Re: [Intel-gfx] [PATCH 1/4] drm/i915: Move PIPE_CHICKEN RMW out from the vblank evade critical section

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Feb 18, 2022 at 02:38:37PM +0200, Juha-Pekka Heikkila wrote:
> This patch set look all ok. That failed cursor test in ci run seem to be 
> flip flopping on other runs too on same icl box.

Yeah, some of those tests seem a bit flaky on the icls. 
Not sure what's causing that.

> 
> Reviewed-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>

Thanks.

> 
> On 2.2.2022 13.16, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > We don't want any RMWs in the part of the commit that happens
> > under vblank evasion. Eventually we want to use the DSB to
> > handle that and it can't read registers at all. Also reads
> > are just slowing us down needlessly.
> > 
> > Let's move the whole PIPE_CHICKEN stuff out from the critical
> > section since we don't have anything there that needs to be
> > syncrhonized with other plane/pipe registers. If we ever need
> > to add such things then we have to move it back, but without
> > doing any reads.
> > 
> > TODO: should look into eliminating the RMW anyway...
> > 
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >   drivers/gpu/drm/i915/display/intel_display.c | 7 ++++---
> >   1 file changed, 4 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> > index c431076f98a1..05713b64d4bc 100644
> > --- a/drivers/gpu/drm/i915/display/intel_display.c
> > +++ b/drivers/gpu/drm/i915/display/intel_display.c
> > @@ -8121,9 +8121,6 @@ static void intel_pipe_fastset(const struct intel_crtc_state *old_crtc_state,
> >   	if (DISPLAY_VER(dev_priv) >= 9 ||
> >   	    IS_BROADWELL(dev_priv) || IS_HASWELL(dev_priv))
> >   		hsw_set_linetime_wm(new_crtc_state);
> > -
> > -	if (DISPLAY_VER(dev_priv) >= 11)
> > -		icl_set_pipe_chicken(new_crtc_state);
> >   }
> >   
> >   static void commit_pipe_pre_planes(struct intel_atomic_state *state,
> > @@ -8215,6 +8212,10 @@ static void intel_update_crtc(struct intel_atomic_state *state,
> >   
> >   		if (new_crtc_state->update_pipe)
> >   			intel_encoders_update_pipe(state, crtc);
> > +
> > +		if (DISPLAY_VER(dev_priv) >= 11 &&
> > +		    new_crtc_state->update_pipe)
> > +			icl_set_pipe_chicken(new_crtc_state);
> >   	}
> >   
> >   	intel_fbc_update(state, crtc);

-- 
Ville Syrjälä
Intel