Output of u-boot with my complied sd card image:

U-Boot SPL 2023.07-rc6-ge64596af4c-dirty (Oct 20 2025 - 21:45:58 -0400)
DDRCAL: Scrubbing ECC RAM (1024 MiB).
DDRCAL: SDRAM-ECC initialized success with 608 ms
MPU           800000 kHz
DDR           400000 kHz
EOSC1          25000 kHz
EOSC2          25000 kHz
F2S_SDR_REF        0 kHz
F2S_PER_REF        0 kHz
MMC            50000 kHz
QSPI          400000 kHz
UART          100000 kHz
SPI           200000 kHz
Trying to boot from MMC1


U-Boot 2023.07-rc6-ge64596af4c-dirty (Oct 20 2025 - 21:45:58 -0400) Critical Link MitySOM-5CSx

CPU:   Altera SoCFPGA Platform
FPGA:  Altera Cyclone V, SE/A6 or SX/C6 or ST/D6, version 0x0
BOOT:  SD/MMC Internal Transceiver (3.0V)
DRAM:  1 GiB
Core:  35 devices, 19 uclasses, devicetree: separate
MMC:   dwmmc0@ff704000: 0
Loading Environment from MMC... OK
In:    serial
Out:   serial
Err:   serial
Model: MitySOM-5CSX-H6-42A Altera SOCFPGA Cyclone V
BOARD: Critical Link MitySOM-5CSx Module
Net:   eth0: ethernet@ff702000
gpio: pin 0 (gpio 0) value is 1
Hit any key to stop autoboot:  0
MitySOM-5CSx #


output of u-boot with the provided sd card image.

U-Boot SPL 2013.01.01 (Oct 19 2023 - 21:49:03)
BOARD : Critical Link MitySOM-5CSx Module
CLOCK: EOSC1 clock 25000 KHz
CLOCK: EOSC2 clock 25000 KHz
CLOCK: F2S_SDR_REF clock 0 KHz
CLOCK: F2S_PER_REF clock 0 KHz
CLOCK: MPU clock 800 MHz
CLOCK: DDR clock 400 MHz
CLOCK: UART clock 100000 KHz
CLOCK: MMC clock 50000 KHz
CLOCK: QSPI clock 400000 KHz
RESET: COLD
SDRAM: Initializing MMR registers
SDRAM: Calibrating PHY
SEQ.C: Preparing to start memory calibration
SEQ.C: CALIBRATION PASSED
SDRAM: 1024 MiB
SDRAM: Initializing SDRAM ECC
SDRAM: ECC initialized successfully with 1511 ms
SDRAM: ECC Enabled
ALTERA DWMMC: 0


U-Boot 2013.01.01 (Oct 19 2023 - 21:49:22) Critical Link MitySOM-5CSx

CPU   : Altera SOCFPGA Platform
BOARD : Critical Link MitySOM-5CSx Module
I2C:   ready
DRAM:  1 GiB
MMC:   ALTERA DWMMC: 0
In:    serial
Out:   serial
Err:   serial
Net:   mii0
gpio: pin 0 (bank/mask = 0/0x00000001)
gpio: pin 0 (gpio 0) value is 1
Hit any key to stop autoboot:  0
MitySOM-5CSx #