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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2017-11-07 11:33:49 +0100
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2017-11-08 12:14:51 +0100
commit0759e80b84e34a84e7e46e2b1adb528c83d84a47 (patch)
treeffd28668a079d909242da53cdd4cc71855a0bb3e /Documentation/ABI
parent31f18230e480d6224e71910e9ab43a097d811fb0 (diff)
downloadlinux-0759e80b84e34a84e7e46e2b1adb528c83d84a47.tar.bz2
PM / QoS: Fix device resume latency framework
The special value of 0 for device resume latency PM QoS means "no restriction", but there are two problems with that. First, device resume latency PM QoS requests with 0 as the value are always put in front of requests with positive values in the priority lists used internally by the PM QoS framework, causing 0 to be chosen as an effective constraint value. However, that 0 is then interpreted as "no restriction" effectively overriding the other requests with specific restrictions which is incorrect. Second, the users of device resume latency PM QoS have no way to specify that *any* resume latency at all should be avoided, which is an artificial limitation in general. To address these issues, modify device resume latency PM QoS to use S32_MAX as the "no constraint" value and 0 as the "no latency at all" one and rework its users (the cpuidle menu governor, the genpd QoS governor and the runtime PM framework) to follow these changes. Also add a special "n/a" value to the corresponding user space I/F to allow user space to indicate that it cannot accept any resume latencies at all for the given device. Fixes: 85dc0b8a4019 (PM / QoS: Make it possible to expose PM QoS latency constraints) Link: https://bugzilla.kernel.org/show_bug.cgi?id=197323 Reported-by: Reinette Chatre <reinette.chatre@intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Tested-by: Reinette Chatre <reinette.chatre@intel.com> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be> Tested-by: Tero Kristo <t-kristo@ti.com> Reviewed-by: Ramesh Thomas <ramesh.thomas@intel.com>
Diffstat (limited to 'Documentation/ABI')
-rw-r--r--Documentation/ABI/testing/sysfs-devices-power4
1 files changed, 3 insertions, 1 deletions
diff --git a/Documentation/ABI/testing/sysfs-devices-power b/Documentation/ABI/testing/sysfs-devices-power
index f4b24c327665..80a00f7b6667 100644
--- a/Documentation/ABI/testing/sysfs-devices-power
+++ b/Documentation/ABI/testing/sysfs-devices-power
@@ -211,7 +211,9 @@ Description:
device, after it has been suspended at run time, from a resume
request to the moment the device will be ready to process I/O,
in microseconds. If it is equal to 0, however, this means that
- the PM QoS resume latency may be arbitrary.
+ the PM QoS resume latency may be arbitrary and the special value
+ "n/a" means that user space cannot accept any resume latency at
+ all for the given device.
Not all drivers support this attribute. If it isn't supported,
it is not present.