I am interfacing an external WiFi module card supporting SDIO 3.0 with IMX6SLL-EVK host platform.
IMX6SLL-EVK host is running u-boot-2008.01 & Linux kernel 4.9.11.
The SDIO port used is uSDHC3. The WIFI card is inserted with 1.8v operation settings.
When the WiFi card is inserted into the uSDHC3 slot, the MMC initialization tuning starts at 3.3v and some times its reaching 1.8v. sometimes it causes MMC handshake failure and MMC timeout crash.
To avoid this the uSDHC3 port should be starting with 1.8v SDIO signal settings.
I am trying to set the register value uSDHC3_VEND_SPEC.VSELECT to 1.
Where should it be done? Either in u-boot or kernel?
what are the device tree settings needed for uSDHC3 in iMX6SLL-EVK.dts file?
If it can be done in kernel, pls guide me @@to set this value.