How to disable in the device tree sdmmc3

Technical Support
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1

I need to configure 190 pin (sdmmc3_cd_n_pv2) as out. In the file tegra124-apalis-pinmux.dtsi removed the settings of the pins

sdmmc3_clk_pa6, sdmmc3_cmd_pa7 sdmmc3_dat3_pb4,sdmmc3_dat2_pb5, 
sdmmc3_dat1_pb6, sdmmc3_dat0_pb7, sdmmc3_clk_lb_in_pee5, sdmmc3_clk_lb_out_pee4

and set sdmmc3_cd_n_pv2 as follows:

sdmmc3_cd_n_pv2 { // CD# GPIO 
    				nvidia,pins = "sdmmc3_cd_n_pv2";
    				nvidia,function = "rsvd3";
    				/*nvidia,pull = <TEGRA_PIN_PULL_UP>;
    				nvidia,tristate = <TEGRA_PIN_ENABLE>;
    				nvidia,enable-input = <TEGRA_PIN_ENABLE>;*/
    				nvidia,pull = <TEGRA_PIN_PULL_NONE>;
    				nvidia,tristate = <TEGRA_PIN_DISABLE>;
    				nvidia,enable-input = <TEGRA_PIN_DISABLE>;
    			};

In the file tegra124-apalis-gpio.dtsi I add this pin to the group gpio-output-high:

TEGRA_GPIO(V, 2)

I compile device tree and install firmware.
But,

echo 170 > /sys/class/gpio/export
-sh: echo: write error: Device or resource busy

What am I doing wrong?

2

You would also need to make sure the SDMMC3 SDHCI controller instance is not initialised. In the downstream Linux kernel which is only partially device tree enabled this would still have to be done in the platform data by e.g. commenting the following. Please note that device2 refers to SDMMC3 as they start their numbering with zero rather than NVIDIA starting with one.