[Intel-gfx] [PATCH] drm/i915/display: Handle lane polarity for DDI port

[Shankar, Uma]

> -----Original Message-----
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Sent: Thursday, February 11, 2021 6:33 PM
> To: Shankar, Uma <uma.shankar at intel.com>
> Cc: intel-gfx at lists.freedesktop.org; Souza, Jose <jose.souza at intel.com>; Roper,
> Matthew D <matthew.d.roper at intel.com>
> Subject: Re: [PATCH] drm/i915/display: Handle lane polarity for DDI port
> 
> On Thu, Feb 11, 2021 at 05:12:09PM +0530, Uma Shankar wrote:
> > Lane Reversal is required for some of the DDI ports. This information
> > is populated in VBT and driver should read the same and set the
> > polarity while enabling the port. This patch handles the same.
> >
> > It helps fix a display blankout issue on DP ports on certain
> > platforms.
> >
> > Signed-off-by: Uma Shankar <uma.shankar at intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_bios.c | 17 +++++++++++++++++
> > drivers/gpu/drm/i915/display/intel_bios.h |  2 ++
> > drivers/gpu/drm/i915/display/intel_ddi.c  |  3 +++
> >  3 files changed, 22 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_bios.c
> > b/drivers/gpu/drm/i915/display/intel_bios.c
> > index 7118530a1c38..dd51413e7f45 100644
> > --- a/drivers/gpu/drm/i915/display/intel_bios.c
> > +++ b/drivers/gpu/drm/i915/display/intel_bios.c
> > @@ -2674,6 +2674,23 @@ intel_bios_is_lspcon_present(const struct
> drm_i915_private *i915,
> >  	return HAS_LSPCON(i915) && child && child->lspcon;  }
> >
> > +/**
> > + * intel_bios_is_lane_reversal_needed - if lane reversal needed on port
> > + * @i915:       i915 device instance
> > + * @port:       port to check
> > + *
> > + * Return true if port requires lane reversal  */ bool
> > +intel_bios_is_lane_reversal_needed(const struct drm_i915_private *i915,
> > +				   enum port port)
> > +{
> > +	const struct child_device_config *child =
> > +		i915->vbt.ddi_port_info[port].child;
> > +
> > +	return child && child->lane_reversal; }
> > +
> >  enum aux_ch intel_bios_port_aux_ch(struct drm_i915_private *dev_priv,
> >  				   enum port port)
> >  {
> > diff --git a/drivers/gpu/drm/i915/display/intel_bios.h
> > b/drivers/gpu/drm/i915/display/intel_bios.h
> > index e29e79faa01b..f25190ecfe97 100644
> > --- a/drivers/gpu/drm/i915/display/intel_bios.h
> > +++ b/drivers/gpu/drm/i915/display/intel_bios.h
> > @@ -241,6 +241,8 @@ bool intel_bios_is_port_hpd_inverted(const struct
> drm_i915_private *i915,
> >  				     enum port port);
> >  bool intel_bios_is_lspcon_present(const struct drm_i915_private *i915,
> >  				  enum port port);
> > +bool intel_bios_is_lane_reversal_needed(const struct drm_i915_private *i915,
> > +					enum port port);
> >  enum aux_ch intel_bios_port_aux_ch(struct drm_i915_private *dev_priv,
> > enum port port);  bool intel_bios_get_dsc_params(struct intel_encoder *encoder,
> >  			       struct intel_crtc_state *crtc_state, diff --git
> > a/drivers/gpu/drm/i915/display/intel_ddi.c
> > b/drivers/gpu/drm/i915/display/intel_ddi.c
> > index 3c4003605f93..2d6906f6995f 100644
> > --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> > +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> > @@ -4082,6 +4082,9 @@ void intel_ddi_init(struct drm_i915_private *dev_priv,
> enum port port)
> >  			intel_de_read(dev_priv, DDI_BUF_CTL(port))
> >  			& (DDI_BUF_PORT_REVERSAL | DDI_A_4_LANES);
> >
> > +	if (intel_bios_is_lane_reversal_needed(dev_priv, port))
> > +		dig_port->saved_port_bits |= DDI_BUF_PORT_REVERSAL;
> > +
> 
> Not a huge fan of saved_port_bits in general but as long as we have it stuffing this in
> there seems like the best option.
> 
> Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

Pushed the change to drm-intel-next. Thanks Ville for the review.

Regards,
Uma Shankar
> >  	dig_port->dp.output_reg = INVALID_MMIO_REG;
> >  	dig_port->max_lanes = intel_ddi_max_lanes(dig_port);
> >  	dig_port->aux_ch = intel_bios_port_aux_ch(dev_priv, port);
> > --
> > 2.26.2
> 
> --
> Ville Syrjälä
> Intel