On 2013-11-05 23:29, Ulf Hansson wrote: > On 23 October 2013 12:11, Tomi Valkeinen wrote: >> Hi, >> >> I was debugging why clocks were left enabled after removing omapdss >> driver, and I found this commit: >> >> fa180eb448fa263cf18dd930143b515d27d70d7b (PM / Runtime: Idle devices >> asynchronously after probe|release) >> >> I don't understand how that is supposed to work. >> >> When a driver is removed, instead of using pm_runtime_put_sync() the >> commit uses pm_runtime_put(), so the runtime_suspend call is queued. But >> who is going to handle the queued suspend call, as the driver is already >> removed? At least in my case, obviously nobody, as I only get >> runtime_resume call in my driver, never the runtime_suspend. >> >> Is there something I need to add to my driver to make this work, or >> should that part of the patch be reverted? > > I believe it is quite common that a device driver calls > pm_runtime_get_sync as a part of it's remove callback, then it > explicitly returns it's resources that has been fetched during probe. > Like a clk_disable_unprepare for example. I guess you mean the driver calls pm_runtime_get_sync _and_ pm_runtime_put_sync as part of its remove callback? Probably bus drivers need to do that, but for memory mapped devices in a SoC, I don't think there's normally any need to do pm_runtime_get/put_sync during the remove callback. > The idea behind the change in __device_release_driver, was to try to > prevent devices from going active->idle->active and instead just > remain active (if possible). > > In your case, which seems like a more modern way of implementing > "remove", you shall call "pm_runtime_suspend" to make sure the > runtime_suspend callbacks gets called. And as far as I understand, the change creates an explicit requirement to do either pm_runtime_get/put_sync or pm_runtime_suspend inside driver's remove callback. If so, that should be mentioned in big red letters in the pm-runtime documentation. The runtime_pm.txt doc does mention something related to this (and btw, the doc says pm_runtime_put_sync is being called, which is no longer true), but nothing clear about how the driver remove callback must be implemented. I tried grepping the kernel sources to find out if pm_runtime_suspend is widely used to get SoC platform devices to suspend, but it doesn't seem like it is. I didn't see pm_runtime_get/put_sync being used in remove callbacks widely either, but that was more difficult one to grep. Tomi