[PATCH v2] clk: scu/imx8qxp: do not register driver in probe()

[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].

Besides that, 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.

Also, if there are multiple matching devices for the imx8qxp_clk_driver,
imx8qxp_clk_probe() calls imx_clk_scu_init() multiple times.  However,
any subsequent call after the first one will fail, since the driver-core
does not allow to register the same struct platform_driver multiple
times.

Hence, register the imx_clk_scu_driver from module_init() and unregister
it in module_exit().

Note that we first register the imx8qxp_clk_driver and then call
imx_clk_scu_module_init() to avoid having to call
imx_clk_scu_module_exit() in the unwind path of imx8qxp_clk_init().

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 at ew.tq-group.com>
Closes: https://lore.kernel.org/lkml/13955113.uLZWGnKmhe@steina-w/
Tested-by: Alexander Stein <alexander.stein at ew.tq-group.com> # TQMa8x/MBa8x
Link: https://lore.kernel.org/lkml/DFU7CEPUSG9A.1KKGVW4HIPMSH@kernel.org/ [1]
Signed-off-by: Danilo Krummrich <dakr at kernel.org>
---
Changes in v2:
  - Expand commit message, mentioning a third bug fixed by this patch and noting
    the order of platform_driver_register() and imx_clk_scu_module_init() in
    imx8qxp_clk_init().
  - Rename imx8qxp_{init,exit} to imx8qxp_clk_{init,exit}.
  - Link to v1: https://lore.kernel.org/driver-core/20260211142321.55404-1-dakr@kernel.org/
---
 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..c781425a005e 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_clk_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_clk_init);
+
+static void __exit imx8qxp_clk_exit(void)
+{
+	imx_clk_scu_module_exit();
+	platform_driver_unregister(&imx8qxp_clk_driver);
+}
+module_exit(imx8qxp_clk_exit);
 
 MODULE_AUTHOR("Aisheng Dong <aisheng.dong at nxp.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
-- 
2.53.0