gpio: omap: do not register driver in probe()

Commit 11a78b794496 ("ARM: OMAP: MPUIO wake updates") registers the
omap_mpuio_driver from omap_mpuio_init(), which is called from
omap_gpio_probe().

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 potential deadlock
condition described in [1].

Additionally, the omap_mpuio_driver is never unregistered from the
driver core, even if the module is unloaded.

Hence, register the omap_mpuio_driver from the module initcall and
unregister it in module_exit().

Link: https://lore.kernel.org/lkml/[e-mail]/ [1]
Fixes: dc23806a7c47 ("driver core: enforce device_lock for driver_match_device()")
Fixes: 11a78b794496 ("ARM: OMAP: MPUIO wake updates")
Reviewed-by: Greg Kroah-Hartman <[e-mail]>
Signed-off-by: Danilo Krummrich <[e-mail]>
Reviewed-by: Rafael J. Wysocki (Intel) <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Bartosz Golaszewski <[e-mail]>

drivers/gpio/gpio-omap.c

···
 
 static inline void omap_mpuio_init(struct gpio_bank *bank)
 {
-	platform_set_drvdata(&omap_mpuio_device, bank);
+	static bool registered;
 
-	if (platform_driver_register(&omap_mpuio_driver) == 0)
-		(void) platform_device_register(&omap_mpuio_device);
+	platform_set_drvdata(&omap_mpuio_device, bank);
+	if (!registered) {
+		(void)platform_device_register(&omap_mpuio_device);
+		registered = true;
+	}
 }
 
 /*---------------------------------------------------------------------*/
···
  */
 static int __init omap_gpio_drv_reg(void)
 {
-	return platform_driver_register(&omap_gpio_driver);
+	int ret;
+
+	ret = platform_driver_register(&omap_mpuio_driver);
+	if (ret)
+		return ret;
+
+	ret = platform_driver_register(&omap_gpio_driver);
+	if (ret)
+		platform_driver_unregister(&omap_mpuio_driver);
+
+	return ret;
 }
 postcore_initcall(omap_gpio_drv_reg);
 
 static void __exit omap_gpio_exit(void)
 {
 	platform_driver_unregister(&omap_gpio_driver);
+	platform_driver_unregister(&omap_mpuio_driver);
 }
 module_exit(omap_gpio_exit);