[Intel-gfx] [PATCHv2 2/2] i915/display/dp: SDP CRC16 for 128b132b link layer

[Murthy, Arun R]

Any comments?

Thanks and Regards,
Arun R Murthy
--------------------

> -----Original Message-----
> From: Murthy, Arun R <arun.r.murthy at intel.com>
> Sent: Thursday, January 19, 2023 5:17 PM
> To: intel-gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org; Nikula,
> Jani <jani.nikula at intel.com>
> Cc: Murthy, Arun R <arun.r.murthy at intel.com>
> Subject: [PATCHv2 2/2] i915/display/dp: SDP CRC16 for 128b132b link layer
> 
> Enable SDP error detection configuration, this will set CRC16 in 128b/132b
> link layer.
> For Display version 13 a hardware bit31 in register VIDEO_DIP_CTL is added
> to enable/disable SDP CRC applicable for DP2.0 only, but the default value of
> this bit will enable CRC16 in 128b/132b hence skipping this write.
> Corrective actions on SDP corruption is yet to be defined.
> 
> v2: Moved the CRC enable to link training init(Jani N)
> 
> Signed-off-by: Arun R Murthy <arun.r.murthy at intel.com>
> ---
>  .../gpu/drm/i915/display/intel_dp_link_training.c    | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> index 3d3efcf02011..7064e465423b 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> @@ -1453,4 +1453,16 @@ void intel_dp_start_link_train(struct intel_dp
> *intel_dp,
> 
>  	if (!passed)
>  		intel_dp_schedule_fallback_link_training(intel_dp,
> crtc_state);
> +
> +	/* DP v2.0 SCR on SDP CRC16 for 128b/132b Link Layer */
> +	if (intel_dp_is_uhbr(crtc_state) && passed)
> +		drm_dp_dpcd_writeb(&intel_dp->aux,
> +
> DP_SDP_ERROR_DETECTION_CONFIGURATION,
> +				   DP_SDP_CRC16_128B132B_EN);
> +		/*
> +		 * VIDEO_DIP_CTL register bit 31 should be set to '0' to not
> +		 * disable SDP CRC. This is applicable for Display version 13.
> +		 * Default value of bit 31 is '0' hence discarding the write
> +		 */
> +		/* TODO: Corrective actions on SDP corruption yet to be
> defined */
>  }
> --
> 2.25.1