[Intel-gfx] [PATCH 3/4] drm/i915: Remove DP_PORT_EN stuff from link training code

[Imre Deak]

On Thu, Sep 30, 2021 at 07:19:06PM +0300, Imre Deak wrote:
> On Thu, Sep 30, 2021 at 07:16:10PM +0300, Ville Syrjälä wrote:
> > On Thu, Sep 30, 2021 at 07:09:03PM +0300, Imre Deak wrote:
> > > On Thu, Sep 30, 2021 at 04:43:09PM +0300, Ville Syrjala wrote:
> > > > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > > > 
> > > > Setting DP_PORT_EN in intel_dp->DP is already handled by
> > > > intel_dp_enable_port() so there is no point in setting it also
> > > > from the link training code.
> > > > 
> > > > For DDI platforms a bit with that name doesn't even exist. The
> > > > counterpart is DDI_BUF_CTL_ENABLE, which is already set up by
> > > > intel_ddi_prepare_link_retrain(). Fortunately it is the same bit
> > > > so there was no harm in doing this from the platform independent
> > > > code as well. But it's just confusing when platform independent
> > > > code sets platform specific bits in intel_dp->DP. Just get rid
> > > > of it.
> > > > 
> > > > Cc: Imre Deak <imre.deak at intel.com>
> > > > Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > > 
> > > Reviewed-by: Imre Deak <imre.deak.intel.com>
> > > 
> > > On pre-DDI platforms intel_dp_enable_port() may not be called before
> > > short HPD/link-retraining, but the init/resume time HW readout will
> > > set DP_PORT_EN for that case.
> > 
> > I actually wonder what happens on DDI platforms. We don't do the resume
> > readout there AFAICS, so if link retraining happens before any modesets
> > are we just screwed atm?
> 
> Yea.

It's unlikely to cause a problem though, since resume mostly happens
with disabled outputs?

> 
> > 
> > > 
> > > > ---
> > > >  drivers/gpu/drm/i915/display/intel_dp_link_training.c | 2 --
> > > >  1 file changed, 2 deletions(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> > > > index 449499a5c4c1..053ed9302cda 100644
> > > > --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> > > > +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> > > > @@ -499,8 +499,6 @@ intel_dp_prepare_link_train(struct intel_dp *intel_dp,
> > > >  		DP_SET_ANSI_128B132B : DP_SET_ANSI_8B10B;
> > > >  	drm_dp_dpcd_write(&intel_dp->aux, DP_DOWNSPREAD_CTRL, link_config, 2);
> > > >  
> > > > -	intel_dp->DP |= DP_PORT_EN;
> > > > -
> > > >  	return true;
> > > >  }
> > > >  
> > > > -- 
> > > > 2.32.0
> > > > 
> > 
> > -- 
> > Ville Syrjälä
> > Intel