[PATCHv4 2/2] i915/display/dp: SDP CRC16 for 128b132b link layer

[Jani Nikula]

On Thu, 02 Mar 2023, Arun R Murthy <arun.r.murthy at intel.com> wrote:
> 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)
> v3: Moved crc enable to ddi pre enable <Jani N>
> v4: Separate function for SDP CRC16 (Jani N)
>
> Signed-off-by: Arun R Murthy <arun.r.murthy at intel.com>

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

> ---
>  drivers/gpu/drm/i915/display/intel_ddi.c      |  4 ++++
>  .../drm/i915/display/intel_dp_link_training.c | 20 +++++++++++++++++++
>  .../drm/i915/display/intel_dp_link_training.h |  2 ++
>  3 files changed, 26 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> index e5979427b38b..127b3035f92d 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -2519,6 +2519,10 @@ static void intel_ddi_pre_enable_dp(struct intel_atomic_state *state,
>  {
>  	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
>  
> +	if (HAS_DP20(dev_priv))
> +		intel_dp_128b132b_sdp_crc16(enc_to_intel_dp(encoder),
> +					    crtc_state);
> +
>  	if (DISPLAY_VER(dev_priv) >= 12)
>  		tgl_ddi_pre_enable_dp(state, encoder, crtc_state, conn_state);
>  	else
> 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..35d31e4efab9 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> @@ -1454,3 +1454,23 @@ void intel_dp_start_link_train(struct intel_dp *intel_dp,
>  	if (!passed)
>  		intel_dp_schedule_fallback_link_training(intel_dp, crtc_state);
>  }
> +
> +void intel_dp_128b132b_sdp_crc16(struct intel_dp *intel_dp,
> +				 const struct intel_crtc_state *crtc_state)
> +{
> +	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> +
> +	/*
> +	 * 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
> +	 */
> +	if (intel_dp_is_uhbr(crtc_state))
> +		/* DP v2.0 SCR on SDP CRC16 for 128b/132b Link Layer */
> +		drm_dp_dpcd_writeb(&intel_dp->aux,
> +				   DP_SDP_ERROR_DETECTION_CONFIGURATION,
> +				   DP_SDP_CRC16_128B132B_EN);
> +
> +	drm_dbg_kms(&i915->drm, "DP2.0 SDP CRC16 for 128b/132b enabled\n");
> +}
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.h b/drivers/gpu/drm/i915/display/intel_dp_link_training.h
> index 7fa1c0833096..2c8f2775891b 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.h
> +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.h
> @@ -39,4 +39,6 @@ static inline u8 intel_dp_training_pattern_symbol(u8 pattern)
>  	return pattern & ~DP_LINK_SCRAMBLING_DISABLE;
>  }
>  
> +void intel_dp_128b132b_sdp_crc16(struct intel_dp *intel_dp,
> +				 const struct intel_crtc_state *crtc_state);
>  #endif /* __INTEL_DP_LINK_TRAINING_H__ */

-- 
Jani Nikula, Intel Open Source Graphics Center