[RFC 06/13] drm/i915: Check for FRL training before DP Link training

[Shankar, Uma]

> -----Original Message-----
> From: Nautiyal, Ankit K <ankit.k.nautiyal at intel.com>
> Sent: Thursday, October 15, 2020 4:23 PM
> To: intel-gfx at lists.freedesktop.org
> Cc: dri-devel at lists.freedesktop.org; Shankar, Uma <uma.shankar at intel.com>;
> Kulkarni, Vandita <vandita.kulkarni at intel.com>; ville.syrjala at linux.intel.com;
> Sharma, Swati2 <swati2.sharma at intel.com>
> Subject: [RFC 06/13] drm/i915: Check for FRL training before DP Link training
> 
> This patch calls functions to check FRL training requirements for an HDMI2.1 sink,
> when connected through PCON.
> The call is made before the DP link training. In case FRL is not required or failure
> during FRL training, the TMDS mode is selected for the pcon.
> 
> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_ddi.c | 2 ++
> drivers/gpu/drm/i915/display/intel_dp.c  | 2 ++
>  2 files changed, 4 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c
> b/drivers/gpu/drm/i915/display/intel_ddi.c
> index bb0b9930958f..1834e5de60a7 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -3484,6 +3484,8 @@ static void tgl_ddi_pre_enable_dp(struct
> intel_atomic_state *state,
>  	if (!is_mst)
>  		intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
> 
> +	intel_dp_check_frl_training(intel_dp);

Good to move it near start_link_training to stay consistent with rest of the calls.

> +
>  	intel_dp_sink_set_decompression_state(intel_dp, crtc_state, true);
>  	/*
>  	 * DDI FEC: "anticipates enabling FEC encoding sets the FEC_READY bit
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> b/drivers/gpu/drm/i915/display/intel_dp.c
> index c1342b5e7781..668165dd2b1a 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -4206,6 +4206,7 @@ static void intel_enable_dp(struct intel_atomic_state
> *state,
> 
>  	intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
>  	intel_dp_configure_protocol_converter(intel_dp);
> +	intel_dp_check_frl_training(intel_dp);
>  	intel_dp_start_link_train(intel_dp, pipe_config);
>  	intel_dp_stop_link_train(intel_dp, pipe_config);
> 
> @@ -6127,6 +6128,7 @@ int intel_dp_retrain_link(struct intel_encoder
> *encoder,
>  		    !intel_dp_mst_is_master_trans(crtc_state))
>  			continue;
> 
> +		intel_dp_check_frl_training(intel_dp);
>  		intel_dp_start_link_train(intel_dp, crtc_state);
>  		intel_dp_stop_link_train(intel_dp, crtc_state);
>  		break;
> --
> 2.17.1