>
> On Thu, 17 Aug 2023, Imre Deak <imre.deak@xxxxxxxxx> wrote:
> > A follow-up patch will need to limit the output link bpp both in the
> > non-DSC and DSC configuration, so track the pipe and link bpp limits
> > separately in the link_config_limits struct.
> >
> > Use .4 fixed point format for link bpp matching the 1/16 bpp
> > granularity in DSC mode and for now keep this limit matching the pipe bpp
> limit.
> >
> > Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/display/intel_dp.c | 17 +++++++++++------
> > drivers/gpu/drm/i915/display/intel_dp.h | 9 ++++++++-
> > drivers/gpu/drm/i915/display/intel_dp_mst.c | 17 +++++++++++------
> > 3 files changed, 30 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> > b/drivers/gpu/drm/i915/display/intel_dp.c
> > index 89de444cfc4da..f4952fcfb16e9 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -1419,7 +1419,7 @@ intel_dp_adjust_compliance_config(struct
> intel_dp *intel_dp,
> > if (intel_dp->compliance.test_data.bpc != 0) {
> > int bpp = 3 * intel_dp->compliance.test_data.bpc;
> >
> > - limits->min_bpp = limits->max_bpp = bpp;
> > + limits->pipe.min_bpp = limits->pipe.max_bpp = bpp;
> > pipe_config->dither_force_disable = bpp == 6 * 3;
> >
> > drm_dbg_kms(&i915->drm, "Setting pipe_bpp to %d\n",
> bpp); @@
> > -1481,7 +1481,9 @@ intel_dp_compute_link_config_wide(struct intel_dp
> *intel_dp,
> > int bpp, i, lane_count, clock = intel_dp_mode_clock(pipe_config,
> conn_state);
> > int mode_rate, link_rate, link_avail;
> >
> > - for (bpp = limits->max_bpp; bpp >= limits->min_bpp; bpp -= 2 * 3) {
> > + for (bpp = limits->link.max_bpp >> 4;
> > + bpp >= limits->link.min_bpp >> 4;
>
> I think I'd like to see some helpers for the >> 4 and << 4, to make this self-
> documenting code.
>
> to_bpp_int(), to_bpp_x16(), or something along those lines maybe.
>
> With proper variable/member naming, you'd get:
>
> bpp = to_bpp_int(bpp_x16);
> bpp_x16 = to_bpp_x16(bpp);
>
> And it would be obvious what's going on.
>
> > + bpp -= 2 * 3) {
> > int output_bpp = intel_dp_output_bpp(pipe_config-
> >output_format,
> > bpp);
> >
> > mode_rate = intel_dp_link_required(clock, output_bpp); @@
> -1812,9
> > +1814,9 @@ intel_dp_compute_config_limits(struct intel_dp *intel_dp,
> > limits->min_lane_count = 1;
> > limits->max_lane_count = intel_dp_max_lane_count(intel_dp);
> >
> > - limits->min_bpp = intel_dp_min_bpp(crtc_state->output_format);
> > - limits->max_bpp = intel_dp_max_bpp(intel_dp, crtc_state,
> > - respect_downstream_limits);
> > + limits->pipe.min_bpp = intel_dp_min_bpp(crtc_state-
> >output_format);
> > + limits->pipe.max_bpp = intel_dp_max_bpp(intel_dp, crtc_state,
> > +
> respect_downstream_limits);
> >
> > if (intel_dp->use_max_params) {
> > /*
> > @@ -1831,10 +1833,13 @@ intel_dp_compute_config_limits(struct
> intel_dp
> > *intel_dp,
> >
> > intel_dp_adjust_compliance_config(intel_dp, crtc_state, limits);
> >
> > + limits->link.min_bpp = limits->pipe.min_bpp << 4;
> > + limits->link.max_bpp = limits->pipe.max_bpp << 4;
> > +
> > drm_dbg_kms(&i915->drm, "DP link computation with max lane
> count %i "
> > "max rate %d max bpp %d pixel clock %iKHz\n",
> > limits->max_lane_count, limits->max_rate,
> > - limits->max_bpp, adjusted_mode->crtc_clock);
> > + limits->link.max_bpp >> 4, adjusted_mode->crtc_clock);
> > }
> >
> > static int
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.h
> > b/drivers/gpu/drm/i915/display/intel_dp.h
> > index 22099de3ca458..a1789419c0d19 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.h
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.h
> > @@ -26,7 +26,14 @@ struct intel_encoder; struct link_config_limits {
> > int min_rate, max_rate;
> > int min_lane_count, max_lane_count;
> > - int min_bpp, max_bpp;
> > + struct {
> > + /* Uncompressed DSC input or link output bpp in 1 bpp units
> */
> > + int min_bpp, max_bpp;
> > + } pipe;
> > + struct {
> > + /* Compressed or uncompressed link output bpp in 1/16 bpp
> units */
> > + int min_bpp, max_bpp;
>
> The 1/16 bpp units is a source of confusion, and I think we should start
> denoting them in naming.
