On Wed, 12 Jun 2013 00:48:25 +0100 Chris Wilson <chris at chris-wilson.co.uk> wrote: > On Tue, Jun 11, 2013 at 04:01:21PM -0700, St?phane Marchesin wrote: > > > > On Tue, Jun 11, 2013 at 3:57 PM, Chris Wilson <chris at chris-wilson.co.uk> wrote: > > > On Tue, Jun 11, 2013 at 03:49:27PM -0700, St?phane Marchesin wrote: > > >> During suspend all fences are reset, including their pin_count which > > >> is reset to 0. However a framebuffer can be bound across > > >> suspend/resume, which means that when the buffer is unbound after > > >> resume, the pin count for the buffer will be negative. Since the > > >> fence pin count is now negative when available and zero when in use, > > >> the buffer's fence will get recycled when the fence is in use which > > >> is the opposite of what we want. The visible effect is that since the > > >> fence is recycled the tiling mode goes away while the buffer is being > > >> displayed and we get lines/screens of garbage. > > >> > > >> To fix this, we repin the fences for all bound fbs on resume, which > > >> ensures the pin count is right. > > > > > > Yikes. So why do we not just keep the fences alive during suspend (not > > > touching their pin_count), and then just iterate over the list of fences > > > rewriting the register as required upon resume? That would seem less > > > error prone than trying to reconstruct the lost pin_count. > > > > I suspect they'd need to be saved/restored at the hw level as well, > > which AFAICS isn't happening today... > > Ugh, I introduced this bug 30 months ago - saved by the VT switch on > resume. But we can restore the fences from dev_priv->fence_regs... > Actually we have a very similar problem after a GPU reset where we > should restore fences for pinned objects (i.e. the scanout). The patch > to fix both looks fairly straightforward. To be clear, this only affects gen3 right? For gen4+ we don't need the fences for scanout since we have a bit in the plane control... Or are we failing to fault on a previously mapped scanout too? If so, we'd need to cover more than just scanout here. -- Jesse Barnes, Intel Open Source Technology Center
