Re: [PATCH] drm/i915/icl: remove port A/E lane sharing limitation.

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Jan 30, 2018 at 07:52:14PM +0000, Pandiyan, Dhinakaran wrote:
> 
> On Tue, 2018-01-30 at 14:51 +0530, Mahesh Kumar wrote:
> > From: "Kumar, Mahesh" <mahesh1.kumar@intel.com>
> > 
> > Platforms before Gen11 were sharing lanes between port-A & port-E.
> > This limitation is no more there.
> > 
> > Changes since V1:
> >  - optimize the code (Shashank/Jani)
> >  - create helper function to get max lanes (ville)
> > 
> > Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_ddi.c | 43 +++++++++++++++++-----------------------
> >  1 file changed, 18 insertions(+), 25 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> > index e51559be2e3b..4bde742a8ff4 100644
> > --- a/drivers/gpu/drm/i915/intel_ddi.c
> > +++ b/drivers/gpu/drm/i915/intel_ddi.c
> > @@ -2842,6 +2842,23 @@ static bool intel_ddi_a_force_4_lanes(struct intel_digital_port *dport)
> >  	return false;
> >  }
> >  
> > +static int
> > +intel_ddi_max_lanes(struct drm_i915_private *dev_priv, enum port port)
> > +{
> > +	if (INTEL_GEN(dev_priv) >= 11)
> > +		return 4;
> > +
> > +	if (port == PORT_A || port == PORT_E) {
> > +		if (I915_READ(DDI_BUF_CTL(PORT_A)) & DDI_A_4_LANES)
> 
> 
> Is the expectation that bios has already written the correct value
> depending on the board?

We have a fixup later on for BIOS fails. Might be nice to try and
pull that in as well so that we would have all the logic in one
clear place.

> 
> The patch itself looks correct 
> Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> 
> 
> 
> > +			return port == PORT_A ? 4 : 0;
> > +		else
> > +			/* Both A and E share 2 lanes */
> > +			return 2;
> > +	}
> > +
> > +	return 4;
> > +}
> > +
> >  void intel_ddi_init(struct drm_i915_private *dev_priv, enum port port)
> >  {
> >  	struct intel_digital_port *intel_dig_port;
> > @@ -2850,31 +2867,7 @@ void intel_ddi_init(struct drm_i915_private *dev_priv, enum port port)
> >  	bool init_hdmi, init_dp, init_lspcon = false;
> >  	int max_lanes;
> >  
> > -	if (I915_READ(DDI_BUF_CTL(PORT_A)) & DDI_A_4_LANES) {
> > -		switch (port) {
> > -		case PORT_A:
> > -			max_lanes = 4;
> > -			break;
> > -		case PORT_E:
> > -			max_lanes = 0;
> > -			break;
> > -		default:
> > -			max_lanes = 4;
> > -			break;
> > -		}
> > -	} else {
> > -		switch (port) {
> > -		case PORT_A:
> > -			max_lanes = 2;
> > -			break;
> > -		case PORT_E:
> > -			max_lanes = 2;
> > -			break;
> > -		default:
> > -			max_lanes = 4;
> > -			break;
> > -		}
> > -	}
> > +	max_lanes = intel_ddi_max_lanes(dev_priv, port);
> >  
> >  	init_hdmi = (dev_priv->vbt.ddi_port_info[port].supports_dvi ||
> >  		     dev_priv->vbt.ddi_port_info[port].supports_hdmi);
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-- 
Ville Syrjälä
Intel OTC
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