Re: [Intel-gfx] [PATCH 18/18] drm/i915/display13: Enabling dithering after the CC1 pipe

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

On Thu, Jan 28, 2021 at 11:24:13AM -0800, Matt Roper wrote:
> From: Nischal Varide <nischal.varide@intel.com>
> 
> If the panel is 12bpc then Dithering is not enabled in the Legacy
> dithering block , instead its Enabled after the C1 CC1 pipe post
> color space conversion.For a 6bpc pannel Dithering is enabled in
> Legacy block.

Dithering is probably going to require a whole uapi bikeshed.
Not sure we can just enable it unilaterally.

Ccing dri-devel, and Mario who had issues with dithering in the
past...

> 
> Cc: Uma Shankar <uma.shankar@intel.com>
> Signed-off-by: Nischal Varide <nischal.varide@intel.com>
> Signed-off-by: Bhanuprakash Modem <bhanuprakash.modem@intel.com>
> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_color.c   | 16 ++++++++++++++++
>  drivers/gpu/drm/i915/display/intel_display.c |  9 ++++++++-
>  drivers/gpu/drm/i915/i915_reg.h              |  3 ++-
>  3 files changed, 26 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_color.c b/drivers/gpu/drm/i915/display/intel_color.c
> index ff7dcb7088bf..9a0572bbc5db 100644
> --- a/drivers/gpu/drm/i915/display/intel_color.c
> +++ b/drivers/gpu/drm/i915/display/intel_color.c
> @@ -1604,6 +1604,20 @@ static u32 icl_csc_mode(const struct intel_crtc_state *crtc_state)
>  	return csc_mode;
>  }
>  
> +static u32 dither_after_cc1_12bpc(const struct intel_crtc_state *crtc_state)
> +{
> +	u32 gamma_mode = crtc_state->gamma_mode;
> +	struct drm_i915_private *i915 = to_i915(crtc_state->uapi.crtc->dev);
> +
> +	if (HAS_DISPLAY13(i915)) {
> +		if (!crtc_state->dither_force_disable &&
> +		    (crtc_state->pipe_bpp == 36))
> +			gamma_mode |= GAMMA_MODE_DITHER_AFTER_CC1;
> +	}
> +
> +	return gamma_mode;
> +}
> +
>  static int icl_color_check(struct intel_crtc_state *crtc_state)
>  {
>  	int ret;
> @@ -1614,6 +1628,8 @@ static int icl_color_check(struct intel_crtc_state *crtc_state)
>  
>  	crtc_state->gamma_mode = icl_gamma_mode(crtc_state);
>  
> +	crtc_state->gamma_mode = dither_after_cc1_12bpc(crtc_state);
> +
>  	crtc_state->csc_mode = icl_csc_mode(crtc_state);
>  
>  	crtc_state->preload_luts = intel_can_preload_luts(crtc_state);
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index 4dc4b1be0809..e3dbcd956fc6 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -8098,9 +8098,15 @@ static void bdw_set_pipemisc(const struct intel_crtc_state *crtc_state)
>  		break;
>  	}
>  
> -	if (crtc_state->dither)
> +	/*
> +	 * If 12bpc panel then, Enables dithering after the CC1 pipe
> +	 * post color space conversion and not here
> +	 */
> +
> +	if (crtc_state->dither && (crtc_state->pipe_bpp != 36))
>  		val |= PIPEMISC_DITHER_ENABLE | PIPEMISC_DITHER_TYPE_SP;
>  
> +
>  	if (crtc_state->output_format == INTEL_OUTPUT_FORMAT_YCBCR420 ||
>  	    crtc_state->output_format == INTEL_OUTPUT_FORMAT_YCBCR444)
>  		val |= PIPEMISC_OUTPUT_COLORSPACE_YUV;
> @@ -10760,6 +10766,7 @@ intel_modeset_pipe_config(struct intel_atomic_state *state,
>  	 */
>  	pipe_config->dither = (pipe_config->pipe_bpp == 6*3) &&
>  		!pipe_config->dither_force_disable;
> +
>  	drm_dbg_kms(&i915->drm,
>  		    "hw max bpp: %i, pipe bpp: %i, dithering: %i\n",
>  		    base_bpp, pipe_config->pipe_bpp, pipe_config->dither);
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 128b835c0adb..27f25214a839 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -6132,7 +6132,7 @@ enum {
>  #define   PIPEMISC_DITHER_8_BPC		(0 << 5)
>  #define   PIPEMISC_DITHER_10_BPC	(1 << 5)
>  #define   PIPEMISC_DITHER_6_BPC		(2 << 5)
> -#define   PIPEMISC_DITHER_12_BPC	(3 << 5)
> +#define   PIPEMISC_DITHER_12_BPC	(4 << 5)
>  #define   PIPEMISC_DITHER_ENABLE	(1 << 4)
>  #define   PIPEMISC_DITHER_TYPE_MASK	(3 << 2)
>  #define   PIPEMISC_DITHER_TYPE_SP	(0 << 2)
> @@ -7668,6 +7668,7 @@ enum {
>  #define  GAMMA_MODE_MODE_12BIT	(2 << 0)
>  #define  GAMMA_MODE_MODE_SPLIT	(3 << 0) /* ivb-bdw */
>  #define  GAMMA_MODE_MODE_12BIT_MULTI_SEGMENTED	(3 << 0) /* icl + */
> +#define  GAMMA_MODE_DITHER_AFTER_CC1 (1 << 26)
>  
>  /* DMC/CSR */
>  #define CSR_PROGRAM(i)		_MMIO(0x80000 + (i) * 4)
> -- 
> 2.25.4
> 
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-- 
Ville Syrjälä
Intel
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