[Intel-gfx] [PATCH] drm/i915: Wait for vblank after register read

[Mika Kahola]

On Thu, 2018-04-19 at 09:11 +0300, Lofstedt, Marta wrote:
> For the PW results: 
> https://patchwork.freedesktop.org/series/41877/
> 
> it didn't fix the CRC mismatch on:
>  https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_8731/shard-
> snb6/igt at kms_frontbuffer_tracking@fbc-1p-pri-indfb-multidraw.html
This was expected that removing one vblank doesn't fix have an effect
on crc mismatches. Theres something more in this issue.

> 
> but that test has always failed on SNB: 
> http://gfx-ci.fi.intel.com/cibuglog/?action_failures_history=-1&failu
> res_test=igt at kms_frontbuffer_tracking@fbc-1p-pri-indfb-
> multidraw&failures_machine=shard-snb
> 
> so I don't think you brake anything with this patch.
> 
> Mika, do you know if waiting for the extra vblank was done with some
> purpose?
That I don't know if it was intentional. I'll try to find out why it
was needed.

> 
> 
> > 
> > -----Original Message-----
> > From: Intel-gfx [mailto:intel-gfx-bounces at lists.freedesktop.org] On
> > Behalf
> > Of Mika Kahola
> > Sent: Wednesday, April 18, 2018 10:57 AM
> > To: intel-gfx at lists.freedesktop.org
> > Subject: [Intel-gfx] [PATCH] drm/i915: Wait for vblank after
> > register read
> > 
> > When reading out CRC's we  wait for a vblank on
> > intel_dp_sink_crc_start()
> > function. When we start reading out CRC's in intel_dp_sink_crc()
> > loop we
> > first wait for a vblank yielding that all in all we end up waiting
> > two vblanks on
> > the first iteration round. Therefore, let's move the
> > intel_wait_for_vblank() as the last routine that we do in an
> > iteration loop in
> > intel_dp_sink_crc().
> > 
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103166
> > Signed-off-by: Mika Kahola <mika.kahola at intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_dp.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c
> > b/drivers/gpu/drm/i915/intel_dp.c index 62f82c4..6eb97fa 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -3972,13 +3972,14 @@ int intel_dp_sink_crc(struct intel_dp
> > *intel_dp,
> > struct intel_crtc_state *crtc_s
> >  		return ret;
> > 
> >  	do {
> > -		intel_wait_for_vblank(dev_priv, intel_crtc-
> > > 
> > > pipe);
> > -
> >  		if (drm_dp_dpcd_readb(&intel_dp->aux,
> > 
> > DP_TEST_SINK_MISC, &buf) < 0) {
> >  			ret = -EIO;
> >  			goto stop;
> >  		}
> > +
> > +		intel_wait_for_vblank(dev_priv, intel_crtc-
> > > 
> > > pipe);
> > +
> >  		count = buf & DP_TEST_COUNT_MASK;
> > 
> >  	} while (--attempts && count == 0);
> > --
> > 2.7.4
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
-- 
Mika Kahola - Intel OTC