Re: [Intel-gfx] [PATCH 18/29] drm/i915/dp: Wait for FEC detected status in the sink

["Lisovskiy, Stanislav" <stanislav.lisovskiy@intel.com>]

On Tue, Oct 24, 2023 at 04:09:14AM +0300, Imre Deak wrote:
> As required by the DP standard wait for the sink to detect the FEC
> decode enabling symbol sent by the source.
> 
> Signed-off-by: Imre Deak <imre.deak@intel.com>

Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>

> ---
>  drivers/gpu/drm/i915/display/intel_ddi.c    | 73 +++++++++++++++++++++
>  drivers/gpu/drm/i915/display/intel_ddi.h    |  3 +
>  drivers/gpu/drm/i915/display/intel_dp_mst.c |  4 ++
>  3 files changed, 80 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> index dac3b59758af7..6f9d0f2ff3d9a 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -25,6 +25,7 @@
>   *
>   */
>  
> +#include <linux/iopoll.h>
>  #include <linux/string_helpers.h>
>  
>  #include <drm/display/drm_scdc_helper.h>
> @@ -2220,6 +2221,74 @@ static void intel_dp_sink_set_fec_ready(struct intel_dp *intel_dp,
>  	if (drm_dp_dpcd_writeb(&intel_dp->aux, DP_FEC_CONFIGURATION, DP_FEC_READY) <= 0)
>  		drm_dbg_kms(&i915->drm,
>  			    "Failed to set FEC_READY in the sink\n");
> +
> +	if (drm_dp_dpcd_writeb(&intel_dp->aux, DP_FEC_STATUS,
> +			       DP_FEC_DECODE_EN_DETECTED | DP_FEC_DECODE_DIS_DETECTED) <= 0)
> +		drm_dbg_kms(&i915->drm, "Failed to clear FEC detected flags\n");
> +}
> +
> +static int read_fec_detected_status(struct drm_dp_aux *aux)
> +{
> +	int ret;
> +	u8 status;
> +
> +	ret = drm_dp_dpcd_readb(aux, DP_FEC_STATUS, &status);
> +	if (ret < 0)
> +		return ret;
> +
> +	return status;
> +}
> +
> +static void wait_for_fec_detected(struct drm_dp_aux *aux, bool enabled)
> +{
> +	struct drm_i915_private *i915 = to_i915(aux->drm_dev);
> +	int mask = enabled ? DP_FEC_DECODE_EN_DETECTED : DP_FEC_DECODE_DIS_DETECTED;
> +	int status;
> +	int err;
> +
> +	err = readx_poll_timeout(read_fec_detected_status, aux, status,
> +				 status & mask || status < 0,
> +				 10000, 200000);
> +
> +	if (!err && status >= 0)
> +		return;
> +
> +	if (err == -ETIMEDOUT)
> +		drm_err(&i915->drm, "Timeout waiting for FEC %s to get detected\n",
> +			str_enabled_disabled(enabled));
> +	else
> +		drm_dbg_kms(&i915->drm, "FEC detected status read error: %d\n", status);
> +}
> +
> +void intel_ddi_wait_for_fec_status(struct intel_encoder *encoder,
> +				   const struct intel_crtc_state *crtc_state,
> +				   bool enabled)
> +{
> +	struct drm_i915_private *i915 = to_i915(crtc_state->uapi.crtc->dev);
> +	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> +	int ret;
> +
> +	if (!crtc_state->fec_enable)
> +		return;
> +
> +	if (enabled)
> +		ret = intel_de_wait_for_set(i915, dp_tp_status_reg(encoder, crtc_state),
> +					    DP_TP_STATUS_FEC_ENABLE_LIVE, 1);
> +	else
> +		ret = intel_de_wait_for_clear(i915, dp_tp_status_reg(encoder, crtc_state),
> +					      DP_TP_STATUS_FEC_ENABLE_LIVE, 1);
> +
> +	if (ret)
> +		drm_err(&i915->drm,
> +			"Timeout waiting for FEC live state to get %s\n",
> +			str_enabled_disabled(enabled));
> +
> +	/*
> +	 * At least the Synoptics MST hub doesn't set the detected flag for
> +	 * FEC decoding disabling so skip waiting for that.
> +	 */
> +	if (enabled)
> +		wait_for_fec_detected(&intel_dp->aux, enabled);
>  }
>  
>  static void intel_ddi_enable_fec(struct intel_encoder *encoder,
> @@ -2887,6 +2956,8 @@ static void intel_disable_ddi_buf(struct intel_encoder *encoder,
>  	} else {
>  		disable_ddi_buf(encoder, crtc_state);
>  	}
> +
> +	intel_ddi_wait_for_fec_status(encoder, crtc_state, false);
>  }
>  
>  static void intel_ddi_post_disable_dp(struct intel_atomic_state *state,
> @@ -3248,6 +3319,8 @@ static void intel_enable_ddi(struct intel_atomic_state *state,
>  	if (!intel_crtc_is_bigjoiner_slave(crtc_state))
>  		intel_ddi_enable_transcoder_func(encoder, crtc_state);
>  
> +	intel_ddi_wait_for_fec_status(encoder, crtc_state, true);
> +
>  	/* Enable/Disable DP2.0 SDP split config before transcoder */
>  	intel_audio_sdp_split_update(crtc_state);
>  
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.h b/drivers/gpu/drm/i915/display/intel_ddi.h
> index 4999c0ee229bd..e939b93fc81c2 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.h
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.h
> @@ -60,6 +60,9 @@ void intel_ddi_disable_transcoder_func(const struct intel_crtc_state *crtc_state
>  void intel_ddi_enable_transcoder_clock(struct intel_encoder *encoder,
>  				       const struct intel_crtc_state *crtc_state);
>  void intel_ddi_disable_transcoder_clock(const  struct intel_crtc_state *crtc_state);
> +void intel_ddi_wait_for_fec_status(struct intel_encoder *encoder,
> +				   const struct intel_crtc_state *crtc_state,
> +				   bool enabled);
>  void intel_ddi_set_dp_msa(const struct intel_crtc_state *crtc_state,
>  			  const struct drm_connector_state *conn_state);
>  bool intel_ddi_connector_get_hw_state(struct intel_connector *intel_connector);
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index b7a9ce40cf59a..a1ea75cd5ea84 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -853,6 +853,7 @@ static void intel_mst_enable_dp(struct intel_atomic_state *state,
>  	struct drm_dp_mst_topology_state *mst_state =
>  		drm_atomic_get_new_mst_topology_state(&state->base, &intel_dp->mst_mgr);
>  	enum transcoder trans = pipe_config->cpu_transcoder;
> +	bool first_mst_stream = intel_dp->active_mst_links == 1;
>  
>  	drm_WARN_ON(&dev_priv->drm, pipe_config->has_pch_encoder);
>  
> @@ -879,6 +880,9 @@ static void intel_mst_enable_dp(struct intel_atomic_state *state,
>  
>  	wait_for_act_sent(encoder, pipe_config);
>  
> +	if (first_mst_stream)
> +		intel_ddi_wait_for_fec_status(encoder, pipe_config, true);
> +
>  	drm_dp_add_payload_part2(&intel_dp->mst_mgr, &state->base,
>  				 drm_atomic_get_mst_payload_state(mst_state, connector->port));
>  
> -- 
> 2.39.2
>