Hi Levin,

Am Dienstag, 31. Juli 2018, 07:59:22 CEST schrieb djw at t-chip.com.cn:

From: Levin Du <redacted>

In roc-rk3328-cc board, the signal voltage of sdmmc is supplied by the
vcc_sdio regulator, which is a mux between 1.8V and 3.3V, controlled by
a special output only gpio pin labeled "gpiomut_pmuio_iout",
corresponding bit 1 of the syscon GRF_SOC_CON10.

This special pin can now be reference as <&grf_gpio 0>, thanks to the
gpio-syscon driver, which makes writing regulator-gpio possible.

If the signal voltage changes, the io domain needs to change
correspondingly.

To use this feature, the following options are required in kernel config:
 - CONFIG_GPIO_SYSCON=y
 - CONFIG_POWER_AVS=y
 - CONFIG_ROCKCHIP_IODOMAIN=y

Signed-off-by: Levin Du <redacted>

[...]

applied to my dts64 branch after dropping the grf_gpio enablement,
see comment in patch2 regarding the always present pin.


Thanks
Heiko