问题描述
我正在学习Mastering Embedded Linux Programming第二版
看不到u-boot提示（U-Boot＃）
我使用了u-boot v2020.07，crosstool-ng v1.24.0，并将MLO，u-boot.img复制到了SD卡。
我该如何解决这个问题？
谢谢。
U-Boot SPL 2020.07 (Oct 21 2020 - 13:46:52 +0900)
Trying to boot from MMC1
U-Boot 2020.07 (Oct 21 2020 - 13:46:52 +0900)
cpu : AM335X-GP rev 2.1
Model: TI AM335x BeagleBone Black
DRAM: 512 MiB
WDT: Started with servicing (60s timeout)
NAND: 0 MiB
MMC: OMAP SD/MMC: 0,OMAP SD/MMC: 1
Loading Environment from FAT... *** Warning - bad CRC,using default environment
<ethaddr> not set. Validating first E-fuse MAC
Net: eth0: ethernet@4a100000
Warning: usb_ether MAC addresses don't match:
Address in ROM is de:ad:be:ef:00:01
Address in environment is d0:5f:b8:d1:0b:69,eth1: usb_ether
Hit any key to stop autoboot: 0
switch to partitions #0,OK
mmc0 is current device
SD/MMC found on device 0
switch to partitions #0,OK
mmc0 is current device
Scanning mmc 0:1...
switch to partitions #0,OK
mmc1(part 0) is current device
Scanning mmc 1:1...
switch to partitions #0,OK
mmc1(part 0) is current device
SD/MMC found on device 1
Error: "bootcmd_nand0" not defined
starting USB...
Bus usb@47401800: Port not available.
ethernet@4a100000 Waiting for PHY auto negotiation to complete......... TIMEOUT !
using musb-hdrc,OUT ep1out IN ep1in STATUS ep2in
MAC de:ad:be:ef:00:01
HOST MAC de:ad:be:ef:00:00
RNdis ready
missing environment variable: pxeuuid
Retrieving file: pxelinux.cfg/01-d0-5f-b8-d1-0b-67
ethernet@4a100000 Waiting for PHY auto negotiation to complete......... TIMEOUT !
Warning: usb_ether MAC addresses don't match:
Address in ROM is de:ad:be:ef:00:01
Address in environment is d0:5f:b8:d1:0b:69
using musb-hdrc,OUT ep1out IN ep1in STATUS ep2in
MAC de:ad:be:ef:00:01
HOST MAC de:ad:be:ef:00:00
RNdis ready
Retrieving file: pxelinux.cfg/00000000
ethernet@4a100000 Waiting for PHY auto negotiation to complete......... TIMEOUT !
Warning: usb_ether MAC addresses don't match:
Address in ROM is de:ad:be:ef:00:01
Address in environment is d0:5f:b8:d1:0b:69
using musb-hdrc,OUT ep1out IN ep1in STATUS ep2in
MAC de:ad:be:ef:00:01
HOST MAC de:ad:be:ef:00:00
RNdis ready
Retrieving file: pxelinux.cfg/0000000
ethernet@4a100000 Waiting for PHY auto negotiation to complete......... TIMEOUT !
Warning: usb_ether MAC addresses don't match:
Address in ROM is de:ad:be:ef:00:01
Address in environment is d0:5f:b8:d1:0b:69
using musb-hdrc,OUT ep1out IN ep1in STATUS ep2in
MAC de:ad:be:ef:00:01
HOST MAC de:ad:be:ef:00:00
RNdis ready
Retrieving file: pxelinux.cfg/000000
ethernet@4a100000 Waiting for PHY auto negotiation to complete......... TIMEOUT !
Warning: usb_ether MAC addresses don't match:
Address in ROM is de:ad:be:ef:00:01
Address in environment is d0:5f:b8:d1:0b:69
using musb-hdrc,OUT ep1out IN ep1in STATUS ep2in
MAC de:ad:be:ef:00:01
HOST MAC de:ad:be:ef:00:00
RNdis ready
Retrieving file: pxelinux.cfg/00000
ethernet@4a100000 Waiting for PHY auto negotiation to complete......... TIMEOUT !
Warning: usb_ether MAC addresses don't match:
Address in ROM is de:ad:be:ef:00:01
Address in environment is d0:5f:b8:d1:0b:69
using musb-hdrc,OUT ep1out IN ep1in STATUS ep2in
MAC de:ad:be:ef:00:01
HOST MAC de:ad:be:ef:00:00
RNdis ready
Retrieving file: pxelinux.cfg/0000
ethernet@4a100000 Waiting for PHY auto negotiation to complete......... TIMEOUT !
Warning: usb_ether MAC addresses don't match:
Address in ROM is de:ad:be:ef:00:01
Address in environment is d0:5f:b8:d1:0b:69
using musb-hdrc,OUT ep1out IN ep1in STATUS ep2in
MAC de:ad:be:ef:00:01
HOST MAC de:ad:be:ef:00:00
RNdis ready
Retrieving file: pxelinux.cfg/000
ethernet@4a100000 Waiting for PHY auto negotiation to complete......... TIMEOUT !
