[Intel-gfx] [PATCH] drm/i915/fbc: disable FBC on FIFO underruns

[Zanoni, Paulo R]

Em Seg, 2016-06-13 às 13:47 +0200, Stefan Richter escreveu:
> On Jun 10 Paulo Zanoni wrote:
> > 
> > Since my test machines don't produce FIFO underrun errors, I tested
> > this by
> > creating a debugfs file that just calls
> > intel_fbc_handle_fifo_underrun(). I'd
> > appreciate some Tested-by tags, if possible.
> Since May 8 I have been using 4.6.0-rc6 patched with
> drm-intel-nightly_2016y-05m-06d-14h-29m-58s (from what I understand,
> something close to what is now in mainline), and fbc disabled on the
> kernel commandline.  I have not rebooted since May 8.

Ok, so you're saying that if you boot this Kernel with i915.fbc=1, you
won't get any FIFO underrun messages, but the system is still going to
freeze somehow?

If that's the case, then this patch won't help.

> 
> For that kernel, i915.enable_fbc=0 is both required and sufficient to
> prevent freezes at random points in time (as reported).  The
> drm-intel-nightly_2016y-05m-06d-14h-29m-58s patch on the other hand
> has the
> effect that there are never any FIFO underruns logged anymore.
> 
> If there are no FIFO underruns reported in dmesg, your underrun
> detection routine would never hit, would it?

You're right, there's no need to test on this case.

> 
> If you nevertheless think it's worth trying, should I test it on top
> of
> 4.7-rc3 or on current drm-intel-nightly?