[PATCH] drm/tegra: rgb: Fix the unbound reference count

[Thierry Reding]

On Wed, May 07, 2025 at 04:10:07PM +0000, Biju Das wrote:
> Hi Thierry,
> 
> > -----Original Message-----
> > From: Thierry Reding <thierry.reding at gmail.com>
> > Sent: 07 May 2025 17:00
> > To: Biju Das <biju.das.jz at bp.renesas.com>
> > Subject: Re: [PATCH] drm/tegra: rgb: Fix the unbound reference count
> > 
> > On Wed, Feb 05, 2025 at 11:21:35AM +0000, Biju Das wrote:
> > > The of_get_child_by_name() increments the refcount in
> > > tegra_dc_rgb_probe, but the driver does not decrement the refcount
> > > during unbind. Fix the unbound reference count using devm_add_action_or_reset() helper.
> > >
> > > Fixes: d8f4a9eda006 ("drm: Add NVIDIA Tegra20 support")
> > > Signed-off-by: Biju Das <biju.das.jz at bp.renesas.com>
> > > ---
> > >  drivers/gpu/drm/tegra/rgb.c | 14 +++++++++++++-
> > >  1 file changed, 13 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/tegra/rgb.c b/drivers/gpu/drm/tegra/rgb.c
> > > index 1e8ec50b759e..2065157daab3 100644
> > > --- a/drivers/gpu/drm/tegra/rgb.c
> > > +++ b/drivers/gpu/drm/tegra/rgb.c
> > > @@ -200,6 +200,11 @@ static const struct drm_encoder_helper_funcs tegra_rgb_encoder_helper_funcs = {
> > >  	.atomic_check = tegra_rgb_encoder_atomic_check,  };
> > >
> > > +static void tegra_dc_of_node_put(void *data) {
> > > +	of_node_put(data);
> > > +}
> > > +
> > >  int tegra_dc_rgb_probe(struct tegra_dc *dc)  {
> > >  	struct device_node *np;
> > > @@ -207,7 +212,14 @@ int tegra_dc_rgb_probe(struct tegra_dc *dc)
> > >  	int err;
> > >
> > >  	np = of_get_child_by_name(dc->dev->of_node, "rgb");
> > > -	if (!np || !of_device_is_available(np))
> > > +	if (!np)
> > > +		return -ENODEV;
> > > +
> > > +	err = devm_add_action_or_reset(dc->dev, tegra_dc_of_node_put,
> > > +dc->dev);
> > 
> > Actually, I think this needs to be:
> > 
> >   err = devm_add_action_or_reset(dc->dev, tegra_dc_of_node_put, np);
> > 
> > otherwise tegra_dc_of_node_put() would attempt to call of_node_put() on
> > dc->dev, which won't work, or rather cause corruption of some sort.
> > 
> > Shout if you disagree.
> 
> I agree, is it something you can do while applying or you want me to send v2?
> Please let me know.

It's already done, thanks for confirming and for the patch.

Thierry
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <https://lists.freedesktop.org/archives/dri-devel/attachments/20250508/3398ac08/attachment.sig>