[Intel-gfx] [PATCH] drm/i915/tgl/psr: Fix glitches when doing frontbuffer modifications

[Souza, Jose]

On Mon, 2020-10-12 at 19:12 +0100, Mun, Gwan-gyeong wrote:
> After applying this patch, the psr screen glitch issue is still seen.

Same IOMMU errors too? In my end it is fixed.
Can you also give a try without the DMC firmware and without this changes?


> On Fri, 2020-10-02 at 16:16 -0700, José Roberto de Souza wrote:
> > Writes to CURSURFLIVE in TGL are causing IOMMU errors and visual
> > glitches that are often reproduced when executing CPU intensive
> > workloads while a eDP 4K panel is attached.
> > 
> > Manually exiting PSR causes the frontbuffer to be updated without
> > glitches and the IOMMU errors are also gone but this comes at the
> > cost
> > of less time with PSR active.
> > 
> > So using this workaround until this issue is root caused and a better
> > fix is found.
> > 
> > The current code is already ready to enable PSR after this exit if
> > there is not other frontbuffer modifications.
> > 
> > Adding a new if block in psr_force_hw_tracking_exit() instead of
> > reuse
> > the else/gen8- block because the plan is to revert this workaround
> > as soon as a better solution is found.
> > 
> > Cc: Gwan-gyeong Mun <gwan-gyeong.mun at intel.com>
> > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_psr.c | 16 +++++++++++++++-
> >  1 file changed, 15 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_psr.c
> > b/drivers/gpu/drm/i915/display/intel_psr.c
> > index 8a9d0bdde1bf..8630121dbbbe 100644
> > --- a/drivers/gpu/drm/i915/display/intel_psr.c
> > +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> > @@ -1152,7 +1152,21 @@ void intel_psr_disable(struct intel_dp
> > *intel_dp,
> >  
> > 
> > 
> > 
> >  static void psr_force_hw_tracking_exit(struct drm_i915_private
> > *dev_priv)
> >  {
> > -	if (INTEL_GEN(dev_priv) >= 9)
> > +	if (IS_TIGERLAKE(dev_priv))
> > +		/*
> > +		 * Writes to CURSURFLIVE in TGL are causing IOMMU
> > errors and
> > +		 * visual glitches that are often reproduced when
> > executing
> > +		 * CPU intensive workloads while a eDP 4K panel is
> > attached.
> > +		 *
> > +		 * Manually exiting PSR causes the frontbuffer to be
> > updated
> > +		 * without glitches and the IOMMU errors are also gone
> > but
> > +		 * this comes at the cost of less time with PSR active.
> > +		 *
> > +		 * So using this workaround until this issue is root
> > caused
> > +		 * and a better fix is found.
> > +		 */
> > +		intel_psr_exit(dev_priv);
> > +	else if (INTEL_GEN(dev_priv) >= 9)
> >  		/*
> >  		 * Display WA #0884: skl+
> >  		 * This documented WA for bxt can be safely applied