeWpGanphak FsFkmTg4pRoYO5PmPcw4cGNDqNwaA5PEkB4Gtj3P1TZKMS9stm7xyzrtM0H6cns387seTc63 W86nyMl32DrttuZ5ffj3t2lhJhst7zk7mSrI+PD5zfF682gHS/vGihsmZSszPl+pdf6zgcl2 habr5cYDsRJSSaa/O79JSB+XDc+yv7X6XoNMktKew++ddkUqsRRnJBpqMRcVJwIANnaxLFcC AAA= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3272 Lines: 75 Since the support for software and hardware controlled boosting has been added, the corresponding Documentation entry had been updated. Signed-off-by: Lukasz Majewski Signed-off-by: Myungjoo Ham --- Changes for v6: - None Changes for v5: - New patch Documentation/cpu-freq/boost.txt | 26 +++++++++++++------------- 1 file changed, 13 insertions(+), 13 deletions(-) diff --git a/Documentation/cpu-freq/boost.txt b/Documentation/cpu-freq/boost.txt index 9b4edfc..dd62e13 100644 --- a/Documentation/cpu-freq/boost.txt +++ b/Documentation/cpu-freq/boost.txt @@ -17,8 +17,8 @@ Introduction Some CPUs support a functionality to raise the operating frequency of some cores in a multi-core package if certain conditions apply, mostly if the whole chip is not fully utilized and below it's intended thermal -budget. This is done without operating system control by a combination -of hardware and firmware. +budget. The decision about boost disable/enable is made either at hardware +(e.g. x86) or software (e.g ARM). On Intel CPUs this is called "Turbo Boost", AMD calls it "Turbo-Core", in technical documentation "Core performance boost". In Linux we use the term "boost" for convenience. @@ -48,24 +48,24 @@ be desirable: User controlled switch ---------------------- -To allow the user to toggle the boosting functionality, the acpi-cpufreq -driver exports a sysfs knob to disable it. There is a file: +To allow the user to toggle the boosting functionality, the cpufreq core +driver exports a sysfs knob to enable or disable it. There is a file: /sys/devices/system/cpu/cpufreq/boost which can either read "0" (boosting disabled) or "1" (boosting enabled). -Reading the file is always supported, even if the processor does not -support boosting. In this case the file will be read-only and always -reads as "0". Explicitly changing the permissions and writing to that -file anyway will return EINVAL. +The file is exported only when cpufreq driver supports boosting. +Explicitly changing the permissions and writing to that file anyway will +return EINVAL. On supported CPUs one can write either a "0" or a "1" into this file. This will either disable the boost functionality on all cores in the -whole system (0) or will allow the hardware to boost at will (1). +whole system (0) or will allow the software or hardware to boost at will +(1). Writing a "1" does not explicitly boost the system, but just allows the -CPU (and the firmware) to boost at their discretion. Some implementations -take external factors like the chip's temperature into account, so -boosting once does not necessarily mean that it will occur every time -even using the exact same software setup. +CPU to boost at their discretion. Some implementations take external +factors like the chip's temperature into account, so boosting once does +not necessarily mean that it will occur every time even using the exact +same software setup. 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