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-rw-r--r--Documentation/ABI/testing/sysfs-devices-system-cpu23
1 files changed, 23 insertions, 0 deletions
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.