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Message-id: <1387549495-809-6-git-send-email-l.majewski@samsung.com> Date: Fri, 20 Dec 2013 15:24:53 +0100 From: Lukasz Majewski <l.majewski@...sung.com> To: Viresh Kumar <viresh.kumar@...aro.org>, "Rafael J. Wysocki" <rjw@...ysocki.net>, Eduardo Valentin <eduardo.valentin@...com> Cc: "cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>, Linux PM list <linux-pm@...r.kernel.org>, Jonghwa Lee <jonghwa3.lee@...sung.com>, Lukasz Majewski <l.majewski@...sung.com>, Lukasz Majewski <l.majewski@...ess.pl>, linux-kernel <linux-kernel@...r.kernel.org>, Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>, Myungjoo Ham <myungjoo.ham@...sung.com>, durgadoss.r@...el.com, Zhang Rui <rui.zhang@...el.com>, linux-samsung-soc@...r.kernel.org Subject: [PATCH v12 5/7] Documentation:cpufreq:boost: Update BOOST documentation Since the support for software and hardware controlled boosting has been added, the corresponding Documentation entry had been updated. Signed-off-by: Lukasz Majewski <l.majewski@...sung.com> Signed-off-by: Myungjoo Ham <myungjoo.ham@...sung.com> Acked-by: Viresh Kumar <viresh.kumar@...aro.org> --- Changes for v12: - None Changes for v11: - None Changes for v10: - None Changes for v9: - None Changes for v8: - None Changes for v7: - None 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. AMD legacy cpb switch -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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