Re: [RFC PATCH v2 3/5] drm/msm/dp: support finding next bridge even for DP interfaces

[Abhinav Kumar <quic_abhinavk@quicinc.com>]

On 2/11/2022 2:40 PM, Dmitry Baryshkov wrote:
> It is possible to supply display-connector (bridge) to the DP interface,
> add support for parsing it too.
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> ---
>   drivers/gpu/drm/msm/dp/dp_parser.c | 19 ++++++++++++-------
>   1 file changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_parser.c b/drivers/gpu/drm/msm/dp/dp_parser.c
> index 901d7967370f..1056b8d5755b 100644
> --- a/drivers/gpu/drm/msm/dp/dp_parser.c
> +++ b/drivers/gpu/drm/msm/dp/dp_parser.c
> @@ -301,17 +301,22 @@ static int dp_parser_parse(struct dp_parser *parser, int connector_type)
>   		return rc;
>   
>   	/*
> -	 * Currently we support external bridges only for eDP connectors.
> +	 * External bridges are mandatory for eDP interfaces: one has to
> +	 * provide at least an eDP panel (which gets wrapped into panel-bridge).
>   	 *
> -	 * No external bridges are expected for the DisplayPort connector,
> -	 * it is physically present in a form of a DP or USB-C connector.
> +	 * For DisplayPort interfaces external bridges are optional, so
> +	 * silently ignore an error if one is not present (-ENODEV).
>   	 */
> -	if (connector_type == DRM_MODE_CONNECTOR_eDP) {
> -		rc = dp_parser_find_next_bridge(parser);
> -		if (rc) {
> -			DRM_ERROR("DP: failed to find next bridge\n");
> +	rc = dp_parser_find_next_bridge(parser);
> +	if (rc == -ENODEV) {
> +		if (connector_type == DRM_MODE_CONNECTOR_eDP) {
> +			DRM_ERROR("eDP: next bridge is not present\n");
>   			return rc;
>   		}
> +	} else if (rc) {
> +		if (rc != -EPROBE_DEFER)
> +			DRM_ERROR("DP: error parsing next bridge: %d\n", rc);
> +		return rc;
>   	}

How is this silently ignoring?

static int dp_display_bind(struct device *dev, struct device *master,
                void *data)
{
     int rc = 0;
     struct dp_display_private *dp = dev_get_dp_display_private(dev);
     struct msm_drm_private *priv = dev_get_drvdata(master);
     struct drm_device *drm = priv->dev;

     dp->dp_display.drm_dev = drm;
     priv->dp[dp->id] = &dp->dp_display;

     rc = dp->parser->parse(dp->parser, dp->dp_display.connector_type);
     if (rc) {
         DRM_ERROR("device tree parsing failed\n");
         goto end;
     }

dp_display_bind will still fail if a bridge is not found.

If supplying a bridge is optional even this should succeed right?

>   
>   	/* Map the corresponding regulator information according to