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

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Message-ID: <20251021151435.23a03b85@kmaincent-XPS-13-7390>
Date: Tue, 21 Oct 2025 15:14:35 +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

On Tue, 14 Oct 2025 18:21:22 +0200
Kory Maincent <kory.maincent@...tlin.com> wrote:

> 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.

Maxime is it okay to merge this to the right drm fix branch as I am currently
working on the tilcdc cleaning process that will land into drm misc next.

Also I intend to remove the tilcdc panel subdriver and its binding as it
can be replaced by the simple panel driver. I know it is unusual to remove a
binding but the driver and the binding are crappy and legacy. What do you think?

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