am335x的emmc启动调试信息总线宽度为什么是4位？

=> mmc dev 0
switch to partitions #0, OK
mmc0 is current device
=> mmc info
Device: OMAP SD/MMC
Manufacturer ID: 82
OEM: 4a54
Name: NCardTran Speed: 50000000
Rd Block Len: 512
SD version 3.0
High Capacity: Yes
Capacity: 7.4 GiB
Bus Width: 4-bit
Erase Group Size: 512 Bytes
=> mmc dev 1
** First descriptor is NOT a primary desc on 1:1 **
switch to partitions #0, OK
mmc1(part 0) is current device
=> mmc info
Device: OMAP SD/MMC
Manufacturer ID: 11
OEM: 100
Name: 008G9Tran Speed: 52000000
Rd Block Len: 512
MMC version 4.5
High Capacity: Yes
Capacity: 7.3 GiB
Bus Width: 4-bit
Erase Group Size: 512 KiB
HC WP Group Size: 8 MiB
User Capacity: 7.3 GiB WRREL
Boot Capacity: 4 MiB ENH
RPMB Capacity: 512 KiB ENH

Jian Zhou：

应该是在u-boot阶段，工作在4线SD模式。