linux-kernel - Re: [PATCH] drm/omap: dsi: Fix deferred probe warnings

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Date:   Wed, 12 Apr 2023 11:50:44 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Tomi Valkeinen <tomba@...nel.org>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Sebastian Reichel <sre@...nel.org>,
        dri-devel@...ts.freedesktop.org, linux-omap@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/omap: dsi: Fix deferred probe warnings

Hi Tony,

Thank you for the patch.

On Wed, Apr 12, 2023 at 10:39:53AM +0300, Tony Lindgren wrote:
> We may not have dsi->dsidev initialized during probe, and that can
> lead into various dsi related warnings as omap_dsi_host_detach() gets
> called with dsi->dsidev set to NULL.
> 
> The warnings can be "Fixed dependency cycle(s)" followed by a
> WARNING: CPU: 0 PID: 787 at drivers/gpu/drm/omapdrm/dss/dsi.c:4414.

How can this happen ? I assume .detach() can't be called without a
priori successful call to .attach(), that that sets dsi->dsidev.

> Let's fix the warnings by checking for a valid dsi->dsidev.
> 
> Signed-off-by: Tony Lindgren <tony@...mide.com>
> ---
>  drivers/gpu/drm/omapdrm/dss/dsi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/omapdrm/dss/dsi.c b/drivers/gpu/drm/omapdrm/dss/dsi.c
> --- a/drivers/gpu/drm/omapdrm/dss/dsi.c
> +++ b/drivers/gpu/drm/omapdrm/dss/dsi.c
> @@ -4411,7 +4411,7 @@ static int omap_dsi_host_detach(struct mipi_dsi_host *host,
>  {
>  	struct dsi_data *dsi = host_to_omap(host);
>  
> -	if (WARN_ON(dsi->dsidev != client))
> +	if (dsi->dsidev && WARN_ON(dsi->dsidev != client))
>  		return -EINVAL;
>  
>  	cancel_delayed_work_sync(&dsi->dsi_disable_work);

-- 
Regards,

Laurent Pinchart