Re: [Intel-gfx] [PATCH 2/2] drm/i915/dp: Use current cdclk for DSC Bigjoiner BW check

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Mar 29, 2023 at 04:06:21PM +0530, Nautiyal, Ankit K wrote:
> 
> On 3/29/2023 3:27 PM, Ville Syrjälä wrote:
> > On Wed, Mar 29, 2023 at 02:14:49PM +0530, Ankit Nautiyal wrote:
> >> As per Bspec, Big Joiner BW check is:
> >> Output bpp <= PPC * CDCLK frequency * Big joiner interface bits /
> >> Pixel clock
> >>
> >> Currently we always use max_cdclk in the check for both modevalid
> >> and compute config steps.
> >>
> >> During modevalid use max_cdclk_freq for the check.
> >> During compute config step use current cdclk for the check.
> > Nak. cdclk is computed much later based on what is actually needed.
> > The cdclk freq you are using here is essentially a random number.
> 
> Oh I didn't realise that, perhaps I was lucky when I tested this.
> 
> So this check where CDCLK is mentioned, actually expects max_cdclk_freq?
> 
> If it doesnt then, we might have a compressed_bpp value, that might be 
> violating the big joiner bw check.
> 
> Should this be handled while computing cdclk?

Yes. I suggest adding something like intel_vdsc_min_cdclk() that
handles all of it.

> 
> Regards,
> 
> Ankit
> 
> >
> >> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
> >> ---
> >>   drivers/gpu/drm/i915/display/intel_dp.c     | 9 ++++++---
> >>   drivers/gpu/drm/i915/display/intel_dp.h     | 1 +
> >>   drivers/gpu/drm/i915/display/intel_dp_mst.c | 1 +
> >>   3 files changed, 8 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> >> index 3fe651a8f5d0..d6600de1ab49 100644
> >> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> >> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> >> @@ -711,6 +711,7 @@ u32 intel_dp_dsc_nearest_valid_bpp(struct drm_i915_private *i915, u32 bpp, u32 p
> >>   u16 intel_dp_dsc_get_output_bpp(struct drm_i915_private *i915,
> >>   				u32 link_clock, u32 lane_count,
> >>   				u32 mode_clock, u32 mode_hdisplay,
> >> +				unsigned int cdclk,
> >>   				bool bigjoiner,
> >>   				u32 pipe_bpp,
> >>   				u32 timeslots)
> >> @@ -757,9 +758,9 @@ u16 intel_dp_dsc_get_output_bpp(struct drm_i915_private *i915,
> >>   
> >>   	if (bigjoiner) {
> >>   		int bigjoiner_interface_bits = DISPLAY_VER(i915) <= 12 ? 24 : 36;
> >> -		u32 max_bpp_bigjoiner =
> >> -			i915->display.cdclk.max_cdclk_freq * 2 * bigjoiner_interface_bits /
> >> -			intel_dp_mode_to_fec_clock(mode_clock);
> >> +
> >> +		u32 max_bpp_bigjoiner = cdclk * 2 * bigjoiner_interface_bits /
> >> +					intel_dp_mode_to_fec_clock(mode_clock);
> >>   
> >>   		bits_per_pixel = min(bits_per_pixel, max_bpp_bigjoiner);
> >>   	}
> >> @@ -1073,6 +1074,7 @@ intel_dp_mode_valid(struct drm_connector *_connector,
> >>   							    max_lanes,
> >>   							    target_clock,
> >>   							    mode->hdisplay,
> >> +							    dev_priv->display.cdclk.max_cdclk_freq,
> >>   							    bigjoiner,
> >>   							    pipe_bpp, 64) >> 4;
> >>   			dsc_slice_count =
> >> @@ -1580,6 +1582,7 @@ int intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
> >>   							    pipe_config->lane_count,
> >>   							    adjusted_mode->crtc_clock,
> >>   							    adjusted_mode->crtc_hdisplay,
> >> +							    dev_priv->display.cdclk.hw.cdclk,
> >>   							    pipe_config->bigjoiner_pipes,
> >>   							    pipe_bpp,
> >>   							    timeslots);
> >> diff --git a/drivers/gpu/drm/i915/display/intel_dp.h b/drivers/gpu/drm/i915/display/intel_dp.h
> >> index ef39e4f7a329..d150bfe8abf4 100644
> >> --- a/drivers/gpu/drm/i915/display/intel_dp.h
> >> +++ b/drivers/gpu/drm/i915/display/intel_dp.h
> >> @@ -106,6 +106,7 @@ int intel_dp_dsc_compute_bpp(struct intel_dp *intel_dp, u8 dsc_max_bpc);
> >>   u16 intel_dp_dsc_get_output_bpp(struct drm_i915_private *i915,
> >>   				u32 link_clock, u32 lane_count,
> >>   				u32 mode_clock, u32 mode_hdisplay,
> >> +				unsigned int cdclk,
> >>   				bool bigjoiner,
> >>   				u32 pipe_bpp,
> >>   				u32 timeslots);
> >> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> >> index a860cbc5dbea..266e31b78729 100644
> >> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> >> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> >> @@ -925,6 +925,7 @@ intel_dp_mst_mode_valid_ctx(struct drm_connector *connector,
> >>   							    max_lanes,
> >>   							    target_clock,
> >>   							    mode->hdisplay,
> >> +							    dev_priv->display.cdclk.max_cdclk_freq,
> >>   							    bigjoiner,
> >>   							    pipe_bpp, 64) >> 4;
> >>   			dsc_slice_count =
> >> -- 
> >> 2.25.1

-- 
Ville Syrjälä
Intel