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

[Tomi Valkeinen]

On 12/04/2023 11:50, Laurent Pinchart wrote:
> 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.

I had a quick look, and the driver calls mipi_dsi_host_register() in 
probe, and mipi_dsi_host_unregister() in remove.

mipi_dsi_host_unregister() always calls mipi_dsi_detach(), but I don't 
think mipi_dsi_host_register() always calls attach, which happens later 
when the peripheral probes.

 Tomi

> > Let's fix the warnings by checking for a valid dsi->dsidev.
> >
> > Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx>
> > ---
> >   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);