Hi Sakari, On Thu, Apr 06, 2023 at 04:36:25PM +0300, Sakari Ailus wrote: > On Thu, Apr 06, 2023 at 04:33:38AM +0300, Laurent Pinchart wrote: > > On Wed, Apr 05, 2023 at 03:52:52PM +0300, Sakari Ailus wrote: > > > On Wed, Apr 05, 2023 at 11:29:03AM +0200, Martin Kepplinger wrote: > > > > pm_runtime_get_if_in_use() does not only return nonzero values when > > > > the device is in use, it can return a negative errno too. > > > > > > > > And especially during resuming from system suspend, when runtime pm > > > > is not yet up again, this can very well happen. And in such a case > > > > the subsequent pm_runtime_put() call would result in a refcount underflow! > > > > > > I think this issue should have a more generic solution, it's very difficult > > > to address this in drivers only with the current APIs. > > > > > > pm_runtime_get_if_in_use() will also return an error if runtime PM is > > > disabled, so this patch will break the driver for that configuration. > > > > I'm increasingly inclined to depend on CONFIG_PM for all camera sensor > > drivers. > > For what reason? This is the smallest of all problems related to power > management. Also runtime PM has no-op functions for just this purpose. Because it creates a myriad of sleep (or bigger) issues like this one, and more seem to be popping up (or coming to my attention at least) over time. > (Frankly it'd be great if we could make CONFIG_PM go away. So perhaps > requiring it everywhere is one feasible approach to do that.) I'm all for it :-) For camera sensor drivers, are you aware of use cases where !CONFIG_PM would be desired ? -- Regards, Laurent Pinchart
