Re: [PATCH v5 1/3] drm/i915: Disable fast link training if DP config changes

[Mika Kahola <mika.kahola@intel.com>]

On Mon, 2016-01-04 at 18:42 +0200, Ville Syrjälä wrote:
> On Mon, Jan 04, 2016 at 01:21:22PM +0200, Mika Kahola wrote:
> > Disable DP link training optimization if DP link configuration
> > changes. If one of the DP link parameters i.e. link rate or
> > lane count changes the link training does no longer apply the
> > previously computed drive current and pre-emphasis level.
> > Instead, the link training is started with zero values.
> > 
> > v5: Commit message update. Split the original patch in two.
> >     This part considers only changes on link configuration.
> >     Removed unnecessary debug messages. (Ville)
> > 
> > v4: Parameter and debug message naming improvements.
> >     Fix for link parameter check (Ville)
> > 
> > v3: Remove cached old link parameters. Instead, disable
> >     fast link training feature when link parameters are
> >     set (Ville)
> > 
> > v2: Readout DPCD register to check if no aux handshaking is
> >     required in link training (Ander)
> > 
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91393
> > Signed-off-by: Mika Kahola <mika.kahola@intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_dp.c               | 5 +++++
> >  drivers/gpu/drm/i915/intel_dp_link_training.c | 3 +++
> >  2 files changed, 8 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index 796e3d3..6b36d82 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -1676,6 +1676,11 @@ found:
> >  void intel_dp_set_link_params(struct intel_dp *intel_dp,
> >  			      const struct intel_crtc_state *pipe_config)
> >  {
> > +	if (intel_dp->link_rate != pipe_config->port_clock ||
> > +	    intel_dp->lane_count != pipe_config->lane_count) {
> > +		intel_dp->train_set_valid = false;
> > +	}
> > +
> >  	intel_dp->link_rate = pipe_config->port_clock;
> >  	intel_dp->lane_count = pipe_config->lane_count;
> >  }
> > diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > index 8888793..59d59be 100644
> > --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> > +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > @@ -85,6 +85,9 @@ static bool
> >  intel_dp_reset_link_train(struct intel_dp *intel_dp,
> >  			uint8_t dp_train_pat)
> >  {
> > +	DRM_DEBUG_KMS("link training optimization: %s\n",
> > +		      intel_dp->train_set_valid ? "true" : "false");
> 
> yesno(intel_dp->train_set_valid)
> 
> With that
> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
Thanks for the review!

Cheers,
Mika

> > +
> >  	if (!intel_dp->train_set_valid)
> >  		memset(intel_dp->train_set, 0, sizeof(intel_dp->train_set));
> >  	intel_dp_set_signal_levels(intel_dp);
> > -- 
> > 1.9.1
> 


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