mounting SD Card on uClinux

I am having a similar problem using the SPI(3-wire) IP core and uClinux. I am using DE2-115 board and tried with 4 different cards (nothing changed), also same output when using no card at all. I am using "nios2"-branch (uClinux 3.7.0+), but have tried with "v3.3-nios2 -> v3.6-nios2" with same results.

mmc_spi spi32766.0: setup mode 0, 8 bits/w, 400000 Hz max --> 0
mmc0: req done (CMD58): 0: 00000000 00000000 00000000 00000000
mmc0: host doesn't support card's voltages
mmc0: error -22 whilst initialising SD card

My dts is configured as follows:

                mmc_spi: spi <at> 0x10003420 {
                        compatible = "ALTR,spi-12.0", "ALTR,spi-1.0";
                        reg = < 0x10003420 0x00000020 >;
                        interrupt-parent = < &cpu >;
                        interrupts = < 2 >;
                        mmc-slot <at> 0 {
                                compatible = "mmc-spi-slot";
                                reg = < 0x00000000 >;
                                voltage-ranges = <3300 3300>;
                                spi-max-frequency = <2000000>;
                        };
                };

I have really checked all the wire connections multiple times. They are connected as follows:

SD_DAT --> MISO
SD_CMD <-- MOSI
SD_CLK <-- SCLK
SD_DAT <-- SS_N

Any hints or suggestions on what I am doing wrong is appreciated. Thank you.