[PATCH 2/4] drm/i915: Compute sink's max lane count/link BW at Hotplug

[Manasi Navare]

Daniel, can we merge this patch?
It has no dependency on other link train patches,
it is just a clean up for the existing driver code that
uses max link rate and lane count values.
Other link train patches have dependency on this thats why
it was part of the series.
But it would be great if this gets merged so that i dont have to
rebase it tremendously after 3 weeks when I am back and plus
its good for the driver to start using this clean up. This kind
of clean up was long due.

Regards
Manasi

On Thu, Dec 08, 2016 at 11:23:39PM +0200, Jani Nikula wrote:
> On Tue, 06 Dec 2016, Manasi Navare <manasi.d.navare at intel.com> wrote:
> > Sink's capabilities are advertised through DPCD registers and get
> > updated only on hotplug. So they should be computed only once in the
> > long pulse handler and saved off in intel_dp structure for the use
> > later. For this reason two new fields max_sink_lane_count and
> > max_sink_link_bw are added to intel_dp structure.
> >
> > This also simplifies the fallback link rate/lane count logic
> > to handle link training failure. In that case, the max_sink_link_bw
> > and max_sink_lane_count can be reccomputed to match the fallback
> > values lowering the sink capabilities due to link train failure.
> >
> > Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
> > Cc: Jani Nikula <jani.nikula at linux.intel.com>
> > Cc: Daniel Vetter <daniel.vetter at intel.com>
> > Signed-off-by: Manasi Navare <manasi.d.navare at intel.com>
> 
> Reviewed-by: Jani Nikula <jani.nikula at intel.com>
> 
> Eventually we may want to call the fields *link* rates, because that's
> what they'll effectively be. Transient values that don't reflect the
> sink or source capabilities, but the link capabilities.
> 
> > ---
> >  drivers/gpu/drm/i915/intel_dp.c  | 10 ++++++++--
> >  drivers/gpu/drm/i915/intel_drv.h |  4 ++++
> >  2 files changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index db75bb9..434dc7d 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -156,7 +156,7 @@ static u8 intel_dp_max_lane_count(struct intel_dp *intel_dp)
> >  	u8 source_max, sink_max;
> >  
> >  	source_max = intel_dig_port->max_lanes;
> > -	sink_max = drm_dp_max_lane_count(intel_dp->dpcd);
> > +	sink_max = intel_dp->max_sink_lane_count;
> >  
> >  	return min(source_max, sink_max);
> >  }
> > @@ -213,7 +213,7 @@ static u8 intel_dp_max_lane_count(struct intel_dp *intel_dp)
> >  
> >  	*sink_rates = default_rates;
> >  
> > -	return (intel_dp_max_link_bw(intel_dp) >> 3) + 1;
> > +	return (intel_dp->max_sink_link_bw >> 3) + 1;
> >  }
> >  
> >  static int
> > @@ -4395,6 +4395,12 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
> >  		      yesno(intel_dp_source_supports_hbr2(intel_dp)),
> >  		      yesno(drm_dp_tps3_supported(intel_dp->dpcd)));
> >  
> > +	/* Set the max lane count for sink */
> > +	intel_dp->max_sink_lane_count = drm_dp_max_lane_count(intel_dp->dpcd);
> > +
> > +	/* Set the max link BW for sink */
> > +	intel_dp->max_sink_link_bw = intel_dp_max_link_bw(intel_dp);
> > +
> >  	intel_dp_print_rates(intel_dp);
> >  
> >  	intel_dp_read_desc(intel_dp);
> > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> > index fd77a3b..b6526ad 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -906,6 +906,10 @@ struct intel_dp {
> >  	/* sink rates as reported by DP_SUPPORTED_LINK_RATES */
> >  	uint8_t num_sink_rates;
> >  	int sink_rates[DP_MAX_SUPPORTED_RATES];
> > +	/* Max lane count for the sink as per DPCD registers */
> > +	uint8_t max_sink_lane_count;
> > +	/* Max link BW for the sink as per DPCD registers */
> > +	int max_sink_link_bw;
> >  	/* sink or branch descriptor */
> >  	struct intel_dp_desc desc;
> >  	struct drm_dp_aux aux;
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center