summaryrefslogtreecommitdiff
path: root/Documentation/power/runtime_pm.rst
diff options
context:
space:
mode:
authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2021-12-07 21:54:32 +0300
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2021-12-17 18:16:40 +0300
commitc24efa6732788f0be22cdf5d2aedd5e3117e983f (patch)
treebe9088b34899b2a67f9b98665a33d8579375bc47 /Documentation/power/runtime_pm.rst
parent1a3c7bb088266fa2db017be299f91f1c1894c857 (diff)
downloadlinux-c24efa6732788f0be22cdf5d2aedd5e3117e983f.tar.xz
PM: runtime: Capture device status before disabling runtime PM
In some cases (for example, during system-wide suspend and resume of devices) it is useful to know whether or not runtime PM has ever been enabled for a given device and, if so, what the runtime PM status of it had been right before runtime PM was disabled for it last time. For this reason, introduce a new struct dev_pm_info field called last_status that will be used for capturing the runtime PM status of the device when its power.disable_depth counter changes from 0 to 1. The new field will be set to RPM_INVALID to start with and whenever power.disable_depth changes from 1 to 0, so it will be valid only when runtime PM of the device is currently disabled, but it has been enabled at least once. Immediately use power.last_status in rpm_resume() to make it handle the case when PM runtime is disabled for the device, but its runtime PM status is RPM_ACTIVE more consistently. Namely, make it return 1 if power.last_status is also equal to RPM_ACTIVE in that case (the idea being that if the status was RPM_ACTIVE last time when power.disable_depth was changing from 0 to 1 and it is still RPM_ACTIVE, it can be assumed to reflect what happened to the device last time when it was using runtime PM) and -EACCES otherwise. Update the documentation to provide a description of last_status and change the description of pm_runtime_resume() in it to reflect the new behavior of rpm_active(). While at it, rearrange the code in pm_runtime_enable() to be more straightforward and replace the WARN() macro in it with a pr_warn() invocation which is less disruptive. Link: https://lore.kernel.org/linux-pm/20211026222626.39222-1-ulf.hansson@linaro.org/t/#u Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'Documentation/power/runtime_pm.rst')
-rw-r--r--Documentation/power/runtime_pm.rst14
1 files changed, 10 insertions, 4 deletions
diff --git a/Documentation/power/runtime_pm.rst b/Documentation/power/runtime_pm.rst
index d6bf84f061f4..65b86e487afe 100644
--- a/Documentation/power/runtime_pm.rst
+++ b/Documentation/power/runtime_pm.rst
@@ -265,6 +265,10 @@ defined in include/linux/pm.h:
RPM_SUSPENDED, which means that each device is initially regarded by the
PM core as 'suspended', regardless of its real hardware status
+ `enum rpm_status last_status;`
+ - the last runtime PM status of the device captured before disabling runtime
+ PM for it (invalid initially and when disable_depth is 0)
+
`unsigned int runtime_auto;`
- if set, indicates that the user space has allowed the device driver to
power manage the device at run time via the /sys/devices/.../power/control
@@ -333,10 +337,12 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
`int pm_runtime_resume(struct device *dev);`
- execute the subsystem-level resume callback for the device; returns 0 on
- success, 1 if the device's runtime PM status was already 'active' or
- error code on failure, where -EAGAIN means it may be safe to attempt to
- resume the device again in future, but 'power.runtime_error' should be
- checked additionally, and -EACCES means that 'power.disable_depth' is
+ success, 1 if the device's runtime PM status is already 'active' (also if
+ 'power.disable_depth' is nonzero, but the status was 'active' when it was
+ changing from 0 to 1) or error code on failure, where -EAGAIN means it may
+ be safe to attempt to resume the device again in future, but
+ 'power.runtime_error' should be checked additionally, and -EACCES means
+ that the callback could not be run, because 'power.disable_depth' was
different from 0
`int pm_runtime_resume_and_get(struct device *dev);`