Re: [PATCH v2] iommu/arm-smmu: fix "hang" when games exit

[Robin Murphy]

On 2019-10-28 10:38 pm, Rob Clark wrote:
> On Mon, Oct 28, 2019 at 3:20 PM Will Deacon <will@xxxxxxxxxx> wrote:
> > Hi Rob,
> >
> > On Mon, Oct 07, 2019 at 01:49:06PM -0700, Rob Clark wrote:
> > > From: Rob Clark <robdclark@xxxxxxxxxxxx>
> > >
> > > When games, browser, or anything using a lot of GPU buffers exits, there
> > > can be many hundreds or thousands of buffers to unmap and free.  If the
> > > GPU is otherwise suspended, this can cause arm-smmu to resume/suspend
> > > for each buffer, resulting 5-10 seconds worth of reprogramming the
> > > context bank (arm_smmu_write_context_bank()/arm_smmu_write_s2cr()/etc).
> > > To the user it would appear that the system just locked up.
> > >
> > > A simple solution is to use pm_runtime_put_autosuspend() instead, so we
> > > don't immediately suspend the SMMU device.
> >
> > Please can you reword the subject to be a bit more useful? The commit
> > message is great, but the subject is a bit like "fix bug in code" to me.
>
> yeah, not the best $subject, but I wasn't quite sure how to fit
> something better in a reasonable # of chars.. maybe something like:
> "iommu/arm-smmu: optimize unmap but avoiding toggling runpm state"?

FWIW, I'd be inclined to frame it as something like "avoid pathological 
RPM behaviour for unmaps".

Robin.