Re: [RFC PATCH v2 1/5] drm/msm/dp: fix panel bridge attachment

[Kuogee Hsieh <quic_khsieh@quicinc.com>]

On 2/11/2022 2:40 PM, Dmitry Baryshkov wrote:
> In commit 8a3b4c17f863 ("drm/msm/dp: employ bridge mechanism for display
> enable and disable") the DP driver received a drm_bridge instance, which
> is always attached to the encoder as a root bridge. However it conflicts
> with the panel_bridge support for eDP panels. The panel bridge attaches
> to the encoder before the "dp" bridge has a chace to do so. Change
> panel_bridge attachment to come after dp_bridge attachment.
>
> Fixes: 8a3b4c17f863 ("drm/msm/dp: employ bridge mechanism for display enable and disable")
> Cc: Kuogee Hsieh <quic_khsieh@quicinc.com>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Tested-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
> ---
>   drivers/gpu/drm/msm/dp/dp_drm.c | 21 +++++++++++----------
>   1 file changed, 11 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_drm.c b/drivers/gpu/drm/msm/dp/dp_drm.c
> index d4d360d19eba..26ef41a4c1b6 100644
> --- a/drivers/gpu/drm/msm/dp/dp_drm.c
> +++ b/drivers/gpu/drm/msm/dp/dp_drm.c
> @@ -169,16 +169,6 @@ struct drm_connector *dp_drm_connector_init(struct msm_dp *dp_display)
>   
>   	drm_connector_attach_encoder(connector, dp_display->encoder);
>   
> -	if (dp_display->panel_bridge) {
> -		ret = drm_bridge_attach(dp_display->encoder,
> -					dp_display->panel_bridge, NULL,
> -					DRM_BRIDGE_ATTACH_NO_CONNECTOR);
> -		if (ret < 0) {
> -			DRM_ERROR("failed to attach panel bridge: %d\n", ret);
> -			return ERR_PTR(ret);
> -		}
> -	}
> -
>   	return connector;
>   }
>   
> @@ -246,5 +236,16 @@ struct drm_bridge *msm_dp_bridge_init(struct msm_dp *dp_display, struct drm_devi
>   		return ERR_PTR(rc);
>   	}
>   
> +	if (dp_display->panel_bridge) {
> +		rc = drm_bridge_attach(dp_display->encoder,
> +					dp_display->panel_bridge, bridge,
> +					DRM_BRIDGE_ATTACH_NO_CONNECTOR);
> +		if (rc < 0) {
> +			DRM_ERROR("failed to attach panel bridge: %d\n", rc);
> +			drm_bridge_remove(bridge);
> +			return ERR_PTR(rc);
> +		}
> +	}
> +
>   	return bridge;
>   }