记录 dts 里面添加 SD cd

// dts 
741 &mmc1 {
742     vmmc-supply = <&vmmcsd_fixed>;
743     status = "okay";
744     bus-width = <0x4>;
745     pinctrl-names = "default";
746     pinctrl-0 = <&mmc1_pins>;
747     cd-gpios = <&gpio2 1 GPIO_ACTIVE_LOW>;      // ti am335x 里面增加片选
748 };

200             0x8c (PIN_INPUT | MUX_MODE7)    /* gpmc_clk.gpio2_1  sd_cs */
//  pin mux 里面定义为 gpio