Messages in this thread | | | From | Ulf Hansson <> | Subject | [PATCH v2 0/3] PM: runtime: Update behaviour for no callbacks | Date | Tue, 8 Jun 2021 11:02:47 +0200 |
| |
While reviewing a patch on the mmc-list, I ended up inspecting the behaviour of how we deal with the no callback case for runtime PM.
A couple of observations:
*) When pm_runtime_no_callbacks() have been called, it allows the PM core to takes a quicker path, but at the same time, consumer/supplier device links are being skipped in rpm_resume|suspend().
**) Calling pm_runtime_no_callbacks() to avoid boiler plate code (assigning empty functions to ->runtime_suspend|resume()), doesn't work if there could be consumer/supplier device link being used or a platform dependent PM domain that could get attached to the device.
Therefore, this series suggests to change the behaviour in the PM core, to allow the ->runtime_suspend|resume() callbacks to be unassigned. This is already supported for ->runtime_idle() callbacks, so it would also move things into a more consistent behaviour.
I have looked at various error paths, in the kernel of callers of pm_runtime_get_sync(). I couldn't find anyone that made sense, that looked for the special error code, -ENOSYS, which is the error code getting returned when a callback is missing. Whether that is sufficient proof that these changes are 100% safe, I can't guarantee, but I think it would be worth a try as the benefits of avoiding boilerplate code and the corresponding additional code paths are quite nice, if you ask me.
Kind regards Ulf Hansson
Ulf Hansson (3): PM: runtime: Improve path in rpm_idle() when no callback PM: runtime: Allow unassigned ->runtime_suspend|resume callbacks PM: runtime: Clarify documentation when callbacks are unassigned
Documentation/power/runtime_pm.rst | 8 ++++++++ drivers/base/power/runtime.c | 18 ++++++++---------- 2 files changed, 16 insertions(+), 10 deletions(-)
-- 2.25.1
| |