Re: [PATCH v10 43/69] drm/vc4: hdmi: Propagate -EDEADLK to the top level

On Fri, Jul 31, 2026 at 07:19:50PM +0300, Cristian Ciocaltea wrote:
> drm_connector_helper_funcs.detect_ctx() is expected to propagate
> -EDEADLK so that context owners, e.g. drm_helper_probe_detect_ctx(), can
> perform the required backoff and retry.
> 
> vc4_hdmi_handle_hotplug() instead runs its own retry loop and calls
> drm_modeset_backoff() on an acquire context it does not own.  This drops
> all locks in the context, including connection_mutex held by the core.
> 
> Drop the local retry logic and propagate -EDEADLK to the caller instead.
> This aligns VC4 with the expected detect_ctx() semantics.
> 
> Signed-off-by: Cristian Ciocaltea <[email protected]>
> ---
>  drivers/gpu/drm/vc4/vc4_hdmi.c | 23 +++++++----------------
>  1 file changed, 7 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> index ba16e7944cf3..72042fad04c5 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -344,12 +344,11 @@ static int vc4_hdmi_reset_link(struct drm_connector *connector,
>  	return drm_atomic_helper_reset_crtc(crtc, ctx);
>  }
>  
> -static void vc4_hdmi_handle_hotplug(struct vc4_hdmi *vc4_hdmi,
> -				    struct drm_modeset_acquire_ctx *ctx,
> -				    enum drm_connector_status status)
> +static int vc4_hdmi_handle_hotplug(struct vc4_hdmi *vc4_hdmi,
> +				   struct drm_modeset_acquire_ctx *ctx,
> +				   enum drm_connector_status status)
>  {
>  	struct drm_connector *connector = &vc4_hdmi->connector;
> -	int ret;
>  
>  	/*
>  	 * NOTE: This function should really be called with vc4_hdmi->mutex
> @@ -368,17 +367,9 @@ static void vc4_hdmi_handle_hotplug(struct vc4_hdmi *vc4_hdmi,
>  	drm_atomic_helper_connector_hdmi_hotplug(connector, ctx, status);
>  
>  	if (status != connector_status_connected)
> -		return;
> +		return 0;
>  
> -	for (;;) {
> -		ret = vc4_hdmi_reset_link(connector, ctx);
> -		if (ret == -EDEADLK) {
> -			drm_modeset_backoff(ctx);
> -			continue;
> -		}
> -
> -		break;
> -	}
> +	return vc4_hdmi_reset_link(connector, ctx);
>  }
>  
>  static int vc4_hdmi_connector_detect_ctx(struct drm_connector *connector,
> @@ -416,10 +407,10 @@ static int vc4_hdmi_connector_detect_ctx(struct drm_connector *connector,
>  			status = connector_status_connected;
>  	}
>  
> -	vc4_hdmi_handle_hotplug(vc4_hdmi, ctx, status);
> +	ret = vc4_hdmi_handle_hotplug(vc4_hdmi, ctx, status);
>  	pm_runtime_put(&vc4_hdmi->pdev->dev);
>  
> -	return status;
> +	return ret == -EDEADLK ? ret : status;

Don't we mask any error that isn't EDEADLK here?

Maxime

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