[PATCH 1/2] drm/i915/dp_mst: Handle error during DSC BW overhead/slice calculation

[Imre Deak]

On Thu, Oct 10, 2024 at 06:54:24AM +0300, Kandpal, Suraj wrote:
> 
> 
> > -----Original Message-----
> > From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf Of Imre
> > Deak
> > Sent: Wednesday, October 9, 2024 4:32 PM
> > To: intel-gfx at lists.freedesktop.org
> > Subject: [PATCH 1/2] drm/i915/dp_mst: Handle error during DSC BW
> > overhead/slice calculation
> >
> > The MST branch device may not support the number of DSC slices a mode
> > requires, handle the error in this case.
> >
> > Signed-off-by: Imre Deak <imre.deak at intel.com>
> 
> I feel this is a better implementation of the fix I had sent

Yes, noticed the same issue a while ago, but didn't want to send a fix
until figuring out how to handle modes for which DSC was force-enabled.
Simply returning an error from here would've left those not working at
all with some docks.

Thanks for the patch and review, pushed this patchset now to
drm-intel-next, Cc'ing stable and adding the Fixes: lines.

> LGTM,
> Reviewed-by: Suraj Kandpal <suraj.kandpal at intel.com>
> 
> > ---
> >  drivers/gpu/drm/i915/display/intel_dp_mst.c | 39 ++++++++++++++-------
> >  1 file changed, 27 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > index 4765bda154c15..2822ae1160034 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > @@ -90,27 +90,19 @@ static int intel_dp_mst_max_dpt_bpp(const struct
> > intel_crtc_state *crtc_state,
> >
> >  static int intel_dp_mst_bw_overhead(const struct intel_crtc_state
> > *crtc_state,
> >                                   const struct intel_connector *connector,
> > -                                 bool ssc, bool dsc, int bpp_x16)
> > +                                 bool ssc, int dsc_slice_count, int bpp_x16)
> >  {
> >       const struct drm_display_mode *adjusted_mode =
> >               &crtc_state->hw.adjusted_mode;
> >       unsigned long flags = DRM_DP_BW_OVERHEAD_MST;
> > -     int dsc_slice_count = 0;
> >       int overhead;
> >
> >       flags |= intel_dp_is_uhbr(crtc_state) ?
> > DRM_DP_BW_OVERHEAD_UHBR : 0;
> >       flags |= ssc ? DRM_DP_BW_OVERHEAD_SSC_REF_CLK : 0;
> >       flags |= crtc_state->fec_enable ? DRM_DP_BW_OVERHEAD_FEC : 0;
> >
> > -     if (dsc) {
> > -             int num_joined_pipes =
> > intel_crtc_num_joined_pipes(crtc_state);
> > -
> > +     if (dsc_slice_count)
> >               flags |= DRM_DP_BW_OVERHEAD_DSC;
> > -             dsc_slice_count = intel_dp_dsc_get_slice_count(connector,
> > -                                                            adjusted_mode-
> > >clock,
> > -                                                            adjusted_mode-
> > >hdisplay,
> > -
> > num_joined_pipes);
> > -     }
> >
> >       overhead = drm_dp_bw_overhead(crtc_state->lane_count,
> >                                     adjusted_mode->hdisplay,
> > @@ -156,6 +148,19 @@ static int intel_dp_mst_calc_pbn(int pixel_clock, int
> > bpp_x16, int bw_overhead)
> >       return DIV_ROUND_UP(effective_data_rate * 64, 54 * 1000);  }
> >
> > +static int intel_dp_mst_dsc_get_slice_count(const struct intel_connector
> > *connector,
> > +                                         const struct intel_crtc_state
> > *crtc_state) {
> > +     const struct drm_display_mode *adjusted_mode =
> > +             &crtc_state->hw.adjusted_mode;
> > +     int num_joined_pipes = intel_crtc_num_joined_pipes(crtc_state);
> > +
> > +     return intel_dp_dsc_get_slice_count(connector,
> > +                                         adjusted_mode->clock,
> > +                                         adjusted_mode->hdisplay,
> > +                                         num_joined_pipes);
> > +}
> > +
> >  static int intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder
> > *encoder,
> >                                               struct intel_crtc_state
> > *crtc_state,
> >                                               int max_bpp,
> > @@ -175,6 +180,7 @@ static int
> > intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder *encoder,
> >       const struct drm_display_mode *adjusted_mode =
> >               &crtc_state->hw.adjusted_mode;
> >       int bpp, slots = -EINVAL;
> > +     int dsc_slice_count = 0;
> >       int max_dpt_bpp;
> >       int ret = 0;
> >
> > @@ -206,6 +212,15 @@ static int
> > intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder *encoder,
> >       drm_dbg_kms(&i915->drm, "Looking for slots in range min bpp %d
> > max bpp %d\n",
> >                   min_bpp, max_bpp);
> >
> > +     if (dsc) {
> > +             dsc_slice_count =
> > intel_dp_mst_dsc_get_slice_count(connector, crtc_state);
> > +             if (!dsc_slice_count) {
> > +                     drm_dbg_kms(&i915->drm, "Can't get valid DSC slice
> > count\n");
> > +
> > +                     return -ENOSPC;
> > +             }
> > +     }
> > +
> >       for (bpp = max_bpp; bpp >= min_bpp; bpp -= step) {
> >               int local_bw_overhead;
> >               int remote_bw_overhead;
> > @@ -219,9 +234,9 @@ static int
> > intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder *encoder,
> >                                              intel_dp_output_bpp(crtc_state-
> > >output_format, bpp));
> >
> >               local_bw_overhead = intel_dp_mst_bw_overhead(crtc_state,
> > connector,
> > -                                                          false, dsc,
> > link_bpp_x16);
> > +                                                          false,
> > dsc_slice_count, link_bpp_x16);
> >               remote_bw_overhead =
> > intel_dp_mst_bw_overhead(crtc_state, connector,
> > -                                                           true, dsc,
> > link_bpp_x16);
> > +                                                           true,
> > dsc_slice_count, link_bpp_x16);
> >
> >               intel_dp_mst_compute_m_n(crtc_state, connector,
> >                                        local_bw_overhead,
> > --
> > 2.44.2
>