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

[Manasi Navare <navaremanasi@chromium.org>]

Hi Imre,

Thanks for the DSC fixes.
Would the line buf depth calculation that was getting set to 0 impact
DSC on all platforms
or was this issue only specific to MTL and was getting set correctly
with older platforms?
We didnt notice any DSC issues/corruptions with ADL based systems.

The actual change makes sense, just want to confirm if this applies to
all platforms or any particular?
With that clarification:

Reviewed-by: Manasi Navare <navaremanasi@chromium.org>

Regards
Manasi

On Tue, Mar 26, 2024 at 3:01 AM Nautiyal, Ankit K
<ankit.k.nautiyal@intel.com> wrote:
>
>
> 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@lists.freedesktop.org
> > Signed-off-by: Imre Deak <imre.deak@intel.com>
>
> LGTM.
>
> Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@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