Re: [v6 2/4] drm/i915/fec: Set FEC_READY in FEC_CONFIGURATION

[Manasi Navare <manasi.d.navare@intel.com>]

On Tue, Nov 06, 2018 at 04:51:22PM +0200, Ville Syrjälä wrote:
> On Mon, Nov 05, 2018 at 04:48:57PM -0800, Manasi Navare wrote:
> > On Mon, Nov 05, 2018 at 03:31:48PM -0800, Anusha Srivatsa wrote:
> > > If the panel supports FEC, the driver has to
> > > set the FEC_READY bit in the dpcd register:
> > > FEC_CONFIGURATION.
> > > 
> > > This has to happen before link training.
> > > 
> > > v2: s/intel_dp_set_fec_ready/intel_dp_sink_set_fec_ready
> > >    - change commit message. (Gaurav)
> > > 
> > > v3: rebased. (r-b Manasi)
> > > 
> > > v4: Use fec crtc state, before setting FEC_READY
> > > bit. (Anusha)
> > > 
> > > v5: Move to intel_ddi.c
> > > - Make the function static (Anusha)
> > > 
> > > Cc: dri-devel@lists.freedesktop.org
> > > Cc: Gaurav K Singh <gaurav.k.singh@intel.com>
> > > Cc: Jani Nikula <jani.nikula@linux.intel.com>
> > > Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> > > Cc: Manasi Navare <manasi.d.navare@intel.com>
> > > Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/intel_ddi.c | 15 +++++++++++++++
> > >  1 file changed, 15 insertions(+)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> > > index 46c1b9e12fbd..53a9b31e66a2 100644
> > > --- a/drivers/gpu/drm/i915/intel_ddi.c
> > > +++ b/drivers/gpu/drm/i915/intel_ddi.c
> > > @@ -3051,6 +3051,20 @@ static void icl_program_mg_dp_mode(struct intel_digital_port *intel_dig_port)
> > >  	I915_WRITE(MG_DP_MODE(port, 1), ln1);
> > >  }
> > >  
> > > +static void intel_dp_sink_set_fec_ready(struct intel_dp *intel_dp,
> > > +					const struct intel_crtc_state *crtc_state,
> > > +					int state)
> > 
> > u8 state should be good enough since you are writing only a byte here
> 
> AFAICS this is never called with anything but DP_FEC_READY. So
> there is absolutely benefit in making the caller have to
> pass that in. Just drop the 'state' argument entirely IMO.

Oh yes thats correct, its a constant at DRM level and can be used directly since state never really gets set to
DP_FEC_NOT_READy. 

Manasi

> 
> > 
> > > +{
> > > +	int ret;
> > > +
> > > +	if (!crtc_state->fec_enable)
> > > +		return;
> > > +
> > > +	ret = drm_dp_dpcd_writeb(&intel_dp->aux, DP_FEC_CONFIGURATION, state);
> > > +	if (ret < 0)
> > 
> > This should ret <=0 since even if it writes 0 bytes its an error. Infact you dont need ret
> > you can just say"
> > if (drm_dp_dpcd_writeb(&intel_dp->aux, DP_FEC_CONFIGURATION, state) <= 0)
> > 
> > After the above changes,
> > 
> > Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
> > 
> > Manasi
> > > +		DRM_DEBUG_KMS("Failed to get FEC enabled in sink\n");
> 
> This debug msg doesn't make sense.
> 
> > > +}
> > > +
> > >  static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
> > >  				    const struct intel_crtc_state *crtc_state,
> > >  				    const struct drm_connector_state *conn_state)
> > > @@ -3091,6 +3105,7 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
> > >  		intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
> > >  	intel_dp_sink_set_decompression_state(intel_dp, crtc_state,
> > >  					      true);
> > > +	intel_dp_sink_set_fec_ready(intel_dp, crtc_state, DP_FEC_READY);
> > >  	intel_dp_start_link_train(intel_dp);
> > >  	if (port != PORT_A || INTEL_GEN(dev_priv) >= 9)
> > >  		intel_dp_stop_link_train(intel_dp);
> > > -- 
> > > 2.19.1
> > > 
> 
> -- 
> Ville Syrjälä
> Intel
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