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

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Message-ID: <20230913125036.GM5285@atomide.com>
Date:   Wed, 13 Sep 2023 15:50:36 +0300
From:   Tony Lindgren <tony@...mide.com>
To:     Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Sebastian Reichel <sre@...nel.org>,
        dri-devel@...ts.freedesktop.org, linux-omap@...r.kernel.org,
        linux-kernel@...r.kernel.org, Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...il.com>
Subject: Re: [PATCH] drm/omap: dsi: Fix deferred probe warnings

* Tomi Valkeinen <tomi.valkeinen@...asonboard.com> [230913 11:59]:
> On 12/04/2023 10:39, 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.
> > 
> > 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);
> 
> Shouldn't this rather be
> 
> if (!dsi->dsidev)
> 	return 0;
> 
> before the if (WARN_ON(dsi->dsidev != client)) line?
> 
> If dsi->dsidev is NULL, then attach hasn't been called, and we shouldn't do
> anything in the detach callback either.
> 
> With your change we'll end up doing all the work in the detach callback,
> without ever doing their counterpart in the attach side.

Oops, I'll check that thanks.

Tony