linux-kernel - Re: [PATCH] clk: scu/imx8qxp: do not register driver in probe()

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Message-ID: <10809444.nUPlyArG6x@steina-w>
Date: Wed, 11 Feb 2026 15:43:34 +0100
From: Alexander Stein <alexander.stein@...tq-group.com>
To: abelvesa@...nel.org, peng.fan@....com, mturquette@...libre.com,
 sboyd@...nel.org, Frank.Li@....com, s.hauer@...gutronix.de,
 kernel@...gutronix.de, festevam@...il.com, gregkh@...uxfoundation.org,
 rafael@...nel.org, hanguidong02@...il.com, Danilo Krummrich <dakr@...nel.org>
Cc: driver-core@...ts.linux.dev, linux-kernel@...r.kernel.org,
 linux-clk@...r.kernel.org, imx@...ts.linux.dev,
 linux-arm-kernel@...ts.infradead.org, Danilo Krummrich <dakr@...nel.org>
Subject: Re: [PATCH] clk: scu/imx8qxp: do not register driver in probe()

Hi Danilo,

Am Mittwoch, 11. Februar 2026, 15:23:16 CET schrieb Danilo Krummrich:
> imx_clk_scu_init() registers the imx_clk_scu_driver while commonly being
> called from IMX driver's probe() callbacks.
> 
> However, it neither makes sense to register drivers from probe()
> callbacks of other drivers, nor does the driver core allow registering
> drivers with a device lock already being held.
> 
> The latter was revealed by commit dc23806a7c47 ("driver core: enforce
> device_lock for driver_match_device()") leading to a deadlock condition
> described in [1].
> 
> Additionally, nothing seems to unregister the imx_clk_scu_driver once
> the corresponding driver module is unloaded, which leaves the
> driver-core with a dangling pointer.
> 
> Hence, register the imx_clk_scu_driver from module_init() and unregister
> it in module_exit().
> 
> Fixes: dc23806a7c47 ("driver core: enforce device_lock for driver_match_device()")
> Fixes: 220175cd3979 ("clk: imx: scu: fix build break when compiled as modules")
> Reported-by: Alexander Stein <alexander.stein@...tq-group.com>
> Closes: https://lore.kernel.org/lkml/13955113.uLZWGnKmhe@steina-w/
> Link: https://lore.kernel.org/lkml/DFU7CEPUSG9A.1KKGVW4HIPMSH@kernel.org/ [1]
> Signed-off-by: Danilo Krummrich <dakr@...nel.org>

Thanks for the patch.
Tested-by: Alexander Stein <alexander.stein@...tq-group.com> # TQMa8x/MBa8x

> ---
> I plan to send the driver-core PR for 7.0-rc1 soon, which will also contain
> commit dc23806a7c47 ("driver core: enforce device_lock for
> driver_match_device()").
> 
> It also contains an IOMMU commit similar to this one:
> https://patch.msgid.link/20260121141215.29658-1-dakr@kernel.org
> 
> The commit was originally scheduled for 6.19-rc7, but was deferred to 7.0-rc1 in
> case more of those cases pop up (which now happened).
> ---
>  drivers/clk/imx/clk-imx8qxp.c | 24 +++++++++++++++++++++++-
>  drivers/clk/imx/clk-scu.c     | 12 +++++++++++-
>  drivers/clk/imx/clk-scu.h     |  2 ++
>  3 files changed, 36 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clk/imx/clk-imx8qxp.c b/drivers/clk/imx/clk-imx8qxp.c
> index 3ae162625bb1..d89a2f40771e 100644
> --- a/drivers/clk/imx/clk-imx8qxp.c
> +++ b/drivers/clk/imx/clk-imx8qxp.c
> @@ -346,7 +346,29 @@ static struct platform_driver imx8qxp_clk_driver = {
>  	},
>  	.probe = imx8qxp_clk_probe,
>  };
> -module_platform_driver(imx8qxp_clk_driver);
> +
> +static int __init imx8qxp_init(void)
> +{
> +	int ret;
> +
> +	ret = platform_driver_register(&imx8qxp_clk_driver);
> +	if (ret)
> +		return ret;
> +
> +	ret = imx_clk_scu_module_init();
> +	if (ret)
> +		platform_driver_unregister(&imx8qxp_clk_driver);
> +
> +	return ret;
> +}
> +module_init(imx8qxp_init);
> +
> +static void __exit imx8qxp_exit(void)
> +{
> +	imx_clk_scu_module_exit();
> +	platform_driver_unregister(&imx8qxp_clk_driver);
> +}
> +module_exit(imx8qxp_exit);
>  
>  MODULE_AUTHOR("Aisheng Dong <aisheng.dong@....com>");
>  MODULE_DESCRIPTION("NXP i.MX8QXP clock driver");
> diff --git a/drivers/clk/imx/clk-scu.c b/drivers/clk/imx/clk-scu.c
> index 34c9dc1fb20e..c90d21e05f91 100644
> --- a/drivers/clk/imx/clk-scu.c
> +++ b/drivers/clk/imx/clk-scu.c
> @@ -191,6 +191,16 @@ static bool imx_scu_clk_is_valid(u32 rsrc_id)
>  	return p != NULL;
>  }
>  
> +int __init imx_clk_scu_module_init(void)
> +{
> +	return platform_driver_register(&imx_clk_scu_driver);
> +}
> +
> +void __exit imx_clk_scu_module_exit(void)
> +{
> +	return platform_driver_unregister(&imx_clk_scu_driver);
> +}
> +
>  int imx_clk_scu_init(struct device_node *np,
>  		     const struct imx_clk_scu_rsrc_table *data)
>  {
> @@ -215,7 +225,7 @@ int imx_clk_scu_init(struct device_node *np,
>  		rsrc_table = data;
>  	}
>  
> -	return platform_driver_register(&imx_clk_scu_driver);
> +	return 0;
>  }
>  
>  /*
> diff --git a/drivers/clk/imx/clk-scu.h b/drivers/clk/imx/clk-scu.h
> index af7b697f51ca..ca82f2cce897 100644
> --- a/drivers/clk/imx/clk-scu.h
> +++ b/drivers/clk/imx/clk-scu.h
> @@ -25,6 +25,8 @@ extern const struct imx_clk_scu_rsrc_table imx_clk_scu_rsrc_imx8dxl;
>  extern const struct imx_clk_scu_rsrc_table imx_clk_scu_rsrc_imx8qxp;
>  extern const struct imx_clk_scu_rsrc_table imx_clk_scu_rsrc_imx8qm;
>  
> +int __init imx_clk_scu_module_init(void);
> +void __exit imx_clk_scu_module_exit(void);
>  int imx_clk_scu_init(struct device_node *np,
>  		     const struct imx_clk_scu_rsrc_table *data);
>  struct clk_hw *imx_scu_of_clk_src_get(struct of_phandle_args *clkspec,
> 
> base-commit: 192c0159402e6bfbe13de6f8379546943297783d
> 


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