Hi Stan,
On Fri, 2023-03-24 at 15:51 +0200, Stanislav Lisovskiy wrote:
> According to spec, we should check if output_bpp * pixel_rate is less
> than DDI clock * 72, if UHBR is used.
>
> v2: - s/pipe_config/crtc_state/ (Jani Nikula)
> - Merged previous patch into that one, to remove empty function(Jani Nikula)
>
> v3: - Make that constraint check to be DSC-related only
> - Limit this to only DISPLAY_VER <= 13
>
> HSDES: 1406899791
> BSPEC: 49259
>
> Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/display/intel_dp_mst.c | 29 +++++++++++++++++++--
> 1 file changed, 27 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index a860cbc5dbea..4c0edb760b8e 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -45,6 +45,27 @@
> #include "intel_hotplug.h"
> #include "skl_scaler.h"
>
> +static int intel_dp_mst_check_constraints(struct drm_i915_private *i915, int bpp,
> + const struct drm_display_mode *adjusted_mode,
> + struct intel_crtc_state *crtc_state,
> + bool dsc)
> +{
> + if (intel_dp_is_uhbr(crtc_state) && DISPLAY_VER(i915) <= 13 && dsc) {
> + int output_bpp = bpp;
> + /* DisplayPort 2 128b/132b, bits per lane is always 32 */
> + int symbol_clock = crtc_state->port_clock / 32;
> +
> + if (output_bpp * adjusted_mode->crtc_clock >=
> + symbol_clock * 72) {
> + drm_dbg_kms(&i915->drm, "UHBR check failed(required bw %d available
> %d)\n",
> + output_bpp * adjusted_mode->crtc_clock, symbol_clock * 72);
> + return -EINVAL;
> + }
> + }
> +
> + return 0;
> +}
> +
> static int intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder *encoder,
> struct intel_crtc_state *crtc_state,
> int max_bpp,
> @@ -87,6 +108,10 @@ static int intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder *encoder,
>
> drm_dbg_kms(&i915->drm, "Trying bpp %d\n", bpp);
>
> + ret = intel_dp_mst_check_constraints(i915, bpp, adjusted_mode, crtc_state, dsc);
> + if (ret)
> + continue;
> +
One suggestion, if you move this constraints check to the top of the "for loop", you may be able to
save an unnecessary "drm_dp_calc_pbn_mode" call in case constraints doesn't match for a bpp.
Reviewed-by: Vinod Govindapillai <vinod.govindapillai@xxxxxxxxx>
> slots = drm_dp_atomic_find_time_slots(state, &intel_dp->mst_mgr,
> connector->port,
> crtc_state->pbn);
> @@ -104,8 +129,8 @@ static int intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder *encoder,
> }
> }
>
> - /* Despite slots are non-zero, we still failed the atomic check */
> - if (ret && slots >= 0)
> + /* We failed to find a proper bpp/timeslots, return error */
> + if (ret)
> slots = ret;
>
> if (slots < 0) {
