How to deal with VIO_SD of W8997 when using sdio SDR104 connect to imx8mp's sdhc2?

[changbaoma]

we know imx8mp's NVCC_SD2 of sdhc2 can auto switch voltage 1.8v and 3.3v accroding to Speed Mode(DS/HS or UHS).

1. we notice that VIO_SD pin of W8997 can supply 1.8V or 3.3V, but we don't know how to choose the voltage correctly?

2. Is it necessary to make VIO_SD voltage follow NVCC_SD2 voltage? eg. connect NVCC_SD2 to  VIO_SD directly.

3. How about this situation that if our hardwre already fixed 1.8V power supply to VIO_SD?  can SDR104 work?

[estephania_mart · Accepted solution]

Hello,

1.- 

The SD2 IO voltage NVCC_SD2 of I.MX8MP is output by LDO5 of PCA9450, and it outputs 3.3V or 1.8V. SD_VSEL pin of LDO5: when LOW, LDO5 outputs 3.3V; when HIGH, LDO5 outputs 1.8V.

In this case, you only need to control the level of SD_VSEL of PCA9450.

2.
To set it, you will need to enter to the dts directory, find the imx8mm-evk-usd-wifi.dts file, refer to this file and add such a file to the 8mp-evk board.

Through the following code, you can see that the output is 1.8V by default:

&usdhc2 {
pinctrl-assert-gpios = <&gpio1 4 GPIO_ACTIVE_HIGH>;
/delete-property/ cd-gpios;
pm-ignore-notify;
keep-power-in-suspend;
non-removable;
cap-power-off-card;
};

3.
The VIO_SD of the wifi terminal must use 1.8V, otherwise, there is no way to use the 2000MHz speed.

Regards