DE0-Nano-SoC, Strange error reading SD/MMC

I had similar issues, my SDcard was not picked up. Turns out its a device tree issue with MMC controller.

See here, looks like your prob too ... https://forum.rocketboards.org/t/linux-altera-4-12-failes-mmc-on-cyclonev-while-ltsi-does-not/1189

I added the following : CycloneV dts.

sdmmc_clk_divided: sdmmc_clk_divided {

#clock-cells = <0>;

compatible = "altr,socfpga-gate-clk";

clocks = <&sdmmc_clk>;

clk-gate = <0xa0 8>;

fixed-divider = <4>;

};

and changed my sdmmc rntry a bit to this :

hps_0_sdmmc: flash@0xff704000 {

compatible = "altr,socfpga-dw-mshc";

reg = <0xff704000 0x00001000>;

resets = <&hps_0_rstmgr SDMMC_RESET>;

interrupt-parent = <&hps_0_arm_gic_0>;

interrupts = <0 139 IRQ_TYPE_LEVEL_HIGH>;

//clocks = <&l4_mp_clk &sdmmc_clk>;

clocks = <&l4_mp_clk>, <&sdmmc_clk_divided>;

clock-names = "biu", "ciu";

fifo-depth = <1024>; /* embeddedsw.dts.params.fifo-depth type NUMBER */

#address-cells = <1>;

#size-cells = <0>;

status = "okay"; /* embeddedsw.dts.params.status type STRING */

broken-cd;

bus-width = <4>;

cap-mmc-highspeed;

cap-sd-highspeed;

}; //end flash@0xff704000 (hps_0_sdmmc)