Warning: usb_ether MAC addresses don't match:
Address in ROM is de:ad:be:ef:00:01
Address in environment is d0:5f:b8:d1:0b:69
using musb-hdrc,OUT ep1out IN ep1in STATUS ep2in
MAC de:ad:be:ef:00:01
HOST MAC de:ad:be:ef:00:00
RNdis ready
Retrieving file: pxelinux.cfg/00
ethernet@4a100000 Waiting for PHY auto negotiation to complete......... TIMEOUT !
Warning: usb_ether MAC addresses don't match:
Address in ROM is de:ad:be:ef:00:01
Address in environment is d0:5f:b8:d1:0b:69
using musb-hdrc,OUT ep1out IN ep1in STATUS ep2in
MAC de:ad:be:ef:00:01
HOST MAC de:ad:be:ef:00:00
RNdis ready
Retrieving file: pxelinux.cfg/0
ethernet@4a100000 Waiting for PHY auto negotiation to complete......... TIMEOUT !
Warning: usb_ether MAC addresses don't match:
Address in ROM is de:ad:be:ef:00:01
Address in environment is d0:5f:b8:d1:0b:69
using musb-hdrc,OUT ep1out IN ep1in STATUS ep2in
MAC de:ad:be:ef:00:01
HOST MAC de:ad:be:ef:00:00
RNdis ready
Retrieving file: pxelinux.cfg/default-arm-am33xx-am335x
ethernet@4a100000 Waiting for PHY auto negotiation to complete......... TIMEOUT !
Warning: usb_ether MAC addresses don't match:
Address in ROM is de:ad:be:ef:00:01
Address in environment is d0:5f:b8:d1:0b:69
using musb-hdrc,OUT ep1out IN ep1in STATUS ep2in
MAC de:ad:be:ef:00:01
HOST MAC de:ad:be:ef:00:00
RNdis ready
Retrieving file: pxelinux.cfg/default-arm-am33xx
ethernet@4a100000 Waiting for PHY auto negotiation to complete......... TIMEOUT !
Warning: usb_ether MAC addresses don't match:
Address in ROM is de:ad:be:ef:00:01
Address in environment is d0:5f:b8:d1:0b:69
using musb-hdrc,OUT ep1out IN ep1in STATUS ep2in
MAC de:ad:be:ef:00:01
HOST MAC de:ad:be:ef:00:00
RNdis ready
Retrieving file: pxelinux.cfg/default-arm
ethernet@4a100000 Waiting for PHY auto negotiation to complete......... TIMEOUT !
Warning: usb_ether MAC addresses don't match:
Address in ROM is de:ad:be:ef:00:01
Address in environment is d0:5f:b8:d1:0b:69
using musb-hdrc,OUT ep1out IN ep1in STATUS ep2in
MAC de:ad:be:ef:00:01
HOST MAC de:ad:be:ef:00:00
RNdis ready
Retrieving file: pxelinux.cfg/default
ethernet@4a100000 Waiting for PHY auto negotiation to complete......... TIMEOUT !
Warning: usb_ether MAC addresses don't match:
Address in ROM is de:ad:be:ef:00:01
Address in environment is d0:5f:b8:d1:0b:69
using musb-hdrc,OUT ep1out IN ep1in STATUS ep2in
MAC de:ad:be:ef:00:01
HOST MAC de:ad:be:ef:00:00
RNdis ready
Config file not found
starting USB...
Bus usb@47401800: Port not available.
ethernet@4a100000 Waiting for PHY auto negotiation to complete......... TIMEOUT !
Warning: usb_ether MAC addresses don't match:
Address in ROM is de:ad:be:ef:00:01
Address in environment is d0:5f:b8:d1:0b:69
using musb-hdrc,OUT ep1out IN ep1in STATUS ep2in
MAC de:ad:be:ef:00:01
HOST MAC de:ad:be:ef:00:00
RNdis ready
ethernet@4a100000 Waiting for PHY auto negotiation to complete......... TIMEOUT !
Warning: usb_ether MAC addresses don't match:
Address in ROM is de:ad:be:ef:00:01
Address in environment is d0:5f:b8:d1:0b:69
using musb-hdrc,OUT ep1out IN ep1in STATUS ep2in
MAC de:ad:be:ef:00:01
HOST MAC de:ad:be:ef:00:00
RNdis ready
=>
解决方法
这可能是因为您收到的提示是您所期望的，但是您确实从u-boot收到了提示，即发布的输出中的最后一个=>。
如果输入help，然后按Enter，则应该获得可用命令的列表。
这本书已经有5年历史了，您正在使用u-boot 2020.07，这也许可以解释这一差异。
作者可能还已经在自己编译的u-boot中自定义了提示消息：您可以通过在您使用的配置文件的CONFIG_SYS_PROMPT符号定义中添加一个添加/修改值来完成此操作，说configs/am335x_evm_defconfig
CONFIG_SYS_PROMPT="U-Boot# "
重新编译了u-boot之后，您应该会得到准确的提示消息。