Re: [PATCH] drm/radeon/dp: check for errors in dpcd reads

["Christian König" <deathsimple@vodafone.de>]

Am 30.04.2014 15:27, schrieb Alex Deucher:
> Check to make sure the transaction succeeded before
> using the register value.  Fixes occasional link training
> problems.
>
> Noticed-by: Sergei Antonov <saproj@gmail.com>
> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Applied to my 3.15 queue.

Christian.

> ---
>   drivers/gpu/drm/radeon/atombios_dp.c | 44 ++++++++++++++++++++----------------
>   1 file changed, 25 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/gpu/drm/radeon/atombios_dp.c b/drivers/gpu/drm/radeon/atombios_dp.c
> index bc0119f..54e4f52 100644
> --- a/drivers/gpu/drm/radeon/atombios_dp.c
> +++ b/drivers/gpu/drm/radeon/atombios_dp.c
> @@ -366,11 +366,11 @@ static void radeon_dp_probe_oui(struct radeon_connector *radeon_connector)
>   	if (!(dig_connector->dpcd[DP_DOWN_STREAM_PORT_COUNT] & DP_OUI_SUPPORT))
>   		return;
>   
> -	if (drm_dp_dpcd_read(&radeon_connector->ddc_bus->aux, DP_SINK_OUI, buf, 3))
> +	if (drm_dp_dpcd_read(&radeon_connector->ddc_bus->aux, DP_SINK_OUI, buf, 3) == 3)
>   		DRM_DEBUG_KMS("Sink OUI: %02hx%02hx%02hx\n",
>   			      buf[0], buf[1], buf[2]);
>   
> -	if (drm_dp_dpcd_read(&radeon_connector->ddc_bus->aux, DP_BRANCH_OUI, buf, 3))
> +	if (drm_dp_dpcd_read(&radeon_connector->ddc_bus->aux, DP_BRANCH_OUI, buf, 3) == 3)
>   		DRM_DEBUG_KMS("Branch OUI: %02hx%02hx%02hx\n",
>   			      buf[0], buf[1], buf[2]);
>   }
> @@ -419,21 +419,23 @@ int radeon_dp_get_panel_mode(struct drm_encoder *encoder,
>   
>   	if (dp_bridge != ENCODER_OBJECT_ID_NONE) {
>   		/* DP bridge chips */
> -		drm_dp_dpcd_readb(&radeon_connector->ddc_bus->aux,
> -				  DP_EDP_CONFIGURATION_CAP, &tmp);
> -		if (tmp & 1)
> -			panel_mode = DP_PANEL_MODE_INTERNAL_DP2_MODE;
> -		else if ((dp_bridge == ENCODER_OBJECT_ID_NUTMEG) ||
> -			 (dp_bridge == ENCODER_OBJECT_ID_TRAVIS))
> -			panel_mode = DP_PANEL_MODE_INTERNAL_DP1_MODE;
> -		else
> -			panel_mode = DP_PANEL_MODE_EXTERNAL_DP_MODE;
> +		if (drm_dp_dpcd_readb(&radeon_connector->ddc_bus->aux,
> +				      DP_EDP_CONFIGURATION_CAP, &tmp) == 1) {
> +			if (tmp & 1)
> +				panel_mode = DP_PANEL_MODE_INTERNAL_DP2_MODE;
> +			else if ((dp_bridge == ENCODER_OBJECT_ID_NUTMEG) ||
> +				 (dp_bridge == ENCODER_OBJECT_ID_TRAVIS))
> +				panel_mode = DP_PANEL_MODE_INTERNAL_DP1_MODE;
> +			else
> +				panel_mode = DP_PANEL_MODE_EXTERNAL_DP_MODE;
> +		}
>   	} else if (connector->connector_type == DRM_MODE_CONNECTOR_eDP) {
>   		/* eDP */
> -		drm_dp_dpcd_readb(&radeon_connector->ddc_bus->aux,
> -				  DP_EDP_CONFIGURATION_CAP, &tmp);
> -		if (tmp & 1)
> -			panel_mode = DP_PANEL_MODE_INTERNAL_DP2_MODE;
> +		if (drm_dp_dpcd_readb(&radeon_connector->ddc_bus->aux,
> +				      DP_EDP_CONFIGURATION_CAP, &tmp) == 1) {
> +			if (tmp & 1)
> +				panel_mode = DP_PANEL_MODE_INTERNAL_DP2_MODE;
> +		}
>   	}
>   
>   	return panel_mode;
> @@ -809,11 +811,15 @@ void radeon_dp_link_train(struct drm_encoder *encoder,
>   	else
>   		dp_info.enc_id |= ATOM_DP_CONFIG_LINK_A;
>   
> -	drm_dp_dpcd_readb(&radeon_connector->ddc_bus->aux, DP_MAX_LANE_COUNT, &tmp);
> -	if (ASIC_IS_DCE5(rdev) && (tmp & DP_TPS3_SUPPORTED))
> -		dp_info.tp3_supported = true;
> -	else
> +	if (drm_dp_dpcd_readb(&radeon_connector->ddc_bus->aux, DP_MAX_LANE_COUNT, &tmp)
> +	    == 1) {
> +		if (ASIC_IS_DCE5(rdev) && (tmp & DP_TPS3_SUPPORTED))
> +			dp_info.tp3_supported = true;
> +		else
> +			dp_info.tp3_supported = false;
> +	} else {
>   		dp_info.tp3_supported = false;
> +	}
>   
>   	memcpy(dp_info.dpcd, dig_connector->dpcd, DP_RECEIVER_CAP_SIZE);
>   	dp_info.rdev = rdev;