On 21 April 2016 at 01:30, Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote: > Hello, > > Reviving this old thread. > > On Monday 07 Mar 2016 11:10:08 Ulf Hansson wrote: >> [...] >> >> >> I agree, that's a better idea. Drivers shouldn't call >> >> pm_runtime_force_resume() if they haven't called >> >> pm_runtime_force_suspend(), so checking the PM use count should be fine. >> >> I'll modify the patch, test it and resubmit. >> > >> > I gave it an unfortunately unsuccessful try. The problem I ran into is >> > that device_prepare() calls pm_runtime_get_noresume() calls >> > pm_runtime_get_noresume(), with the corresponding pm_runtime_put() call >> > being performed in device_complete(). The device power usage_count is >> > thus always non-zero in the system resume handler, so I can't base the >> > decision on that. >> >> As Alan said, let's just check against 1 instead. > > I gave this a try, and unfortunately it won't work. > > pm_genpd_prepare() resumes devices without increasing the usage count, which It doesn't resume them, it only increases the usage count. > leads to the device always being active in pm_runtime_force_suspend(). The > usage count will be 1 if the device was suspended prior to entering system > suspend (due to the pm_runtime_get_noresume() call in device_prepare()) or > higher than 1 if the device was active. It's only greater than 1 - if someone else than the PM core has increased the usage count. > > However, pm_genpd_prepare() will not resume the device if suspend_power_off is > set. In that case the device will be suspended with a usage count of 1 in > pm_runtime_force_suspend() or active with a usage count higher than 1. > > We thus can't detect at resume time whether we have force-suspended the device > using the usage count. We don't need to detect this no more! Let me give you some background to why. When the pm_runtime_force_suspend|resume() helpers were invented, we still had CONFIG_PM_RUNTIME and CONFIG_PM_SLEEP as separate Kconfig options. To make sure these helpers worked for all combinations and without introducing too much complexity, we needed to always resume the device in pm_runtime_force_resume(). More precisely, when CONFIG_PM_SLEEP was used without CONFIG_PM_RUNTIME, we needed to resume the device as the driver/subsystem couldn't do it via a call to pm_runtime_get_sync() (or similar API). As we have merged CONFIG_PM_RUNTIME into CONFIG_PM, the above described option has disappeared. This means the driver/bus indeed will be able to use pm_runtime_get_sync() to resume the device at a later point when needed. > > Unless someone has another clever idea I'll keep the power.is_force_suspended > flag and protect it with power.lock. > >> > I also noticed that pm_genpd_prepare() runtime-resumes the device (when >> > the power domain is in the GPD_STATE_ACTIVE state). I don't know why that >> > is, but it means that in practice my device gets runtime-resumed when >> > suspending the system while it could stay runtime-suspended in practice. >> >> I am aware of this and it's on my TODO list of improvements of genpd, >> The issue is related to an unoptimized behaviour for how genpd deal >> with wakeups during system PM. > > Looking forward to seeing patches :-) I have been cooking a patch. Very soon I will post it and will make sure you are on cc! Of course any help in testing/reviewing will be highly appreciated! Kind regards Uffe
