As we know, the MMC0 interface of SAMA5D44 revA cannot be used for booting.
Does SAMA5D44 revB MMC0 interface can be used for booting? Would you recommend use MMC0 as boot-interface?
Our board HW configuration:
SOC: SAMA5D44
MMC0: eMMC5 (8 Bit width)
MMC1: WiFi Module
We had modified belows in AT91-Bootstrap and rebuilt it.
1. Set mmc0 in sama5d4_xplainedsd_uboot_secure_defconfig
2. Refer sama5d4ek.c and set PC4~PC13, PIOC, HSMCI0 in sama5d4_xplained.c
Do we miss anything?
We have no luck with booting from MMC0 even we rework eMMC5 to SDcard (4 Bit width).
Always stuck in Bootstrap ...

Please help us out ... Any help would be appreciated.
AT91Bootstrap 3.8.13 (Wed Nov 20 16:09:44 CST 2019)
All interrupts redirected to AIC
EEPROM: Loading AT24xx information ...
EEPROM: BoardName | [Revid] | VendorName
twi read: timeout to wait RXRDY bit on bus 0
EEPROM: Failed to read
EEPROM: Using default information
EEPROM: Board sn: 0x1012420 revision: 0x680820
ACT8865: Set REG1/REG2/REG3 Power-saving mode
twi read: timeout to wait RXRDY bit on bus 3
ACT8865: Disable ACT8865's I2C interface
[DBG] at91_mci0_hw_init
SD/MMC: Image: Read file u-boot.bin to 0x26f00000
[DBG] sdcard_identification()
[DBG] sd_cmd_go_idle_state() ret=0
[DBG] mmc_verify_operating_condition()
[DBG]: mmc_cmd_send_op_cond() ocr=0
[DBG] mmc_cmd_send_op_cond() ret=0
[DBG]: mmc_cmd_send_op_cond() ocr=1073741824
[DBG] mmc_cmd_send_op_cond()-try 0, ret=0
[DBG]: mmc_cmd_send_op_cond() ocr=1073741824
[DBG] mmc_cmd_send_op_cond()-try 1, ret=0
[DBG]: mmc_cmd_send_op_cond() ocr=1073741824
[DBG] mmc_cmd_send_op_cond()-try 2, ret=0
[DBG]: mmc_cmd_send_op_cond() ocr=1073741824
(...............Trying 1000 times)
Unusable Card
*** FATFS: f_open, filename: [u-boot.bin]: error
SD/MMC: Failed to load image