linux-kernel - Re: [PATCH 10/11] drm/bridge: anx7625: update bridge

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Message-ID: <ne35ljkudi5jta2cby7fgjzqsd5sjpwcjpwhv6kmedq6nomho5@txynsflvtc6f>
Date: Tue, 25 Feb 2025 19:58:24 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Ayushi Makhija <quic_amakhija@...cinc.com>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	freedreno@...ts.freedesktop.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	robdclark@...il.com, sean@...rly.run, marijn.suijten@...ainline.org, 
	andersson@...nel.org, robh@...nel.org, robh+dt@...nel.org, krzk+dt@...nel.org, 
	konradybcio@...nel.org, conor+dt@...nel.org, andrzej.hajda@...el.com, 
	neil.armstrong@...aro.org, rfoss@...nel.org, Laurent.pinchart@...asonboard.com, 
	jonas@...boo.se, jernej.skrabec@...il.com, quic_abhinavk@...cinc.com, 
	quic_rajeevny@...cinc.com, quic_vproddut@...cinc.com, quic_jesszhan@...cinc.com
Subject: Re: [PATCH 10/11] drm/bridge: anx7625: update bridge_ops and sink
 detect logic

On Tue, Feb 25, 2025 at 05:48:23PM +0530, Ayushi Makhija wrote:
> The anx7625_link_bridge() checks if a device is a not a panel
> bridge and add DRM_BRIDGE_OP_HPD and DRM_BRIDGE_OP_DETECT to
> the bridge operations. However, on port 1 of the anx7625
> bridge, any device added is always treated as a panel
> bridge, preventing connector_detect function from being
> called. To resolve this, instead of just checking if it is a
> panel bridge, we should verify the type of panel bridge
> whether it is a DisplayPort or eDP panel. If the panel
> bridge is of the DisplayPort type, we should add
> DRM_BRIDGE_OP_HPD or DRM_BRIDGE_OP_DETECT to the bridge
> operations.
> 
> In the anx7625_sink_detect(), the device is checked to see
> if it is a panel bridge, and it always sends a "connected"
> status to the connector. When adding the DP port on port 1 of the
> anx7625, it incorrectly treats it as a panel bridge and sends an
> always "connected" status. Instead of checking the status on the
> panel bridge, it's better to check the hpd_status for connectors
> like DisplayPort. This way, it verifies the hpd_status variable
> before sending the status to the connector.
> 
> Signed-off-by: Ayushi Makhija <quic_amakhija@...cinc.com>
> ---
>  drivers/gpu/drm/bridge/analogix/anx7625.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/analogix/anx7625.c b/drivers/gpu/drm/bridge/analogix/anx7625.c
> index d2655bf46842..9b6303267924 100644
> --- a/drivers/gpu/drm/bridge/analogix/anx7625.c
> +++ b/drivers/gpu/drm/bridge/analogix/anx7625.c
> @@ -1814,9 +1814,6 @@ static enum drm_connector_status anx7625_sink_detect(struct anx7625_data *ctx)
>  
>  	DRM_DEV_DEBUG_DRIVER(dev, "sink detect\n");
>  
> -	if (ctx->pdata.panel_bridge)
> -		return connector_status_connected;
> -
>  	return ctx->hpd_status ? connector_status_connected :
>  				     connector_status_disconnected;
>  }
> @@ -2596,9 +2593,10 @@ static int anx7625_link_bridge(struct drm_dp_aux *aux)
>  	platform->bridge.of_node = dev->of_node;
>  	if (!anx7625_of_panel_on_aux_bus(dev))
>  		platform->bridge.ops |= DRM_BRIDGE_OP_EDID;
> -	if (!platform->pdata.panel_bridge)
> -		platform->bridge.ops |= DRM_BRIDGE_OP_HPD |
> -					DRM_BRIDGE_OP_DETECT;
> +	if (!platform->pdata.panel_bridge ||
> +	    platform->pdata.panel_bridge->type == DRM_MODE_CONNECTOR_DisplayPort) {

This is incorrect, because there can be other kinds of bridges in the DP
chain. I think it's better to check for !eDP instead.

> +		platform->bridge.ops |= DRM_BRIDGE_OP_HPD | DRM_BRIDGE_OP_DETECT;
> +	}
>  	platform->bridge.type = platform->pdata.panel_bridge ?
>  				    DRM_MODE_CONNECTOR_eDP :
>  				    DRM_MODE_CONNECTOR_DisplayPort;
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry