How do I implement SDIO reset in ST60/SU60?

SDIO reset would rely on SDIO card detection function, which can be done by broken-cd setting in device tree.

1. Modify the dts file:

For example if you use NXP IMX6UL board, the dts file is located at “~/projects/fsl-release-bsp/build-imx6ul-fb/tmp/work-shared/imx6ulevk/kernel-source/arch/arm/boot/dts/imx6ul-14x14-evk.dts”. If you use mmc0, the setting will be in usdhc1.

Add broken-cd function in the setting of usdhc1 as below and also need to make sure there is no setting of “non-removable”.

&usdhc1 {

pinctrl-names = "default", "state_100mhz", "state_200mhz";

pinctrl-0 = <&pinctrl_usdhc1>;

pinctrl-1 = <&pinctrl_usdhc1_100mhz>;

pinctrl-2 = <&pinctrl_usdhc1_200mhz>;

cd-gpios = <&gpio1 19 GPIO_ACTIVE_LOW>;

keep-power-in-suspend;

broken-cd;

enable-sdio-wakeup;

vmmc-supply = <&reg_sd1_vmmc>;

status = "okay";

};

2. Rebuild kernel and then it will set MMC_CAP_NEEDS_POLL during mmc driver initialization.

int mmc_of_parse(struct mmc_host *host)

{

…

if (of_property_read_bool(np, "non-removable")) {

dev_warn(host->parent,"Parse Card Detection: non-removable\n");

host->caps |= MMC_CAP_NONREMOVABLE;

if (of_property_read_bool(np, "cd-post"))

host->caps2 |= MMC_CAP2_CD_POST;

} else {

cd_cap_invert = of_property_read_bool(np, "cd-inverted");

if (of_property_read_bool(np, "broken-cd"))

{

dev_info(host->parent,"Parse Card Detection: broken-cd\n");

host->caps |= MMC_CAP_NEEDS_POLL;

}

…

}

…

}

Then SDHC will check the SDIO bus per second and once there is any PMU_EN or PDN assert event, SDHC will detect the bus no longer available and will unload/reload the SDIO again automatically.