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path: root/Documentation/power/runtime_pm.rst
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2021-12-17PM: runtime: Capture device status before disabling runtime PMRafael J. Wysocki
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>
2021-06-11PM: runtime: Clarify documentation when callbacks are unassignedUlf Hansson
Recent changes to the PM core allows ->runtime_suspend|resume callbacks to be unassigned. In the earlier behaviour the PM core would return -ENOSYS, when trying to runtime resume a device, for example. Let's update the documentation to clarify this. Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org> Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2021-05-31PM: runtime: document common mistake with pm_runtime_get_sync()Krzysztof Kozlowski
pm_runtime_get_sync(), contradictory to intuition, does not drop the runtime PM usage counter on errors which lead to several wrong usages in drivers (missing the put). pm_runtime_resume_and_get() was added as a better implementation so document the preference of using it, hoping it will stop bad patterns. Suggested-by: Marek Szyprowski <m.szyprowski@samsung.com> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com> [ rjw: Documentation change edits ] Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2021-04-09PM: runtime: Add documentation for pm_runtime_resume_and_get()Alan Stern
Commit dd8088d5a896 ("PM: runtime: Add pm_runtime_resume_and_get to deal with usage counter") added a new runtime-PM API function without updating the documentation in runtime_pm.rst. Add the missing documentation. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Fixes: dd8088d5a896 ("PM: runtime: Add pm_runtime_resume_and_get to deal with usage counter") Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2021-01-27PM: runtime: Fix typos and grammarBjorn Helgaas
Fix minor typos and grammatical issues. Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2020-03-04PM: runtime: Add pm_runtime_get_if_active()Sakari Ailus
pm_runtime_get_if_in_use() bumps up the PM-runtime usage count if it is not equal to zero and the device's PM-runtime status is 'active'. This works for drivers that do not use autoidle, but for those that do, the function returns zero even when the device is active. In order to maintain sane device state while the device is powered on in the hope that it'll be needed, pm_runtime_get_if_active(dev, true) returns a positive value if the device's PM-runtime status is 'active' when it is called, in which case it also increments the device's usage count. If the second argument of pm_runtime_get_if_active() is 'false', the function behaves just like pm_runtime_get_if_in_use(), so redefine the latter as a wrapper around the former. Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> [ rjw: Changelog ] Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2019-11-20PM: Wrap documentation to fit in 80 columnsBjorn Helgaas
Wrap to 80 columns. No textual change except to correct some "it's" that should be "its". Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2019-06-14docs: power: convert docs to ReST and rename to *.rstMauro Carvalho Chehab
Convert the PM documents to ReST, in order to allow them to build with Sphinx. The conversion is actually: - add blank lines and indentation in order to identify paragraphs; - fix tables markups; - add some lists markups; - mark literal blocks; - adjust title markups. At its new index.rst, let's add a :orphan: while this is not linked to the main index.rst file, in order to avoid build warnings. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Acked-by: Mark Brown <broonie@kernel.org> Acked-by: Srivatsa S. Bhat (VMware) <srivatsa@csail.mit.edu>