STM32MP1: Boot kernel via TFTP from U-Boot

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Today I just managed to boot kernel via TFTP on STM32MP1 board but steps I go through are quite different with i.MX8. Thus, I think there is a necessity to have a short note about this 🖋

Pre-requirements

  • TFTP server on PC is up and running(Check here)
  • Board and PC are in same LAN

TFTP folder

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~/data/srv/tftp$ tree
.
├── pxelinux.cfg
│   └── 01-e2-a4-06-a5-8f-7f
├── stm32mp157a-cp.dtb
└── uImage

1 directory, 3 files

U-Boot will use pxe command to load PXE configuration file from TFTP server(PC in my scenario). PXE configuration file has the same format with extlinux.conf, and the file name is related to hardware MAC address. In my case 01-e2-a4-06-a5-8f-7f:

  • 01: ARP type 1 for ethernet
  • e2-a4-06-a5-8f-7f: MAC address

Inside my PXE configuration file(01-e2-a4-06-a5-8f-7f):

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menu title Select the boot mode
 DEFAULT eMMC
 TIMEOUT 20
 LABEL initramfs
 	KERNEL uImage
 	FDT stm32mp157a-cp.dtb
 	INITRD uInitrd
 	APPEND rootwait rw earlyprintk console=ttySTM0,115200
 LABEL nfs
 	KERNEL uImage
 	FDT stm32mp157a-cp.dtb
 	APPEND root=/dev/nfs nfsroot=192.168.0.106:/nfsroot ip=dhcp rootwait rw earlyprintk console=ttySTM0,115200
 LABEL sdcard
 	KERNEL uImage
 	FDT stm32mp157a-cp.dtb
 	APPEND root=/dev/mmcblk0p6 rootwait rw earlyprintk console=ttySTM0,115200
 LABEL eMMC
 	KERNEL uImage
 	FDT stm32mp157a-cp.dtb
 	APPEND root=/dev/mmcblk1p6 rootwait rw earlyprintk console=ttySTM0,115200

With this configuration file we could choose in U-Boot where to load rootfs when booting.

U-Boot

After TFTP server and folder are ready, we can proceed on U-Boot. If CONFIG_NET_RANDOM_ETHADDR has not been set in uboot defconfig or MAC address haven’t been configured before, we might need to setup MAC address(ethaddr) manually. Meanwhile serverip need to be set as well:

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env set ethaddr e2:a4:06:a5:8f:7f
env set serverip 192.168.0.106
saveenv

After that we only need to run bootcmd_pxe if we want to load kernel from TFTP:

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Hit any key to stop autoboot:  0 
STM32MP> run bootcmd_pxe
ethernet@5800a000 Waiting for PHY auto negotiation to complete. done
BOOTP broadcast 1
DHCP client bound to address 192.168.0.101 (2 ms)
missing environment variable: pxeuuid
missing environment variable: bootfile
Retrieving file: pxelinux.cfg/01-e2-a4-06-a5-8f-7f
Using ethernet@5800a000 device
TFTP from server 192.168.0.106; our IP address is 192.168.0.101
Filename 'pxelinux.cfg/01-e2-a4-06-a5-8f-7f'.
Load address: 0xc4200000
Loading: #
         8.8 KiB/s
done
Bytes transferred = 608 (260 hex)
Config file found
Select the boot mode
1:      initramfs
2:      nfs
3:      sdcard
4:      eMMC
Enter choice: 4:        eMMC
missing environment variable: bootfile
Retrieving file: uImage
Using ethernet@5800a000 device
TFTP from server 192.168.0.106; our IP address is 192.168.0.101
Filename 'uImage'.
Load address: 0xc2000000
Loading: #################################################################
         #################################################################
         #################################################################
         ##################T ###############################################
         #################################################################
         #################################################################
         #################################################################
         #################################################################
         #################################################################
         #################################################################
         #################################################################
         #################################################################
         #################################################################
         #################################################################
         #################################################################
         #################################################################
         #################################################################
         #################################################################
         #################################################################
         ##############################################################
         265.6 KiB/s
done
Bytes transferred = 6640192 (655240 hex)
append: root=/dev/mmcblk1p6 rootwait rw earlyprintk console=ttySTM0,115200
missing environment variable: bootfile
Retrieving file: stm32mp157a-cp.dtb
Using ethernet@5800a000 device
TFTP from server 192.168.0.106; our IP address is 192.168.0.101
Filename 'stm32mp157a-cp.dtb'.
Load address: 0xc4000000
Loading: #############
         188.5 KiB/s
done
Bytes transferred = 62891 (f5ab hex)
## Booting kernel from Legacy Image at c2000000 ...
   Image Name:   Linux-4.19.49
   Created:      2019-06-09   7:17:25 UTC
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    6640128 Bytes = 6.3 MiB
   Load Address: c2000040
   Entry Point:  c2000040
   Verifying Checksum ... OK
## Flattened Device Tree blob at c4000000
   Booting using the fdt blob at 0xc4000000
   XIP Kernel Image ... OK
   Using Device Tree in place at c4000000, end c40125aa

Starting kernel ...

[    0.000000] Booting Linux on physical CPU 0x0
[    0.000000] Linux version 4.19.49 (oe-user@oe-host) (gcc version 8.2.0 (GCC)) #1 SMP PREEMPT Sun Jun 9
[    0.000000] CPU: ARMv7 Processor [410fc075] revision 5 (ARMv7), cr=10c5387d