On Wed, Jun 10, 2020 at 03:52:39PM -0300, Ezequiel Garcia wrote: > Hi everyone, > > Thanks for the patch. > > On Wed, 10 Jun 2020 at 07:33, Tomasz Figa <tfiga@xxxxxxxxxxxx> wrote: > > > > On Wed, Jun 10, 2020 at 12:29 PM Hans Verkuil <hverkuil@xxxxxxxxx> wrote: > > > > > > On 21/05/2020 19:11, Tomasz Figa wrote: > > > > Hi Jerry, > > > > > > > > On Wed, Dec 04, 2019 at 08:47:29PM +0800, Jerry-ch Chen wrote: > > > >> From: Pi-Hsun Shih <pihsun@xxxxxxxxxxxx> > > > >> > > > >> Add two functions that can be used to stop new jobs from being queued / > > > >> continue running queued job. This can be used while a driver using m2m > > > >> helper is going to suspend / wake up from resume, and can ensure that > > > >> there's no job running in suspend process. [snip] > > > > > > I assume this will be part of a future patch series that calls these new functions? > > > > The mtk-jpeg encoder series depends on this patch as well, so I guess > > it would go together with whichever is ready first. > > > > I would also envision someone changing the other existing drivers to > > use the helpers, as I'm pretty much sure some of them don't handle > > suspend/resume correctly. > > > > This indeed looks very good. If I understood the issue properly, > the change would be useful for both stateless (e.g. hantro, et al) > and stateful (e.g. coda) codecs. > > Hantro uses pm_runtime_force_suspend, and I believe that > could is enough for proper suspend/resume operation. Unfortunately, no. :( If the decoder is already decoding a frame, that would forcefully power off the hardware and possibly even cause a system lockup if we are unlucky to gate a clock in the middle of a bus transaction. I just inspected the code now and actually found one more bug in its power management handling. device_run() calls clk_bulk_enable() before pm_runtime_get_sync(), but only the latter is guaranteed to actually power on the relevant power domains, so we end up clocking unpowered hardware. > > I'm not seeing any code in CODA to handle this, so not sure > how it's handling suspend/resume. > > Maybe we can have CODA as the first user, given it's a well-maintained > driver and should be fairly easy to test. I remember checking a number of drivers using the m2m helpers randomly and none of them implemented suspend/resume correctly. I suppose that was not discovered because normally the userspace itself would stop the operation before the system is suspended, although it's not an API guarantee. Best regards, Tomasz
