Re: [PATCH v4 4/9] drm/vc4: hdmi: Propagate -EDEADLK to the top level

["Maíra Canal" <mcanal@igalia.com>]

On 09/11/26 21:13, 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.
> 
> Acked-by: Maxime Ripard <mripard@kernel.org>
> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>

Reviewed-by: Maíra Canal <mcanal@igalia.com>

Best regards,
- Maíra

> ---
>   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 0e6696644687..fc9d5fe07849 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -343,12 +343,11 @@ 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
> @@ -367,17 +366,9 @@ 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,
> @@ -415,10 +406,10 @@ 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;
>   }
>   
>   static int vc4_hdmi_connector_get_modes(struct drm_connector *connector)
>