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

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

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@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@linux.intel.com>

>  	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
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