[Intel-gfx] [PATCH 10/10] drm/i915: Stop loading linear degammma LUT on glk needlessly

[Shankar, Uma]

> -----Original Message-----
> From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf Of Ville Syrjala
> Sent: Thursday, September 29, 2022 12:45 PM
> To: intel-gfx at lists.freedesktop.org
> Subject: [Intel-gfx] [PATCH 10/10] drm/i915: Stop loading linear degammma LUT on
> glk needlessly

Typo in degamma

> 
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> Make glk_load_luts() a bit lighter for the common case where neither the degamma
> LUT nor pipe CSC are enabled by not loading the linear degamma LUT. Making
> .load_luts() as lightweight as possible is a good idea since it may need to execute
> from a vblank worker under tight deadlines.
> 
> My earlier reasoning for always loading the linear degamma LUT was to avoid an
> extra LUT load when just enabling/disabling the pipe CSC, but that is nonsense since
> we load the LUTs on every flagged color manaement change/modeset anyway

Nit pick: Typo in management.

With above fixed,
Reviewed-by: Uma Shankar <uma.shankar at intel.com>

> (either of which is needed for a pipe CSC toggle).
> 
> We can also get rid of the glk_can_preload_luts() special case since the presence of
> the degamma LUT will now always match csc_enable.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_color.c | 26 +++-------------------
>  1 file changed, 3 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_color.c
> b/drivers/gpu/drm/i915/display/intel_color.c
> index de530bf1aba1..a3066d942f58 100644
> --- a/drivers/gpu/drm/i915/display/intel_color.c
> +++ b/drivers/gpu/drm/i915/display/intel_color.c
> @@ -1198,24 +1198,6 @@ static bool chv_can_preload_luts(const struct
> intel_crtc_state *new_crtc_state)
>  	return !old_crtc_state->post_csc_lut;
>  }
> 
> -static bool glk_can_preload_luts(const struct intel_crtc_state *new_crtc_state) -{
> -	struct intel_crtc *crtc = to_intel_crtc(new_crtc_state->uapi.crtc);
> -	struct intel_atomic_state *state =
> -		to_intel_atomic_state(new_crtc_state->uapi.state);
> -	const struct intel_crtc_state *old_crtc_state =
> -		intel_atomic_get_old_crtc_state(state, crtc);
> -
> -	/*
> -	 * The hardware degamma is active whenever the pipe
> -	 * CSC is active. Thus even if the old state has no
> -	 * software degamma we need to avoid clobbering the
> -	 * linear hardware degamma mid scanout.
> -	 */
> -	return !old_crtc_state->csc_enable &&
> -		!old_crtc_state->post_csc_lut;
> -}
> -
>  int intel_color_check(struct intel_crtc_state *crtc_state)  {
>  	struct drm_i915_private *dev_priv = to_i915(crtc_state->uapi.crtc->dev);
> @@ -1622,11 +1604,9 @@ static void glk_assign_luts(struct intel_crtc_state
> *crtc_state)
>  	 * On GLK+ both pipe CSC and degamma LUT are controlled
>  	 * by csc_enable. Hence for the cases where the CSC is
>  	 * needed but degamma LUT is not we need to load a
> -	 * linear degamma LUT. In fact we'll just always load
> -	 * the degama LUT so that we don't have to reload
> -	 * it every time the pipe CSC is being enabled.
> +	 * linear degamma LUT.
>  	 */
> -	if (!crtc_state->pre_csc_lut)
> +	if (crtc_state->csc_enable && !crtc_state->pre_csc_lut)
>  		drm_property_replace_blob(&crtc_state->pre_csc_lut,
>  					  i915-
> >display.color.glk_linear_degamma_lut);
>  }
> @@ -1667,7 +1647,7 @@ static int glk_color_check(struct intel_crtc_state
> *crtc_state)
> 
>  	glk_assign_luts(crtc_state);
> 
> -	crtc_state->preload_luts = glk_can_preload_luts(crtc_state);
> +	crtc_state->preload_luts = intel_can_preload_luts(crtc_state);
> 
>  	return 0;
>  }
> --
> 2.35.1