我使用的是一个BeagleBone板,默认的Debian映像会闪烁到内部emmc。
在设备启动时,我试图理解下面的U引导消息,尤其是它是如何报告mmc0 is current device的,然后是如何声明mmc1(part 0) is current device的。
这里发生了什么事?mmc0是内部的emmc内存还是SD卡,为什么引导加载程序要从mmc0切换到mmc1?
U-Boot SPL 2018.09-00002-g0b54a51eee (Sep 10 2018 - 19:41:39 -0500)
Trying to boot from MMC2
Loading Environment from EXT4...
** Unable to use mmc 0:1 for loading the env **
U-Boot 2018.09-00002-g0b54a51eee (Sep 10 2018 - 19:41:39 -0500), Build:
jenkins-github_Bootloader-Builder-65
CPU : AM335X-GP rev 2.1
I2C: ready
DRAM: 512 MiB
No match for driver 'omap_hsmmc'
No match for driver 'omap_hsmmc'
Some drivers were not found
Reset Source: Power-on reset has occurred.
RTC 32KCLK Source: External.
MMC: OMAP SD/MMC: 0, OMAP SD/MMC: 1
Loading Environment from EXT4...
** Unable to use mmc 0:1 for loading the env **
Board: BeagleBone Black
<ethaddr> not set. Validating first E-fuse MAC
BeagleBone Black:
Model: SeeedStudio BeagleBone Green Wireless:
BeagleBone: cape eeprom: i2c_probe: 0x54:
BeagleBone: cape eeprom: i2c_probe: 0x55:
BeagleBone: cape eeprom: i2c_probe: 0x56:
BeagleBone: cape eeprom: i2c_probe: 0x57:
Net: eth0: MII MODE
Could not get PHY for cpsw: addr 0
cpsw, usb_ether
Press SPACE to abort autoboot in 2 seconds
board_name=[A335BNLT] ...
board_rev=[GW1A] ...
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...
gpio: pin 56 (gpio 56) value is 0
gpio: pin 55 (gpio 55) value is 0
gpio: pin 54 (gpio 54) value is 0
gpio: pin 53 (gpio 53) value is 1
switch to partitions #0, OK
mmc0 is current device
gpio: pin 54 (gpio 54) value is 1
Checking for: /uEnv.txt ...
Checking for: /boot.scr ...
Checking for: /boot/boot.scr ...
Checking for: /boot/uEnv.txt ...
** Invalid partition 3 **
** Invalid partition 4 **
** Invalid partition 5 **
** Invalid partition 6 **
** Invalid partition 7 **
switch to partitions #0, OK
mmc1(part 0) is current device
Scanning mmc 1:1...
gpio: pin 56 (gpio 56) value is 0
gpio: pin 55 (gpio 55) value is 0
gpio: pin 54 (gpio 54) value is 0
gpio: pin 53 (gpio 53) value is 1
switch to partitions #0, OK
mmc1(part 0) is current device
gpio: pin 54 (gpio 54) value is 1
Checking for: /uEnv.txt ...
Checking for: /boot.scr ...
Checking for: /boot/boot.scr ...
Checking for: /boot/uEnv.txt ...
gpio: pin 55 (gpio 55) value is 1
2099 bytes read in 7 ms (292 KiB/s)
Loaded environment from /boot/uEnv.txt
Checking if uname_r is set in /boot/uEnv.txt...
gpio: pin 56 (gpio 56) value is 1
Running uname_boot ...
loading /boot/vmlinuz-4.14.71-ti-r80 ...
10416640 bytes read in 663 ms (15 MiB/s)发布于 2019-02-20 14:27:40
在这种情况下,mmc0是SD卡,mmc1是eMMC。“尝试从”引导“消息与SoC文档编号的设备匹配,从1开始编号,而后一条消息遵循正常约定,从0开始编号,这一点就不那么清楚了。
这个板上的默认引导命令将搜索多个位置以找到要引导的有效“东西”,这样用户就可以轻松地尝试其他的东西,它将查找SD卡(然后查找其上的位置),寻找要引导的东西,然后返回到eMMC。
https://unix.stackexchange.com/questions/501827
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