Re: [PATCH] drm/i915/icl: Update csc and gamma enable checks

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

On Thu, Oct 03, 2024 at 05:32:56PM +0300, Ville Syrjälä wrote:
> On Thu, Oct 03, 2024 at 07:22:37AM -0700, Matt Roper wrote:
> > On Thu, Oct 03, 2024 at 02:10:31PM +0300, Ville Syrjälä wrote:
> > > On Thu, Oct 03, 2024 at 02:33:41PM +0530, Sai Teja Pottumuttu wrote:
> > > > With ICL, we have a way to check if gamma and csc are enabled on
> > > > a pipe using bits in GAMMA_MODE and CSC_MODE. So, use them as well
> > > > along with the existing BOTTOM_COLOR checks.
> > > > 
> > > > BSpec: 7463, 7466
> > > > Signed-off-by: Sai Teja Pottumuttu <sai.teja.pottumuttu@intel.com>
> > > > ---
> > > >  drivers/gpu/drm/i915/display/intel_color.c | 24 ++++++++++++++++++++--
> > > >  1 file changed, 22 insertions(+), 2 deletions(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/i915/display/intel_color.c b/drivers/gpu/drm/i915/display/intel_color.c
> > > > index 50f41aeb3c28..1bf36898dc7e 100644
> > > > --- a/drivers/gpu/drm/i915/display/intel_color.c
> > > > +++ b/drivers/gpu/drm/i915/display/intel_color.c
> > > > @@ -1076,6 +1076,26 @@ static void skl_get_config(struct intel_crtc_state *crtc_state)
> > > >  		crtc_state->csc_enable = true;
> > > >  }
> > > >  
> > > > +static void icl_get_config(struct intel_crtc_state *crtc_state)
> > > > +{
> > > > +	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
> > > > +	struct drm_i915_private *i915 = to_i915(crtc->base.dev);
> > > > +	u32 bottom_color;
> > > > +
> > > > +	crtc_state->gamma_mode = hsw_read_gamma_mode(crtc);
> > > > +	crtc_state->csc_mode = ilk_read_csc_mode(crtc);
> > > > +
> > > > +	bottom_color = intel_de_read(i915, SKL_BOTTOM_COLOR(crtc->pipe));
> > > > +
> > > > +	if ((bottom_color & SKL_BOTTOM_COLOR_GAMMA_ENABLE) ||
> > > > +	    (crtc_state->gamma_mode & POST_CSC_GAMMA_ENABLE))
> > > > +		crtc_state->gamma_enable = true;
> > > > +
> > > > +	if ((bottom_color & SKL_BOTTOM_COLOR_CSC_ENABLE) ||
> > > > +	    (crtc_state->csc_mode & ICL_CSC_ENABLE))
> > > > +		crtc_state->csc_enable = true;
> > > 
> > > We don't use the old per-plane/bottom color way of enabling these.
> > > So this is not right.
> > 
> > I think that's the reason for the patch --- today we use
> > skl_get_config() which *only* checks the bottom color settings.  And
> > that approach is documented as being deprecated (although still
> > supported on current platforms).
> > 
> > If we're reading out pre-OS state programmed by the vbios, we probably
> > need to handle whichever approach it took, right?  Or are we sanitizing
> > this away to "off" somewhere that makes it okay to miss what was
> > programmed?
> 
> I think we're not doing anything. I suppose some kind of
> assert_legacy_color_stuff_is_off() thing somewhere could be a
> decent addition.

Or maybe we don't need to do anything. The state checker will catch
this problem with the current code as far as the pipe bottom color
is concerned. It won't catch inconsistent plane programming though.
But we also don't have such a consistency check for older platforms
either.

-- 
Ville Syrjälä
Intel