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

["Mun, Gwan-gyeong" <gwan-gyeong.mun@intel.com>]

On Mon, 2020-10-12 at 11:15 -0700, Souza, Jose wrote:
> 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?
> 
- Result with DMC firmware (tgl_dmc_ver2_08.bin, the latest drm-tip
requires this version) showes PSR screen glitch issue.
- Result without DMC firmware does not show PSR screen glitch issue.
> 
> > 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@intel.com>
> > > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > Signed-off-by: José Roberto de Souza <jose.souza@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
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