[PATCH 01/11] drm/i915/dp: Fix DSC line buffer depth programming

[Nautiyal, Ankit K]

On 3/21/2024 1:41 AM, Imre Deak wrote:
> Fix the calculation of the DSC line buffer depth. This is limited both
> by the source's and sink's maximum line buffer depth, but the former one
> was not taken into account. On all Intel platform's the source's maximum
> buffer depth is 13, so the overall limit is simply the minimum of the
> source/sink's limit, regardless of the DSC version.
>
> This leaves the DSI DSC line buffer depth calculation as-is, trusting
> VBT.
>
> On DSC version 1.2 for sinks reporting a maximum line buffer depth of 16
> the line buffer depth was incorrectly programmed as 0, leading to a
> corruption in color gradients / lines on the decompressed screen image.
>
> Cc: dri-devel at lists.freedesktop.org
> Signed-off-by: Imre Deak <imre.deak at intel.com>

LGTM.

Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>

> ---
>   drivers/gpu/drm/i915/display/intel_dp.c | 16 ++++++----------
>   include/drm/display/drm_dsc.h           |  3 ---
>   2 files changed, 6 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index af7ca00e9bc0a..dbe65651bf277 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -89,6 +89,9 @@
>   #define DP_DSC_MAX_ENC_THROUGHPUT_0		340000
>   #define DP_DSC_MAX_ENC_THROUGHPUT_1		400000
>   
> +/* Max DSC line buffer depth supported by HW. */
> +#define INTEL_DP_DSC_MAX_LINE_BUF_DEPTH		13
> +
>   /* DP DSC FEC Overhead factor in ppm = 1/(0.972261) = 1.028530 */
>   #define DP_DSC_FEC_OVERHEAD_FACTOR		1028530
>   
> @@ -1703,7 +1706,6 @@ static int intel_dp_dsc_compute_params(const struct intel_connector *connector,
>   {
>   	struct drm_i915_private *i915 = to_i915(connector->base.dev);
>   	struct drm_dsc_config *vdsc_cfg = &crtc_state->dsc.config;
> -	u8 line_buf_depth;
>   	int ret;
>   
>   	/*
> @@ -1732,20 +1734,14 @@ static int intel_dp_dsc_compute_params(const struct intel_connector *connector,
>   			connector->dp.dsc_dpcd[DP_DSC_DEC_COLOR_FORMAT_CAP - DP_DSC_SUPPORT] &
>   			DP_DSC_RGB;
>   
> -	line_buf_depth = drm_dp_dsc_sink_line_buf_depth(connector->dp.dsc_dpcd);
> -	if (!line_buf_depth) {
> +	vdsc_cfg->line_buf_depth = min(INTEL_DP_DSC_MAX_LINE_BUF_DEPTH,
> +				       drm_dp_dsc_sink_line_buf_depth(connector->dp.dsc_dpcd));
> +	if (!vdsc_cfg->line_buf_depth) {
>   		drm_dbg_kms(&i915->drm,
>   			    "DSC Sink Line Buffer Depth invalid\n");
>   		return -EINVAL;
>   	}
>   
> -	if (vdsc_cfg->dsc_version_minor == 2)
> -		vdsc_cfg->line_buf_depth = (line_buf_depth == DSC_1_2_MAX_LINEBUF_DEPTH_BITS) ?
> -			DSC_1_2_MAX_LINEBUF_DEPTH_VAL : line_buf_depth;
> -	else
> -		vdsc_cfg->line_buf_depth = (line_buf_depth > DSC_1_1_MAX_LINEBUF_DEPTH_BITS) ?
> -			DSC_1_1_MAX_LINEBUF_DEPTH_BITS : line_buf_depth;
> -
>   	vdsc_cfg->block_pred_enable =
>   		connector->dp.dsc_dpcd[DP_DSC_BLK_PREDICTION_SUPPORT - DP_DSC_SUPPORT] &
>   		DP_DSC_BLK_PREDICTION_IS_SUPPORTED;
> diff --git a/include/drm/display/drm_dsc.h b/include/drm/display/drm_dsc.h
> index bc90273d06a62..bbbe7438473d3 100644
> --- a/include/drm/display/drm_dsc.h
> +++ b/include/drm/display/drm_dsc.h
> @@ -40,9 +40,6 @@
>   #define DSC_PPS_RC_RANGE_MINQP_SHIFT		11
>   #define DSC_PPS_RC_RANGE_MAXQP_SHIFT		6
>   #define DSC_PPS_NATIVE_420_SHIFT		1
> -#define DSC_1_2_MAX_LINEBUF_DEPTH_BITS		16
> -#define DSC_1_2_MAX_LINEBUF_DEPTH_VAL		0
> -#define DSC_1_1_MAX_LINEBUF_DEPTH_BITS		13
>   
>   /**
>    * struct drm_dsc_rc_range_parameters - DSC Rate Control range parameters