>
> min_bpp_x16, max_bpp_x16
>
> > + } link;
> > };
Also a small question here do we need to track both pipe and link bpp separately
When we can have the helper mentioned above maybe we can call it
pipe_to_link_bpp
Also if it is really required to track link bpp for dsc and non dsc scenario won't it be
Better to have link_dsc and link_non_dsc structs rather than pipe and link since both
are bpp for link with dsc enablement differentiation.
Regards,
Suraj Kandpal
> >
> > void intel_edp_fixup_vbt_bpp(struct intel_encoder *encoder, int
> > pipe_bpp); diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > index 998d8a186cc6f..1809643538d08 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > @@ -156,8 +156,10 @@ static int
> intel_dp_mst_compute_link_config(struct intel_encoder *encoder,
> > &crtc_state->hw.adjusted_mode;
> > int slots = -EINVAL;
> >
> > - slots = intel_dp_mst_find_vcpi_slots_for_bpp(encoder, crtc_state,
> limits->max_bpp,
> > - limits->min_bpp, limits,
> > + slots = intel_dp_mst_find_vcpi_slots_for_bpp(encoder, crtc_state,
> > + limits->link.max_bpp >> 4,
> > + limits->link.min_bpp >> 4,
> > + limits,
> > conn_state, 2 * 3, false);
> >
> > if (slots < 0)
> > @@ -200,8 +202,8 @@ static int
> intel_dp_dsc_mst_compute_link_config(struct intel_encoder *encoder,
> > else
> > dsc_max_bpc = min_t(u8, 10, conn_state-
> >max_requested_bpc);
> >
> > - max_bpp = min_t(u8, dsc_max_bpc * 3, limits->max_bpp);
> > - min_bpp = limits->min_bpp;
> > + max_bpp = min_t(u8, dsc_max_bpc * 3, limits->pipe.max_bpp);
> > + min_bpp = limits->pipe.min_bpp;
> >
> > num_bpc = drm_dp_dsc_sink_supported_input_bpcs(intel_dp-
> >dsc_dpcd,
> > dsc_bpc);
> > @@ -318,7 +320,7 @@ intel_dp_mst_compute_config_limits(struct
> intel_dp *intel_dp,
> > limits->min_lane_count = limits->max_lane_count =
> > intel_dp_max_lane_count(intel_dp);
> >
> > - limits->min_bpp = intel_dp_min_bpp(crtc_state->output_format);
> > + limits->pipe.min_bpp = intel_dp_min_bpp(crtc_state-
> >output_format);
> > /*
> > * FIXME: If all the streams can't fit into the link with
> > * their current pipe_bpp we should reduce pipe_bpp across @@ -
> 327,9
> > +329,12 @@ intel_dp_mst_compute_config_limits(struct intel_dp
> *intel_dp,
> > * MST streams previously. This hack should be removed once
> > * we have the proper retry logic in place.
> > */
> > - limits->max_bpp = min(crtc_state->pipe_bpp, 24);
> > + limits->pipe.max_bpp = min(crtc_state->pipe_bpp, 24);
> >
> > intel_dp_adjust_compliance_config(intel_dp, crtc_state, limits);
> > +
> > + limits->link.min_bpp = limits->pipe.min_bpp << 4;
> > + limits->link.max_bpp = limits->pipe.max_bpp << 4;
> > }
> >
> > static int intel_dp_mst_compute_config(struct intel_encoder *encoder,
>
> --
> Jani Nikula, Intel Open Source Graphics Center
