kernel/linux.git/Documentation/power/runtime_pm.rst, branch linux-7.1.y

PM: sleep: Do not flag runtime PM workqueue as freezable

2025-12-15T11:20:02+00:00

Till now, the runtime PM workqueue has been flagged as freezable, so it does not process work items during system-wide PM transitions like system suspend and resume. The original reason to do that was to reduce the likelihood of runtime PM getting in the way of system-wide PM processing, but now it is mostly an optimization because (1) runtime suspend of devices is prevented by bumping up their runtime PM usage counters in device_prepare() and (2) device drivers are expected to disable runtime PM for the devices handled by them before they embark on system-wide PM activities that may change the state of the hardware or otherwise interfere with runtime PM. However, it prevents asynchronous runtime resume of devices from working during system-wide PM transitions, which is confusing because synchronous runtime resume is not prevented at the same time, and it also sometimes turns out to be problematic. For example, it has been reported that blk_queue_enter() may deadlock during a system suspend transition because of the pm_request_resume() usage in it [1]. It may also deadlock during a system resume transition in a similar way. That happens because the asynchronous runtime resume of the given device is not processed due to the freezing of the runtime PM workqueue. While it may be better to address this particular issue in the block layer, the very presence of it means that similar problems may be expected to occur elsewhere. For this reason, remove the WQ_FREEZABLE flag from the runtime PM workqueue and make device_suspend_late() use the generic variant of pm_runtime_disable() that will carry out runtime PM of the device synchronously if there is pending resume work for it. Also update the comment before the pm_runtime_disable() call in device_suspend_late(), to document the fact that the runtime PM should not be expected to work for the device until the end of device_resume_early(), and update the related documentation. This change may, even though it is not expected to, uncover some latent issues related to queuing up asynchronous runtime resume work items during system suspend or hibernation. However, they should be limited to the interference between runtime resume and system-wide PM callbacks in the cases when device drivers start to handle system-wide PM before disabling runtime PM as described above. Link: https://lore.kernel.org/linux-pm/20251126101636.205505-2-yang.yang@vivo.com/ Signed-off-by: Rafael J. Wysocki Reviewed-by: Ulf Hansson Link: https://patch.msgid.link/12794222.O9o76ZdvQC@rafael.j.wysocki

PM: runtime: Make pm_runtime_barrier() return void

2025-12-04T19:38:13+00:00

No callers check the return code, and that's a good thing. Doing so would be racy and unhelpful. Drop the return code entirely, so we don't make anyone think about its complexities. Signed-off-by: Brian Norris Tested-by: Guenter Roeck Link: https://patch.msgid.link/20251202193129.1411419-2-briannorris@chromium.org Signed-off-by: Rafael J. Wysocki

PM: runtime: docs: Update pm_runtime_allow/forbid() documentation

2025-10-23T14:13:33+00:00

Drop confusing descriptions of pm_runtime_allow() and pm_runtime_forbid() from Documentation/power/runtime_pm.rst and update the kerneldoc comments of these functions to better explain their purpose. Link: https://lore.kernel.org/linux-pm/08976178-298f-79d9-1d63-cff5a4e56cc3@linux.intel.com/ Signed-off-by: Rafael J. Wysocki Reviewed-by: Brian Norris Reviewed-by: Ulf Hansson Reviewed-by: Ilpo Järvinen Link: https://patch.msgid.link/12780841.O9o76ZdvQC@rafael.j.wysocki

Documentation: PM: *_autosuspend() functions update last busy time

2025-06-18T19:41:08+00:00

Document that the *_autosuspend() variants of the Runtime PM functions update the last busy timestamp. Signed-off-by: Sakari Ailus Reviewed-by: Laurent Pinchart Link: https://patch.msgid.link/20250616061212.2286741-7-sakari.ailus@linux.intel.com Signed-off-by: Rafael J. Wysocki

PM: runtime: Mark last busy stamp in pm_request_autosuspend()

2025-06-18T19:41:08+00:00

Set device's last busy timestamp to current time in pm_request_autosuspend(). Signed-off-by: Sakari Ailus Reviewed-by: Laurent Pinchart Link: https://patch.msgid.link/20250616061212.2286741-6-sakari.ailus@linux.intel.com Signed-off-by: Rafael J. Wysocki

PM: runtime: Mark last busy stamp in pm_runtime_autosuspend()

2025-06-18T19:41:08+00:00

Set device's last busy timestamp to current time in pm_runtime_autosuspend(). Signed-off-by: Sakari Ailus Reviewed-by: Laurent Pinchart Link: https://patch.msgid.link/20250616061212.2286741-5-sakari.ailus@linux.intel.com Signed-off-by: Rafael J. Wysocki

PM: runtime: Mark last busy stamp in pm_runtime_put_sync_autosuspend()

2025-06-18T19:41:08+00:00

Set device's last busy timestamp to current time in pm_runtime_put_sync_autosuspend(). Signed-off-by: Sakari Ailus Reviewed-by: Laurent Pinchart Link: https://patch.msgid.link/20250616061212.2286741-4-sakari.ailus@linux.intel.com Signed-off-by: Rafael J. Wysocki

PM: runtime: Mark last busy stamp in pm_runtime_put_autosuspend()

2025-06-18T19:41:08+00:00

Set device's last busy timestamp to current time in pm_runtime_put_autosuspend(). Callers wishing not to do that will need to use __pm_runtime_put_autosuspend(). Signed-off-by: Sakari Ailus Reviewed-by: Laurent Pinchart Link: https://patch.msgid.link/20250616061212.2286741-3-sakari.ailus@linux.intel.com Signed-off-by: Rafael J. Wysocki

Documentation: PM: runtime: Fix a reference to pm_runtime_autosuspend()

2025-04-15T17:23:58+00:00

pm_runtime_autosuspend() got accidentally renamed as __pm_runtime_autosuspend() whereas the intention in the patch was to rename pm_runtime_put_autosuspend() only. Fix it. Fixes: b7d46644e554 ("PM: runtime: Add pm_runtime_put_autosuspend() replacement") Signed-off-by: Sakari Ailus Reviewed-by: Laurent Pinchart Link: https://patch.msgid.link/20250410153106.4146265-2-sakari.ailus@linux.intel.com Signed-off-by: Rafael J. Wysocki

Documentation: PM: Clarify pm_runtime_resume_and_get() return value

2024-12-10T19:14:22+00:00

Update the documentation to match the behaviour of the code. pm_runtime_resume_and_get() always returns 0 on success, even if __pm_runtime_resume() returns 1. Fixes: 2c412337cfe6 ("PM: runtime: Add documentation for pm_runtime_resume_and_get()") Signed-off-by: Paul Barker Link: https://patch.msgid.link/20241203143729.478-1-paul.barker.ct@bp.renesas.com [ rjw: Subject and changelog edits, adjusted new comment formatting ] Signed-off-by: Rafael J. Wysocki