Storage layout | ConnectCore MP15

The ConnectCore MP15 uses a NAND flash as main storage media. The flash is divided into logical partitions per the U-Boot variable mtdparts, which contains a string in the format described by the Linux kernel parameters in drivers/mtd/parsers/cmdlinepart.c.

Partition table

The default NAND partition table on the ConnectCore MP15 establishes the following partitions:

NAND flash layout for dual boot

fsbl1, fsbl2: FSBL stands for First Stage Bootloader. These partitions contain (in duplicate) the ARM Trusted Firmware (TF-A), which is the first piece of firmware that runs after the ROM loader. Its primary purpose is to perform any additional initialization required to load and authenticate all third-level firmware images into their executable RAM locations.

Partitions are redundant. If the ROM loader cannot boot from fsbl1, it will fall back to boot from fsbl2.
metadata1, metadata2: These partitions are currently not used.
fip-a, fip-b: FIP stands for Firmware Image Package. These partitions contain a FIP image that contains the Trusted Execution Environment (TEE) firmware and the U-Boot bootloader.

Partitions are redundant. If the TF-A cannot boot from fip-a, it will fall back to boot from fip-b.
UBI: This is a relatively small partition that contains UBI volumes for the U-Boot environment and the Linux kernel and device trees.
UBI_2: This partition extends to all the remaining space and contains UBI volumes for the Linux rootfs.

U-Boot requires less time to attach UBI to a small partition than to a large one, so the main area of the NAND is comprised of two partitions. This results in a faster boot time than if only one partition occupies the whole NAND.

If you are transitioning from previous firmware where the partition table only had one UBI partition (dey-4.0-r3 or older), refer to Migrate to the new partition table for instructions on how to re-format the NAND to the new partition table.

Dual boot UBI volumes (default)

The ConnectCore MP15 enables Dual boot by default. On a dual boot-enabled system the UBI and UBI_2 partitions contain the following UBI volumes:

NAND flash layout for dual boot

UBI partition
- uboot_config, uboot_config_r: (UBI volumes) Contain the U-Boot environment and its redundant copy.
- linux_a: (UBI volume) Contains the Linux kernel, device tree files, and U-Boot boot scripts. U-Boot reads the operating system files from this default volume.
- linux_b: (UBI volume) Same as linux_a (for system B).
UBI_2 partition
- rootfs_a: (UBI volume) Linux root file system volume (for system A)
- rootfs_b: (UBI volume) Linux root file system volume (for system B)
- data: Placeholder volume for user data.

Single system UBI volumes

When the NAND capacity doesn’t allow for a dual boot UBI volumes layout, you can alternatively define a single system UBI volumes layout:

NAND flash layout

UBI partition
- uboot_config, uboot_config_r: (UBI volumes) Contain the U-Boot environment and its redundant copy.
- linux: (UBI volume) Contains the Linux kernel, device tree files, and U-Boot boot scripts. U-Boot reads the operating system files from this default volume.
- recovery: (UBI volume) Contains a Linux kernel, device tree files, U-Boot boot scripts, and a recovery ramdisk image that can be launched (instead of the default operating system) to perform firmware updates on the device.
UBI_2 partition
- rootfs: (UBI volume) Contains the Linux root file system.
- update: (UBI volume) Placeholder volume to store firmware update files prior to launching a firmware update process on the device.
- data: Placeholder volume for user data.

Change NAND layout

From dual boot to single system

To prepare your NAND for single system UBI volumes, run the following in U-Boot:

=> setenv dualboot no
=> run ubivolscript
=> saveenv

From single system to dual boot

To prepare your NAND for dual boot UBI volumes, run the following in U-Boot:

=> setenv dualboot yes
=> run ubivolscript
=> saveenv

Migrate to the new partition table

If your SOM has a U-Boot v2021.10-r3 or older, your NAND partition table only has one UBI partition with UBI volumes for all system partitions. Starting from dey-4.0-r4 and U-Boot v2021.10-r4, the partition table has been reworked to contain two partitions (UBI and UBI_2), as explained in Partition table.

The following instructions show how to re-format the NAND to the new partition table layout. If your system already has these two partitions, you can skip this procedure.

Re-format partition table (click to expand)

The following procedure will destroy existing data in the NAND.

Update the fip-a/fip-b partitions with the latest available FIP image (or one built by you based on dey-4.0-r4 or newer).
Restart the device to boot with the new U-Boot. U-Boot complains that it cannot attach the UBI partition to read the environment.
Run env default -a to set the new U-Boot default environment.

Run mtdparts to verify the new partition table contains both UBI and UBI_2 partitions:

=> mtdparts
device nand0 <nand0>, # parts = 8
 #: name                size            offset          mask_flags
 0: fsbl1               0x00080000      0x00000000      0
 1: fsbl2               0x00080000      0x00080000      0
 2: metadata1           0x00080000      0x00100000      0
 3: metadata2           0x00080000      0x00180000      0
 4: fip-a               0x00300000      0x00200000      0
 5: fip-b               0x00300000      0x00500000      0
 6: UBI                 0x01900000      0x00800000      0
 7: UBI_2               0x0df00000      0x02100000      0

active partition: nand0,0 - (fsbl1) 0x00080000 @ 0x00000000

defaults:
mtdids  : nand0=nand0
mtdparts: mtdparts=nand0:512k(fsbl1),512k(fsbl2),512k(metadata1),512k(metadata2),3m(fip-a),3m(fip-b),25m(UBI),-(UBI_2)

Run the ubivolscript script to erase the system partitions and re-generate the UBI volumes:
```
=> run ubivolscript
```
The new partition table and UBI volumes are ready. Use the update command to program the firmware images into the linux and rootfs UBI volumes as usual,