Re: [PATCH 01/10] drm/i915/dsc: change DSC param tables to follow the DSC model

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 28 Feb 2023, Dmitry Baryshkov <dmitry.baryshkov@linaro.org> wrote:
> After cross-checking DSC models (20150914, 20161212, 20210623) change
> values in rc_parameters tables to follow config files present inside
> the DSC model. Handle two places, where i915 tables diverged from the
> model, by patching the rc values in the code.
>
> Note: I left one case uncorrected, 8bpp/10bpc/range_max_qp[0], because
> the table in the VESA DSC 1.1 sets it to 4.
>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> ---
>  drivers/gpu/drm/i915/display/intel_vdsc.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_vdsc.c b/drivers/gpu/drm/i915/display/intel_vdsc.c
> index 207b2a648d32..d080741fd0b3 100644
> --- a/drivers/gpu/drm/i915/display/intel_vdsc.c
> +++ b/drivers/gpu/drm/i915/display/intel_vdsc.c
> @@ -86,7 +86,7 @@ static const struct rc_parameters rc_parameters[][MAX_COLUMN_INDEX] = {
>  		}
>  	},
>  	/* 6BPP/14BPC */
> -	{ 768, 15, 6144, 15, 25, 23, 27, {
> +	{ 768, 15, 6144, 15, 25, 23, 23, {
>  		{ 0, 16, 0 }, { 7, 18, -2 }, { 15, 20, -2 }, { 16, 20, -4 },
>  		{ 17, 21, -6 }, { 17, 21, -6 }, { 18, 21, -6 }, { 18, 22, -8 },
>  		{ 19, 23, -8 }, { 20, 24, -10 }, { 21, 24, -10 },
> @@ -115,6 +115,10 @@ static const struct rc_parameters rc_parameters[][MAX_COLUMN_INDEX] = {
>  	},
>  	/* 8BPP/10BPC */
>  	{ 512, 12, 6144, 7, 16, 15, 15, {
> +		/*
> +		 * DSC model/pre-SCR-cfg has 8 for range_max_qp[0], however
> +		 * VESA DSC 1.1 Table E-5 sets it to 4.
> +		 */
>  		{ 0, 4, 2 }, { 4, 8, 0 }, { 5, 9, 0 }, { 5, 10, -2 },
>  		{ 7, 11, -4 }, { 7, 11, -6 }, { 7, 11, -8 }, { 7, 12, -8 },
>  		{ 7, 13, -8 }, { 7, 14, -10 }, { 9, 15, -10 }, { 9, 16, -12 },
> @@ -132,7 +136,7 @@ static const struct rc_parameters rc_parameters[][MAX_COLUMN_INDEX] = {
>  	},
>  	/* 8BPP/14BPC */
>  	{ 512, 12, 6144, 15, 24, 23, 23, {
> -		{ 0, 12, 0 }, { 5, 13, 0 }, { 11, 15, 0 }, { 12, 17, -2 },
> +		{ 0, 12, 2 }, { 5, 13, 0 }, { 11, 15, 0 }, { 12, 17, -2 },
>  		{ 15, 19, -4 }, { 15, 19, -6 }, { 15, 19, -8 }, { 15, 20, -8 },
>  		{ 15, 21, -8 }, { 15, 22, -10 }, { 17, 22, -10 },
>  		{ 17, 23, -12 }, { 17, 23, -12 }, { 21, 24, -12 },
> @@ -529,6 +533,16 @@ int intel_dsc_compute_params(struct intel_crtc_state *pipe_config)
>  			DSC_RANGE_BPG_OFFSET_MASK;
>  	}
>  
> +	if (DISPLAY_VER(dev_priv) < 13) {
> +		if (compressed_bpp == 6 &&
> +		    vdsc_cfg->bits_per_component == 8)
> +			vdsc_cfg->rc_quant_incr_limit1 = 23;
> +
> +		if (compressed_bpp == 8 &&
> +		    vdsc_cfg->bits_per_component == 14)
> +			vdsc_cfg->rc_range_params[0].range_bpg_offset = 0;
> +	}
> +

I wonder if we shouldn't just use the updated values...

Maybe add a FIXME comment above the block to consider removing it?

Reviewed-by: Jani Nikula <jani.nikula@intel.com>


>  	/*
>  	 * BitsPerComponent value determines mux_word_size:
>  	 * When BitsPerComponent is less than or 10bpc, muxWordSize will be equal to

-- 
Jani Nikula, Intel Open Source Graphics Center