Boot EMMC¶
- Table of contents
- Boot EMMC
NOTE: The AM62x has multiple MMC interfaces. The EMMC is configured on MMC1
To boot the Dev Kit from EMMC using a CL supplied image, set the boot pins as follows:
| B9 | B8 | B7 | B6 | B5 | B4 | B3 |
| Port (0) | Reserved (0) | Fs/raw (1) | 1 | 0 | 0 | 1 |
Based on the TI wiki procedure ( https://software-dl.ti.com/processor-sdk-linux/esd/AM62X/08_03_00_19/exports/docs/linux/Foundational_Components/U-Boot/UG-Memory.html )
Major difference was the block size used. The TI wiki instructions assume a 512 byte block size. The U-Boot image we have was using 1024 byte block size and therefore programming the SPL and UBoot at wrong addresses.
EMMC Layout¶
boot0 partition (4 MB) user partition
0x0+----------------------------------+ 0x0+-------------------------+
| tiboot3.bin (512 KB) | | |
0x8000+----------------------------------+ | |
| tispl.bin (2 MB) | | |
0x280000+----------------------------------+ | rootfs |
| u-boot.img (1.412 MB) | | |
0x3E1000+----------------------------------+ | |
| environment (124 KB) | | |
0x400000+----------------------------------+ +-------------------------+
Steps¶
- generate 2 uuids (currently this must be done outside of u-boot... one needs to enable CONFIG_CMD_UUID if you want uuid generation in u-boot)
# Two possible options in linux $ uuidgen $ cat /proc/sys/kernel/random/uuid
- partition the eMMC device (can be done in u-boot as shown, or from linux using fdisk)
U-Boot # printenv partitions uuid_disk=${uuid_gpt_disk};name=rootfs,start=2MiB,size=-,uuid=${uuid_gpt_rootfs} U-Boot # setenv uuid_gpt_disk ...first uuid... U-Boot # setenv uuid_gpt_rootfs ...second uuid... U-Boot # gpt write mmc 0 ${partitions} /* <device num> is device index obtained from mmc list for eMMC */ U-Boot # reset /* required to reload partition data */
- Boot into linux from SD card
- Change dir to SD card boot partition
- enable writing to the mmbblk0boot0 partition
root@mitysom-am62x:~# echo 0 > /sys/block/mmcblk0boot0/force_ro
- Copy the needed images from the SD card to the eMMC boot partition
root@mitysom-am62x:~# dd if=tiboot3.bin of=/dev/mmcblk0boot0 bs=512 seek=0 root@mitysom-am62x:~# dd if=tispl.bin of=/dev/mmcblk0boot0 bs=512 seek=1024 root@mitysom-am62x:~# dd if=u-boot.img of=/dev/mmcblk0boot0 bs=512 seek=5120 Optional if you want to set the environment root@mitysom-am62x:~# dd if=<uboot env blob> of=/dev/mmcblk0boot0 bs=512 seek=7944
- Enable the boot partition of the eMMC device
From U-BootU-Boot # mmc partconf 0 1 1 1 U-Boot # mmc bootbus 0 2 0 0
OR from Linuxroot@mitysom-am62x:~# mmc bootpart enable 1 1 /dev/mmcblk0 root@mitysom-am62x:~# mmc bootbus set single_backward x1 x8 /dev/mmcblk0
- Set the boot mode to boot from the eMMC
BM0-7 = 11001xxx (SW1-4, SW1-7, SW-8 ON)
BM8-15 = 00000000
SW1-4-7 set the boot mode to eMMC
SW1-8 sets RAW mode
This will get you to U-Boot. To boot to linux, you need to install linux on the eMMC UDA partition (created above) and tell U-Boot to boot the OS from the eMMC.
The eMMC is MMC device 0 and we want the first partition of it
U-Boot # setenv mmcdev 0 U-Boot # setenv bootpart 0
One way to copy the linux rootfs...
Mount the SD card rootfs under /mnt and tar-copy it to the eMMC
root@mitysom-am62x:~# lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT ... mmcblk1 179:0 0 7.4G 0 disk |-mmcblk1p1 179:1 0 132.6M 0 part /run/media/mmcblk1p1 `-mmcblk1p2 179:2 0 3.3G 0 part / mmcblk0 179:32 0 59.3G 0 disk `-mmcblk0p1 179:33 0 59.3G 0 part /run/media/mmcblk0p1 mmcblk0boot0 179:64 0 31.5M 1 disk mmcblk0boot1 179:96 0 31.5M 1 disk root@mitysom-am62x:~# mkdir -p /mnt/sd-rootfs root@mitysom-am62x:~# mkdir -p /mnt/emmc-rootfs root@mitysom-am62x:~# mount /dev/mmcblk1p2 /mnt/sd-rootfs root@mitysom-em62x:~# umount /dev/mmcblk0p1 root@mitysom-am62x:~# mkfs.ext4 /dev/mmcblk0p1 mke2fs 1.45.7 (28-Jan-2021)
If there was an existing FS on the eMMC tell mkfs to erase it
/dev/mmcblk0p1 contains a ext3 file system labelled 'EMMC'
last mounted on /tmp/mnt_EMMC on Mon Jan 16 13:56:15 2023
Proceed anyway? (y,N) y
Discarding device blocks: done
Creating filesystem with 15540096 4k blocks and 3891200 inodes
Filesystem UUID: f6975435-0bd3-425d-b2eb-57cd2c3eaaf2
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000, 7962624, 11239424
Allocating group tables: done
Writing inode tables: done
Creating journal (65536 blocks): done
Writing superblocks and filesystem accounting information: done
root@mitysom-am62x:~# mount /dev/mmcblk0p1 /mnt/emmc-rootfs/
root@mitysom-am62x:~# tar -C /mnt/sd-rootfs/ -cf - . |tar -C /mnt/emmc-rootfs/ -xf -
Note: If U-Boot fails to boot the SD card, it will automatically try to boot from eMMC. To force U-Boot to use the filesystem on the eMMC, simply remove the SD card.
Hardware Reset setting¶
NOTE: We enable hw reset in our factory test environment, setting this yourself should not be necessary.
The eMMC part ships with hardware reset disabled. This caused reset/reboot to hang when booting from the eMMC.
To fix this, the HW reset needs to be enabled in the part. This is done by writing a 1 to the RST_N_FUNCTION CSD register in the part.
THIS IS A ONE-TIME-PROGRAMMABLE VALUE
If you write a 2 to this register, you will permanently DISABLE reset and effectively prevent using the eMMC as a boot device.
From linux¶
root@mitysom-am62x:~# mmc hwreset enable /dev/mmcblk0
The state of this register can be checked using the extcsd read command
root@mitysom-am62x:~# mmc extcsd read /dev/mmcblk0 | grep RST H/W reset function [RST_N_FUNCTION]: 0x01
From U-Boot¶
mmc rst-function 0 1
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