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. -Chris -- Chris Wilson, Intel Open Source Technology Centre
