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

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

On Thu, Oct 03, 2024 at 09:08:53PM +0530, Pottumuttu, Sai Teja wrote:
> 
> On 03-10-2024 20:28, Ville Syrjälä wrote:
> > 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.
> 
> So, are we essentially saying that we can completely remove BOTTOM_COLOR 
> from here and just move to using GAMMA_MODE, CSC_MODE for setting 
> gamma_enable and csc_enable?

No. The current code already works correctly, and pipe_csc_enable and 
gamma_enable are not meant to be used on icl+.

-- 
Ville Syrjälä
Intel