Re: [Intel-gfx] [PATCH 12/12] drm/i915: Parse DP/eDP max lane count from VBT

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 01 Sep 2022, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> On Tue, Jul 19, 2022 at 06:39:29AM -0400, Rodrigo Vivi wrote:
>> On Fri, Jul 15, 2022 at 11:20:44PM +0300, Ville Syrjala wrote:
>> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> > 
>> > Limit the DP lane count based on the new VBT DP/eDP max
>> > lane count field.
>> > 
>> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> > ---
>> >  drivers/gpu/drm/i915/display/intel_bios.c | 16 ++++++++++++++++
>> >  drivers/gpu/drm/i915/display/intel_bios.h |  1 +
>> >  drivers/gpu/drm/i915/display/intel_dp.c   | 13 ++++++++++++-
>> >  3 files changed, 29 insertions(+), 1 deletion(-)
>> > 
>> > diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
>> > index cd86b65055ef..d8063c329b3a 100644
>> > --- a/drivers/gpu/drm/i915/display/intel_bios.c
>> > +++ b/drivers/gpu/drm/i915/display/intel_bios.c
>> > @@ -2489,6 +2489,14 @@ static int _intel_bios_dp_max_link_rate(const struct intel_bios_encoder_data *de
>> >  		return parse_bdb_216_dp_max_link_rate(devdata->child.dp_max_link_rate);
>> >  }
>> >  
>> > +static int _intel_bios_dp_max_lane_count(const struct intel_bios_encoder_data *devdata)
>> > +{
>> > +	if (!devdata || devdata->i915->vbt.version < 244)
>> > +		return 0;
>> > +
>> > +	return devdata->child.dp_max_lane_count + 1;

They just won't learn that non-zero is a really crappy "default" to
set. *sigh*

>> > +}
>> > +
>> >  static void sanitize_device_type(struct intel_bios_encoder_data *devdata,
>> >  				 enum port port)
>> >  {
>> > @@ -3674,6 +3682,14 @@ int intel_bios_dp_max_link_rate(struct intel_encoder *encoder)
>> >  	return _intel_bios_dp_max_link_rate(devdata);
>> >  }
>> >  
>> > +int intel_bios_dp_max_lane_count(struct intel_encoder *encoder)
>> > +{
>> > +	struct drm_i915_private *i915 = to_i915(encoder->base.dev);
>> > +	const struct intel_bios_encoder_data *devdata = i915->vbt.ports[encoder->port];
>> > +
>> > +	return _intel_bios_dp_max_lane_count(devdata);
>> > +}
>> 
>> do we really need 2 functions here since this one is small and we don't have any
>> bit switches and all?!
>> or do you plan to reuse this anywhere else later?
>
> This is modelled after the other similar functions. I think Jani had
> some plans for cleaning up a lot of this stuff, but dunno how far we
> are on that path.

A bit stalled. Eventually I'd like all encoders to have encoder->devdata
and callers would pass that instead of encoder, and we wouldn't have
this i915->vbt.ports[encoder->port]; lookup.

But the first function could be used in print_ddi_port() for printing
the info while the latter couldn't. So I kinda prefer the split.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>


>
>> 
>> > +
>> >  int intel_bios_alternate_ddc_pin(struct intel_encoder *encoder)
>> >  {
>> >  	struct drm_i915_private *i915 = to_i915(encoder->base.dev);
>> > diff --git a/drivers/gpu/drm/i915/display/intel_bios.h b/drivers/gpu/drm/i915/display/intel_bios.h
>> > index e47582b0de0a..e375405a7828 100644
>> > --- a/drivers/gpu/drm/i915/display/intel_bios.h
>> > +++ b/drivers/gpu/drm/i915/display/intel_bios.h
>> > @@ -258,6 +258,7 @@ bool intel_bios_get_dsc_params(struct intel_encoder *encoder,
>> >  int intel_bios_max_tmds_clock(struct intel_encoder *encoder);
>> >  int intel_bios_hdmi_level_shift(struct intel_encoder *encoder);
>> >  int intel_bios_dp_max_link_rate(struct intel_encoder *encoder);
>> > +int intel_bios_dp_max_lane_count(struct intel_encoder *encoder);
>> >  int intel_bios_alternate_ddc_pin(struct intel_encoder *encoder);
>> >  bool intel_bios_port_supports_typec_usb(struct drm_i915_private *i915, enum port port);
>> >  bool intel_bios_port_supports_tbt(struct drm_i915_private *i915, enum port port);
>> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
>> > index 32292c0be2bd..0370c4c105dc 100644
>> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
>> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
>> > @@ -286,11 +286,22 @@ static int intel_dp_max_common_rate(struct intel_dp *intel_dp)
>> >  	return intel_dp_common_rate(intel_dp, intel_dp->num_common_rates - 1);
>> >  }
>> >  
>> > +static int intel_dp_max_source_lane_count(struct intel_digital_port *dig_port)
>> > +{
>> > +	int vbt_max_lanes = intel_bios_dp_max_lane_count(&dig_port->base);
>> > +	int max_lanes = dig_port->max_lanes;
>> > +
>> > +	if (vbt_max_lanes)
>> > +		max_lanes = min(max_lanes, vbt_max_lanes);
>> > +
>> > +	return max_lanes;
>> > +}
>> > +
>> >  /* Theoretical max between source and sink */
>> >  static int intel_dp_max_common_lane_count(struct intel_dp *intel_dp)
>> >  {
>> >  	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
>> > -	int source_max = dig_port->max_lanes;
>> > +	int source_max = intel_dp_max_source_lane_count(dig_port);
>> >  	int sink_max = intel_dp->max_sink_lane_count;
>> >  	int fia_max = intel_tc_port_fia_max_lane_count(dig_port);
>> >  	int lttpr_max = drm_dp_lttpr_max_lane_count(intel_dp->lttpr_common_caps);
>> > -- 
>> > 2.35.1
>> > 

-- 
Jani Nikula, Intel Open Source Graphics Center