linux-kernel - Re: [PATCH v2] drm/bridge: Fix assignment of the of

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Message-ID: <CAA8EJpopyzeVXMzZAiakEmJ9S=29FKt43AHypSYyOuo_NbSJbw@mail.gmail.com>
Date: Thu, 31 Oct 2024 17:48:24 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Johan Hovold <johan@...nel.org>
Cc: Abel Vesa <abel.vesa@...aro.org>, Andrzej Hajda <andrzej.hajda@...el.com>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>, Jonas Karlman <jonas@...boo.se>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
	stable@...r.kernel.org
Subject: Re: [PATCH v2] drm/bridge: Fix assignment of the of_node of the
 parent to aux bridge

On Mon, 21 Oct 2024 at 10:23, Johan Hovold <johan@...nel.org> wrote:
>
> On Fri, Oct 18, 2024 at 03:49:34PM +0300, Abel Vesa wrote:
> > The assignment of the of_node to the aux bridge needs to mark the
> > of_node as reused as well, otherwise resource providers like pinctrl will
> > report a gpio as already requested by a different device when both pinconf
> > and gpios property are present.
>
> I don't think you need a gpio property for that to happen, right? And
> this causes probe to fail IIRC?

No, just having a pinctrl property in the bridge device is enough.
Without this fix when the aux subdevice is being bound to the driver,
the pinctrl_bind_pins() will attempt to bind pins, which are already
in use by the actual bridge device.

>
> > Fix that by using the device_set_of_node_from_dev() helper instead.
> >
> > Fixes: 6914968a0b52 ("drm/bridge: properly refcount DT nodes in aux bridge drivers")
>
> This is not the commit that introduced the issue.
>
> > Cc: stable@...r.kernel.org      # 6.8
>
> I assume there are no existing devicetrees that need this since then we
> would have heard about it sooner. Do we still need to backport it?
>
> When exactly are you hitting this?
>
> > Cc: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> > Signed-off-by: Abel Vesa <abel.vesa@...aro.org>
> > ---
> > Changes in v2:
> > - Re-worded commit to be more explicit of what it fixes, as Johan suggested
> > - Used device_set_of_node_from_dev() helper, as per Johan's suggestion
> > - Added Fixes tag and cc'ed stable
> > - Link to v1: https://lore.kernel.org/r/20241017-drm-aux-bridge-mark-of-node-reused-v1-1-7cd5702bb4f2@linaro.org
>
> Patch itself looks good now.
>
> Johan



-- 
With best wishes
Dmitry