From mboxrd@z Thu Jan  1 00:00:00 1970
From: jags gediya <jags.gediya@gmail.com>
Subject: WiFi card through sdio interface in kernel 3.10.17
Date: Tue, 1 Jul 2014 18:57:54 +0530
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Hi all,

I am using linux kernel 3.10.17. I  have interfaced wifi module from
TI to sdio interface.
I am getting following error in kernel logs

mmc0: Switching to 3.3V signaling voltage failed

i have done following configuration in device tree.

reg_3p3v: 3p3v {
            compatible = "regulator-fixed";
            regulator-name = "3P3V";
            regulator-min-microvolt = <3300000>;
            regulator-max-microvolt = <3300000>;
            regulator-always-on;
            };

        wilink_wl_en: tiwi_wlan {
            compatible = "regulator-fixed";
            regulator-name = "wilink_wl_en";
            regulator-min-microvolt = <1800000>;
            regulator-max-microvolt = <1800000>;
            gpio = <&gpio1 12 0>;
            startup-delay-us = <70000>;
            enable-active-high;
        };

and for usdhc1,


&usdhc1 {
    pinctrl-names = "default";
    pinctrl-0 = <&pinctrl_usdhc1_1>;
    bus-width = <4>;
    non-removable;
    vmmc-supply = <&reg_3p3v>;
    vqmmc-supply = <&wilink_wl_en>;
    ocr-limit = <0x80>;
    power-off-card;
    keep-power-in-suspend;
    status = "okay";
};

What can be the reason of error
mmc0: Switching to 3.3V signaling voltage failed?