Re: [v6 2/4] drm/i915/fec: Set FEC_READY in FEC_CONFIGURATION

[Manasi Navare <manasi.d.navare@intel.com>]

On Mon, Nov 05, 2018 at 03:31:48PM -0800, Anusha Srivatsa wrote:
> If the panel supports FEC, the driver has to
> set the FEC_READY bit in the dpcd register:
> FEC_CONFIGURATION.
> 
> This has to happen before link training.
> 
> v2: s/intel_dp_set_fec_ready/intel_dp_sink_set_fec_ready
>    - change commit message. (Gaurav)
> 
> v3: rebased. (r-b Manasi)
> 
> v4: Use fec crtc state, before setting FEC_READY
> bit. (Anusha)
> 
> v5: Move to intel_ddi.c
> - Make the function static (Anusha)
> 
> Cc: dri-devel@lists.freedesktop.org
> Cc: Gaurav K Singh <gaurav.k.singh@intel.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Cc: Manasi Navare <manasi.d.navare@intel.com>
> Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_ddi.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index 46c1b9e12fbd..53a9b31e66a2 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -3051,6 +3051,20 @@ static void icl_program_mg_dp_mode(struct intel_digital_port *intel_dig_port)
>  	I915_WRITE(MG_DP_MODE(port, 1), ln1);
>  }
>  
> +static void intel_dp_sink_set_fec_ready(struct intel_dp *intel_dp,
> +					const struct intel_crtc_state *crtc_state,
> +					int state)

u8 state should be good enough since you are writing only a byte here

> +{
> +	int ret;
> +
> +	if (!crtc_state->fec_enable)
> +		return;
> +
> +	ret = drm_dp_dpcd_writeb(&intel_dp->aux, DP_FEC_CONFIGURATION, state);
> +	if (ret < 0)

This should ret <=0 since even if it writes 0 bytes its an error. Infact you dont need ret
you can just say"
if (drm_dp_dpcd_writeb(&intel_dp->aux, DP_FEC_CONFIGURATION, state) <= 0)

After the above changes,

Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>

Manasi
> +		DRM_DEBUG_KMS("Failed to get FEC enabled in sink\n");
> +}
> +
>  static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
>  				    const struct intel_crtc_state *crtc_state,
>  				    const struct drm_connector_state *conn_state)
> @@ -3091,6 +3105,7 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
>  		intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
>  	intel_dp_sink_set_decompression_state(intel_dp, crtc_state,
>  					      true);
> +	intel_dp_sink_set_fec_ready(intel_dp, crtc_state, DP_FEC_READY);
>  	intel_dp_start_link_train(intel_dp);
>  	if (port != PORT_A || INTEL_GEN(dev_priv) >= 9)
>  		intel_dp_stop_link_train(intel_dp);
> -- 
> 2.19.1
> 
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