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Subject[tip:x86/cpu] Documentation/ABI: Document umwait control sysfs interfaces
Commit-ID:  203dffacf592317e54480704f569a09f8b7ca380
Gitweb: https://git.kernel.org/tip/203dffacf592317e54480704f569a09f8b7ca380
Author: Fenghua Yu <fenghua.yu@intel.com>
AuthorDate: Wed, 19 Jun 2019 18:33:58 -0700
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Mon, 24 Jun 2019 01:44:35 +0200

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
---
Documentation/ABI/testing/sysfs-devices-system-cpu | 23 ++++++++++++++++++++++
1 file changed, 23 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index 1528239f69b2..923fe2001472 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -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.
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