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Documentation/ABI: Document umwait control sysfs interfaces 

Since two new sysfs interface files are created for umwait control, add
an ABI document entry for the files:

   /sys/devices/system/cpu/umwait_control/enable_c02
   /sys/devices/system/cpu/umwait_control/max_time

[ tglx: Made the write value instructions readable ]

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ashok Raj <ashok.raj@intel.com>
Cc: "Borislav Petkov" <bp@alien8.de>
Cc: "H Peter Anvin" <hpa@zytor.com>
Cc: "Andy Lutomirski" <luto@kernel.org>
Cc: "Peter Zijlstra" <peterz@infradead.org>
Cc: "Tony Luck" <tony.luck@intel.com>
Cc: "Ravi V Shankar" <ravi.v.shankar@intel.com>
Link: https://lkml.kernel.org/r/1560994438-235698-6-git-send-email-fenghua.yu@intel.com
This commit is contained in:
Fenghua Yu 2019-06-19 18:33:58 -07:00 committed by Thomas Gleixner
parent bd9a0c97e5
commit 203dffacf5
1 changed files with 23 additions and 0 deletions
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Documentation/ABI/testing/sysfs-devices-system-cpu
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@ -538,3 +538,26 @@ Description: Intel Energy and Performance Bias Hint (EPB)
This attribute is present for all online CPUs supporting the
Intel EPB feature.
What: /sys/devices/system/cpu/umwait_control
/sys/devices/system/cpu/umwait_control/enable_c02
/sys/devices/system/cpu/umwait_control/max_time
Date: May 2019
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Description: Umwait control
enable_c02: Read/write interface to control umwait C0.2 state
Read returns C0.2 state status:
0: C0.2 is disabled
1: C0.2 is enabled
Write 'y' or '1' or 'on' to enable C0.2 state.
Write 'n' or '0' or 'off' to disable C0.2 state.
The interface is case insensitive.
max_time: Read/write interface to control umwait maximum time
in TSC-quanta that the CPU can reside in either C0.1
or C0.2 state. The time is an unsigned 32-bit number.
Note that a value of zero means there is no limit.
Low order two bits must be zero.