This device has two sets of volumes: main ones (`kernel`, `rootfs`, etc) and
'backup' (`kernel.b`, `rootfs.b`, etc). Bootloader tries to determine which set of
volumes to use by looking at contens of `extra-para` and `extra-para.b` volumes.
These volumes contain JSON that looks like this:
```
{
"dbootFlag": "1",
"integerFlag": "1",
"fwFlag": "GOOD",
"score":1
}
```
It looks like the bootloader looks for `"fwFlag": "GOOD"` (as opposed to `BAD`)
then it compares `score` field - whichever 'good' volume has bigger score wins.
This determines which set of volumes to use to boot.
So for example if `extra-para` is good and has bigger score then `kernel`,
`rootfs`, etc volumes are used. This means bootloader needs to explain to the
kernel which volume to use for the rootfs. After looking at bootloader code with
disassembler I think it contains a bug. Relevant part of code looks something
like this:
```
if (image_id == 0) {
rootfs_volume_id = 8;
rootfs_volume_name = "rootfs";
}
else {
rootfs_volume_id = 0xf;
rootfs_volume_name = "rootfs.b";
}
sprintf(
&buffer,
0x800,
"console=ttyS0,115200 noinitrd ubi.mtd=3,2048 ubi.block=0,%s
root=/dev/ubiblock0_%d DKMGT_IMAGE_ID=%d DKMGT_IMAGE_TYPE=ubi",
rootfs_volume_name,
rootfs_volume_id,
image_id
);
```
Where `image_id == 0` if 'normal' (not '*.b' set of volumes is used).
However from device dumps we know that from the factory `rootfs.b` has id 8 and
`rootfs` has id 15.
So from above we can see that ids and names of rootfs volumes do not match. More
over - they are hardcoded in the bootloader.
Both things are problematic for OpwnWRT which completely removes volumes on
update meaning that volume ids may actually change.
So instead of relying on bootloader to provide the kernel with root device this
patch forces kernel to determine root automatically - and it defaults to
`rootfs` volume which is correct for our purposes.
Overall this makes image boot fine from flash after sysupgrade from inirams.
assuming `extra-para*` volumes make bootloader use non-'*.b' set of volumes.
Signed-off-by: Nikolay Martynov <mar.kolya@gmail.com>
This is a MT7621-based device with 128MB NAND flash, 256MB RAM, and a USB port.
The board has headers to attach console. In order for them to work two solder
bridges near those pads need to be made.
The defice has the following partition table:
```
0x000000000000-0x000000080000 : "u-boot"
0x000000080000-0x000000100000 : "u-boot-env"
0x000000100000-0x000000140000 : "factory"
0x000000140000-0x000007e00000 : "firmware"
0x000007e00000-0x000008000000 : "panic-ops"
```
`firmware` partition contains UBI volumes. Unfortunately I accidentally wiped
partition and I no longer have access to it.
`firmware` partition contains 'secondary' U-Boot which is run by 'first' u-boot.
It also contains various configuration partitions that include device info and
MAC address. There also seems to be 'primary' and 'backup' set of 'main' volumes.
U-boot has `mtkupgrade` command that just overrides data on firmware partitions.
Firmware file provided by TP-Link cannot be used with that command.
U-boot also has 'recovery' http server. Unfortunately I was not able to make it
work with manufacturer's firmware.
Manufacturer's firmware essentially contains multiple UBI volumes along with
'partition table'. Unfortunately I no longer can properly run manufacturer's
firmware so I cannot at the moment try to a support for building 'factory' images.
This patch adds support for initramfs image as well as sysupgrade image.
This seems to be pretty standard MT7621 board otherwise.
Things that work:
* network
* leds
* usb
* factory MAC detection
Signed-off-by: Nikolay Martynov <mar.kolya@gmail.com>
