linux-kernel - Re: [PATCH] drm/tilcdc: Fix removal actions in case of failed probe

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Message-ID: <20251014182122.5f63b027@kmaincent-XPS-13-7390>
Date: Tue, 14 Oct 2025 18:21:22 +0200
From: Kory Maincent <kory.maincent@...tlin.com>
To: Maxime Ripard <mripard@...nel.org>
Cc: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>, Douglas Anderson
 <dianders@...omium.org>, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, Bajjuri Praneeth <praneeth@...com>, Louis
 Chauvet <louis.chauvet@...tlin.com>, thomas.petazzoni@...tlin.com, Jyri
 Sarha <jyri.sarha@....fi>, Maarten Lankhorst
 <maarten.lankhorst@...ux.intel.com>, Thomas Zimmermann
 <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Simona Vetter
 <simona@...ll.ch>
Subject: Re: [PATCH] drm/tilcdc: Fix removal actions in case of failed probe

Hello Maxime,

On Tue, 14 Oct 2025 17:36:47 +0200
Maxime Ripard <mripard@...nel.org> wrote:

> On Tue, Oct 14, 2025 at 04:32:28PM +0200, Kory Maincent wrote:
> > From: "Kory Maincent (TI.com)" <kory.maincent@...tlin.com>
> > 
> > The drm_kms_helper_poll_fini() and drm_atomic_helper_shutdown() helpers
> > should only be called when the device has been successfully registered.
> > Currently, these functions are called unconditionally in tilcdc_fini(),
> > which causes warnings during probe deferral scenarios.
> > 
> > [    7.972317] WARNING: CPU: 0 PID: 23 at
> > drivers/gpu/drm/drm_atomic_state_helper.c:175
> > drm_atomic_helper_crtc_duplicate_state+0x60/0x68 ... [    8.005820]
> > drm_atomic_helper_crtc_duplicate_state from
> > drm_atomic_get_crtc_state+0x68/0x108 [    8.005858]
> > drm_atomic_get_crtc_state from drm_atomic_helper_disable_all+0x90/0x1c8 [
> >  8.005885]  drm_atomic_helper_disable_all from
> > drm_atomic_helper_shutdown+0x90/0x144 [    8.005911]
> > drm_atomic_helper_shutdown from tilcdc_fini+0x68/0xf8 [tilcdc] [
> > 8.005957]  tilcdc_fini [tilcdc] from tilcdc_pdev_probe+0xb0/0x6d4 [tilcdc]
> > 
> > Fix this by moving both drm_kms_helper_poll_fini() and
> > drm_atomic_helper_shutdown() inside the priv->is_registered conditional
> > block, ensuring they only execute after successful device registration.
> > 
> > Fixes: 3c4babae3c4a ("drm: Call drm_atomic_helper_shutdown() at
> > shutdown/remove time for misc drivers") Signed-off-by: Kory Maincent
> > (TI.com) <kory.maincent@...tlin.com> ---
> >  drivers/gpu/drm/tilcdc/tilcdc_drv.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/tilcdc/tilcdc_drv.c
> > b/drivers/gpu/drm/tilcdc/tilcdc_drv.c index 7caec4d38ddf..2031267a3490
> > 100644 --- a/drivers/gpu/drm/tilcdc/tilcdc_drv.c
> > +++ b/drivers/gpu/drm/tilcdc/tilcdc_drv.c
> > @@ -172,11 +172,11 @@ static void tilcdc_fini(struct drm_device *dev)
> >  	if (priv->crtc)
> >  		tilcdc_crtc_shutdown(priv->crtc);
> >  
> > -	if (priv->is_registered)
> > +	if (priv->is_registered) {
> >  		drm_dev_unregister(dev);
> > -
> > -	drm_kms_helper_poll_fini(dev);
> > -	drm_atomic_helper_shutdown(dev);
> > +		drm_kms_helper_poll_fini(dev);
> > +		drm_atomic_helper_shutdown(dev);
> > +	}
> >  	tilcdc_irq_uninstall(dev);
> >  	drm_mode_config_cleanup(dev);  
> 
> I don't think that's the right fix. tilcdc_fini is pretty complex
> because it gets called from multiple locations with various level of
> initialisation.
> 
> This is done because tilcdc_init is using a bunch of deprecated
> functions with better alternatives now, and those would make the job of
> tilcdc_fini much easier.
> 
> That's what we should be focusing on.

I am also currently focusing on improving this driver (which has indeed some
weird code leftover), but this work will land in drm misc next while this is a
fix for the current implementation which fix an unwanted warning.

Regards,
-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com