Re: [PATCH v2 6/6] drm/i915: Set DP min_bpp to 8*3 for non-RGB output formats

["Sripada, Radhakrishna" <radhakrishna.sripada@intel.com>]

On Thu, 2019-04-11 at 21:27 +0300, Ville Syrjälä wrote:
> On Tue, Apr 09, 2019 at 02:04:01PM -0700, Dhinakaran Pandiyan wrote:
> > On Tue, 2019-04-09 at 23:38 +0300, Ville Syrjälä wrote:
> > > On Tue, Apr 09, 2019 at 01:28:18PM -0700, Dhinakaran Pandiyan
> > > wrote:
> > > > On Tue, 2019-03-26 at 16:25 +0200, Ville Syrjala wrote:
> > > > > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > > > 
> > > > > 6bpc is only legal for RGB and RAW pixel encodings. For the
> > > > > rest
> > > > > the minimum is 8bpc. Set our lower limit accordingly.
> > > > 
> > > > Patch doesn't apply anymore, got a conflict in intel_drv.h. 
> > > > 
> > > > 
> > > > > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > > > ---
> > > > >  drivers/gpu/drm/i915/intel_dp.c     | 10 +++++++++-
> > > > >  drivers/gpu/drm/i915/intel_dp_mst.c |  2 +-
> > > > >  drivers/gpu/drm/i915/intel_drv.h    |  1 +
> > > > >  3 files changed, 11 insertions(+), 2 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/gpu/drm/i915/intel_dp.c
> > > > > b/drivers/gpu/drm/i915/intel_dp.c
> > > > > index 2aee526ed632..149fdfbcb343 100644
> > > > > --- a/drivers/gpu/drm/i915/intel_dp.c
> > > > > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > > > > @@ -2002,6 +2002,14 @@ static int
> > > > > intel_dp_dsc_compute_config(struct
> > > > > intel_dp
> > > > > *intel_dp,
> > > > >  	return 0;
> > > > >  }
> > > > >  
> > > > > +int intel_dp_min_bpp(const struct intel_crtc_state
> > > > > *crtc_state)
> > > > > +{
> > > > > +	if (crtc_state->output_format ==
> > > > > INTEL_OUTPUT_FORMAT_RGB)
> > > > > +		return 6 * 3;
> > > > > +	else
> > > > > +		return 8 * 3;
> > > > 
> > > > Code matches spec, however I think there is a possibility of
> > > > min_bpp
> > > > becoming
> > > > greater than max_bpp. The max_bpc property allows user space to
> > > > set a value
> > > > of 6
> > > > and limits.min_bpp can become 24 because of the code above. Add
> > > > a check for
> > > > that
> > > > in compute_link_config()? Probably would mess up the
> > > > compute_config() loop
> > > > too.
> > > 
> > > The code looks correct. Ie. should just end up with -EINVAL.
> > 
> > Yup, it does now as I read it carefully again :)
> > Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> 
> Ta. Pushed.
Late on jumping the train but dont we have to limit the range exposed
while attaching the "max bpc" as well in this case?

- Radhakrishna(RK) Sripada
> 
> > 
> > However, I don't like the fact we are hiding the detail that
> > min_bpp can be >
> > max_bpp. If someone decides add a link config optimization starting
> > from
> > min_bpp, it's easy to miss this detail. 
> 
> I guess I wouldn't object to an explicit check for this. As a bonus
> we could add a more descriptive debug message for this case.
> 
> > 
> > -DK
> > 
> > > 
> > > > 
> > > > 
> > > > > +}
> > > > > +
> > > > >  static int
> > > > >  intel_dp_compute_link_config(struct intel_encoder *encoder,
> > > > >  			     struct intel_crtc_state
> > > > > *pipe_config,
> > > > > @@ -2025,7 +2033,7 @@ intel_dp_compute_link_config(struct
> > > > > intel_encoder
> > > > > *encoder,
> > > > >  	limits.min_lane_count = 1;
> > > > >  	limits.max_lane_count =
> > > > > intel_dp_max_lane_count(intel_dp);
> > > > >  
> > > > > -	limits.min_bpp = 6 * 3;
> > > > > +	limits.min_bpp = intel_dp_min_bpp(pipe_config);
> > > > >  	limits.max_bpp = intel_dp_compute_bpp(intel_dp,
> > > > > pipe_config);
> > > > >  
> > > > >  	if (intel_dp_is_edp(intel_dp) && intel_dp->edp_dpcd[0]
> > > > > < DP_EDP_14) {
> > > > > diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c
> > > > > b/drivers/gpu/drm/i915/intel_dp_mst.c
> > > > > index 6d2af7cf48e6..79c229184873 100644
> > > > > --- a/drivers/gpu/drm/i915/intel_dp_mst.c
> > > > > +++ b/drivers/gpu/drm/i915/intel_dp_mst.c
> > > > > @@ -119,7 +119,7 @@ static int
> > > > > intel_dp_mst_compute_config(struct
> > > > > intel_encoder *encoder,
> > > > >  	limits.min_lane_count =
> > > > >  	limits.max_lane_count =
> > > > > intel_dp_max_lane_count(intel_dp);
> > > > >  
> > > > > -	limits.min_bpp = 6 * 3;
> > > > > +	limits.min_bpp = intel_dp_min_bpp(pipe_config);
> > > > >  	limits.max_bpp = pipe_config->pipe_bpp;
> > > > >  
> > > > >  	intel_dp_adjust_compliance_config(intel_dp,
> > > > > pipe_config, &limits);
> > > > > diff --git a/drivers/gpu/drm/i915/intel_drv.h
> > > > > b/drivers/gpu/drm/i915/intel_drv.h
> > > > > index e79954c6271c..13f1b0367287 100644
> > > > > --- a/drivers/gpu/drm/i915/intel_drv.h
> > > > > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > > > > @@ -1919,6 +1919,7 @@ void
> > > > > intel_dp_adjust_compliance_config(struct
> > > > > intel_dp
> > > > > *intel_dp,
> > > > >  				       struct
> > > > > link_config_limits *limits);
> > > > >  bool intel_dp_limited_color_range(const struct
> > > > > intel_crtc_state
> > > > > *crtc_state,
> > > > >  				  const struct
> > > > > drm_connector_state *conn_state);
> > > > > +int intel_dp_min_bpp(const struct intel_crtc_state
> > > > > *crtc_state);
> > > > >  bool intel_dp_port_enabled(struct drm_i915_private
> > > > > *dev_priv,
> > > > >  			   i915_reg_t dp_reg, enum port port,
> > > > >  			   enum pipe *pipe);
> > > 
> > > 
> 
> 
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