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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>
This commit is contained in:
Rafael J. Wysocki 2021-12-07 19:54:32 +01:00
parent 1a3c7bb088
commit c24efa6732
3 changed files with 37 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
Documentation/power/runtime_pm.rst
View File

@ -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);`

45
drivers/base/power/runtime.c
View File

@ -742,13 +742,15 @@ static int rpm_resume(struct device *dev, int rpmflags)
trace_rpm_resume_rcuidle(dev, rpmflags);
repeat:
if (dev->power.runtime_error)
if (dev->power.runtime_error) {
retval = -EINVAL;
else if (dev->power.disable_depth == 1 && dev->power.is_suspended
&& dev->power.runtime_status == RPM_ACTIVE)
retval = 1;
else if (dev->power.disable_depth > 0)
retval = -EACCES;
} else if (dev->power.disable_depth > 0) {
if (dev->power.runtime_status == RPM_ACTIVE &&
dev->power.last_status == RPM_ACTIVE)
retval = 1;
else
retval = -EACCES;
}
if (retval)
goto out;
@ -1410,8 +1412,10 @@ void __pm_runtime_disable(struct device *dev, bool check_resume)
/* Update time accounting before disabling PM-runtime. */
update_pm_runtime_accounting(dev);
if (!dev->power.disable_depth++)
if (!dev->power.disable_depth++) {
__pm_runtime_barrier(dev);
dev->power.last_status = dev->power.runtime_status;
}
out:
spin_unlock_irq(&dev->power.lock);
@ -1428,23 +1432,23 @@ void pm_runtime_enable(struct device *dev)
spin_lock_irqsave(&dev->power.lock, flags);
if (dev->power.disable_depth > 0) {
dev->power.disable_depth--;
/* About to enable runtime pm, set accounting_timestamp to now */
if (!dev->power.disable_depth)
dev->power.accounting_timestamp = ktime_get_mono_fast_ns();
} else {
if (!dev->power.disable_depth) {
dev_warn(dev, "Unbalanced %s!\n", __func__);
goto out;
}
WARN(!dev->power.disable_depth &&
dev->power.runtime_status == RPM_SUSPENDED &&
!dev->power.ignore_children &&
atomic_read(&dev->power.child_count) > 0,
"Enabling runtime PM for inactive device (%s) with active children\n",
dev_name(dev));
if (--dev->power.disable_depth > 0)
goto out;
dev->power.last_status = RPM_INVALID;
dev->power.accounting_timestamp = ktime_get_mono_fast_ns();
if (dev->power.runtime_status == RPM_SUSPENDED &&
!dev->power.ignore_children &&
atomic_read(&dev->power.child_count) > 0)
dev_warn(dev, "Enabling runtime PM for inactive device with active children\n");
out:
spin_unlock_irqrestore(&dev->power.lock, flags);
}
EXPORT_SYMBOL_GPL(pm_runtime_enable);
@ -1640,6 +1644,7 @@ EXPORT_SYMBOL_GPL(__pm_runtime_use_autosuspend);
void pm_runtime_init(struct device *dev)
{
dev->power.runtime_status = RPM_SUSPENDED;
dev->power.last_status = RPM_INVALID;
dev->power.idle_notification = false;
dev->power.disable_depth = 1;

2
include/linux/pm.h
View File

@ -521,6 +521,7 @@ const struct dev_pm_ops __maybe_unused name = { \
*/
enum rpm_status {
RPM_INVALID = -1,
RPM_ACTIVE = 0,
RPM_RESUMING,
RPM_SUSPENDED,
@ -634,6 +635,7 @@ struct dev_pm_info {
unsigned int links_count;
enum rpm_request request;
enum rpm_status runtime_status;
enum rpm_status last_status;
int runtime_error;
int autosuspend_delay;
u64 last_busy;