Symptoms
When configure a gpio pin for a driver in the dts/dtsi file like below example,
e.g.
a-switch {
compatible = "a-switch-driver";
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_switch>;
gpios = <&lsio_gpio1 1 GPIO_ACTIVE_HIGH>;
status = "okay";
};
pinctrl_switch: switch_gpio {
fsl,pins = < IMX8QXP_SPI2_SDO_LSIO_GPIO1_IO01 0x21 >;
};
then you may get the error when request the gpio in the driver during the kernel boot up.
Error message like this:
a-switch: failed to request gpio
a-switch: probe of a-switch failed with error -22
Linux version: L5.4.x
Diagnosis
Because the gpio_mxc_init function run before the function imx_scu_driver_init. The pm_domains for gpio is not ready before running mxc_gpio_probe, so gpio request will be failed.
Solution
There are two ways to resolve this issue
1. Build the driver as a module. i.e. select the driver in kernel’s menuconfig as “M”. Then , run “insmod” to load the driver after the kernel boot up.
OR
2. Apply below patch, let gpio driver init after scu driver.
diff --git a/drivers/gpio/gpio-mxc.c b/drivers/gpio/gpio-mxc.c
index 1dfe513f8fcf..52b5799040b3 100644
--- a/drivers/gpio/gpio-mxc.c
+++ b/drivers/gpio/gpio-mxc.c
@@ -892,7 +892,7 @@ static int __init gpio_mxc_init(void)
return platform_driver_register(&mxc_gpio_driver);
}
-subsys_initcall(gpio_mxc_init);
+device_initcall(gpio_mxc_init);
