linux-kernel - Re: imx8m-blk-ctrl: WARNING, no release() function

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Message-ID: <20241216235456.3a6b07a2@booty>
Date: Mon, 16 Dec 2024 23:54:56 +0100
From: Luca Ceresoli <luca.ceresoli@...tlin.com>
To: Francesco Dolcini <francesco@...cini.it>
Cc: linux-pm@...r.kernel.org, imx@...ts.linux.dev, Ulf Hansson
 <ulf.hansson@...aro.org>, Shawn Guo <shawnguo@...nel.org>, Sascha Hauer
 <s.hauer@...gutronix.de>, Pengutronix Kernel Team <kernel@...gutronix.de>,
 Fabio Estevam <festevam@...il.com>, Peng Fan <peng.fan@....com>, Marek
 Vasut <marex@...x.de>, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, Lucas Stach <l.stach@...gutronix.de>, Jindong
 Yue <jindong.yue@....com>, Benjamin Gaignard
 <benjamin.gaignard@...labora.com>, Paul Elder
 <paul.elder@...asonboard.com>, Hervé Codina
 <herve.codina@...tlin.com>
Subject: Re: imx8m-blk-ctrl: WARNING, no release() function

Hi Francesco,

+Cc: Jindong, Benjamin, Paul (recent committers, in lack of an
imx8m-blk-ctrl.c maintainer)
+Cc: Hervé (stumbled on this issue too)

On Thu, 12 Dec 2024 15:10:03 +0100
Francesco Dolcini <francesco@...cini.it> wrote:

> Hello,
> on v6.13-rc2 (PREEMPT_RT, if it matters), I have the following warning
> 
> [    4.615793] ------------[ cut here ]------------
> [    4.615814] Device 'mediablk-mipi-csi2-1' does not have a release() function, it is broken and must be fixed. See Documentation/core-api/kobject.rst.

Thanks for the report. It is happening also here after upgrading from
6.13-rc1 to 6.13-rc3.

This originates from drivers/pmdomain/imx/imx8m-blk-ctrl.c

I bisected and the initial commit exposing this warning is:

  commit b8f7bbd1f4ecff6d6277b8c454f62bb0a1c6dbe4
  Author: Ulf Hansson <ulf.hansson@...aro.org>
  Date:   Fri Nov 22 14:42:02 2024 +0100

    pmdomain: core: Add missing put_device()
    
    When removing a genpd we don't clean up the genpd->dev correctly. Let's add
    the missing put_device() in genpd_free_data() to fix this.
    
    Fixes: 401ea1572de9 ("PM / Domain: Add struct device to genpd")
    Cc: stable@...r.kernel.org
    Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
    Message-ID: <20241122134207.157283-2-ulf.hansson@...aro.org>

Superficially, it looks to me like a legitimate commit which exposes a
pre-existing flaw in drivers/pmdomain/imx/imx8m-blk-ctrl.c.

I have no more info at the moment.

Luca

-- 
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com