pca953x: Probing too early

[Fabio Estevam]

Adding the i2c-folks on Cc.

On Tue, Aug 20, 2024 at 5:02 PM Fabio Estevam <festevam at gmail.com> wrote:
>
> Hi,
>
> I am seeing an issue with the PCA935X driver in 6.6.41 and
> 6.11.0-rc4-next-20240820.
>
> The pca953x is getting probed before its I2C parent (i2c-2):
>
> [    1.872917] pca953x 2-0020: supply vcc not found, using dummy regulator
> [    1.889195] pca953x 2-0020: using no AI
> [    1.893260] pca953x 2-0020: failed writing register
> [    1.898258] pca953x 2-0020: probe with driver pca953x failed with error -11
> [    1.905575] i2c i2c-2: IMX I2C adapter registered
>
> This problem is seen on a custom imx8mp board.
> I am not able to reproduce it on an imx8mm-evk.
>
> If I select the pca953x as a module or insert a delay inside its
> probe() function, it probes successfully.
>
> The drivers/gpio/gpio-pca953x.c has the following comments:
>
> /* register after i2c postcore initcall and before
>  * subsys initcalls that may rely on these GPIOs
>  */
> subsys_initcall(pca953x_init);
>
> but it seems this is not happening.
>
> I have also tried to register it like this:
>
> --- a/drivers/gpio/gpio-pca953x.c
> +++ b/drivers/gpio/gpio-pca953x.c
> @@ -1369,21 +1369,7 @@ static struct i2c_driver pca953x_driver = {
>         .remove         = pca953x_remove,
>         .id_table       = pca953x_id,
>  };
> -
> -static int __init pca953x_init(void)
> -{
> -       return i2c_add_driver(&pca953x_driver);
> -}
> -/* register after i2c postcore initcall and before
> - * subsys initcalls that may rely on these GPIOs
> - */
> -subsys_initcall(pca953x_init);
> -
> -static void __exit pca953x_exit(void)
> -{
> -       i2c_del_driver(&pca953x_driver);
> -}
> -module_exit(pca953x_exit);
> +module_i2c_driver(pca953x_driver);
> )
>
> but this did not help either.
>
> Does anyone have any suggestions on how to fix this problem when the
> pca953x driver is built-in?

If I register the i2c-imx driver like this:

--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -1638,18 +1638,7 @@ static struct platform_driver i2c_imx_driver = {
        },
        .id_table = imx_i2c_devtype,
 };
-
-static int __init i2c_adap_imx_init(void)
-{
-       return platform_driver_register(&i2c_imx_driver);
-}
-subsys_initcall(i2c_adap_imx_init);
-
-static void __exit i2c_adap_imx_exit(void)
-{
-       platform_driver_unregister(&i2c_imx_driver);
-}
-module_exit(i2c_adap_imx_exit);
+module_platform_driver(i2c_imx_driver);

then the pca953x driver probes correctly.

:~/stable/linux$ git grep subsys_initcall drivers/i2c/ | wc -l
15

:~/stable/linux$ git grep module_platform_driver drivers/i2c/ | wc -l
75

Most of the I2C drivers are registered as module_platform_driver().