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

[Jani Nikula]

On Thu, 08 Dec 2016, Manasi Navare <manasi.d.navare at intel.com> wrote:
> Daniel, can we merge this patch?

Pushed this one to dinq, thanks for the patch.

BR,
Jani.


> 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

-- 
Jani Nikula, Intel Open Source Technology Center