HomeHub 5A: Clean NAND Flash and Custom Flash Layout


#1

I have a HomeHub 5A and I mistakenly erased the whole NAND Flash. As I understand it had some Volumes/Partitions that I dont remember. I dont have a copy of the flash layout either and cant find one in wiki or on the internet. I have a separate router so in case HH doesnt wake up anymore I can live with that. But I see this as an opportunity to learn something and try to revive it as far as I can go.

  1. So the first question, to developers here, is that if I create a custom flash layout will it work?
    I have already read the wiki and found some interesting information about flash layouts. So I understand that I need a U-boot partition to basically turn on the router and then it needs to load data from some other partition (which I dont know). It also needs some calibration data for Wi-Fi to work but I dont have it yet (maybe someone else can provide it?).

  2. What kind of U-boot would I need? Can I just pick one from Openwrt downloads? Or do I need a custom U-boot from someone else?
    Maybe this one? This U-boot is quite big, more than 10 MBs, but it should not be a problem since we have 128 MBs of flash available. But I would still like to know any pros and cons.

  3. I can basically turn on this router through CFG 04 prompt and load a ram-uboot-image and then tftpboot the install image and it pretty much works. But it doesnt change anything since there are no partitions defined. Also I found in the U-boot that HH5A has a UBI filesystem so the default partition is just a ubi at 0. Furthermore it needs volumes to define how to store various data, like U-boot, kernel, rootfs etc. I think mtd command should be the way to go but I am not sure because ubi commands are also available. So I need a little help here determining what to do.

Lastly, I would probably need the dump data from those partitions/volumes from some other HH5A but I am not sure if that would work properly. If someone has a HH5A lying around can you please dump the partitions and upload somewhere? That would be really helpful but I am also open to any other suggestions. I do have the backup of mtd4 which is around 126 or 127 MBs maybe.

So please take a look here and help me to understand how to proceed further. Thank you.


#2

Within the install system, run restore with your mtd4 dump.
If it succeeds, you can then redo the OpenWrt installation.


#3

Alright but as I said, I erased the NAND flash and there are no partitions in it now. No U-boot, kernel, calibration data or anything. Will it still succeed?

While looking at the serial output I see that the install-image creates 5 mtd partitions within the ram image. Can I use this flash table layout for the HH5A and write it to the router through U-boot? The flash table is as:

Creating 5 MTD partitions on "14000000.nand-parts":
[   10.295773] 0x000000000000-0x0000000a0000 : "u-boot"
[   10.385882] 0x0000000a0000-0x0000000c0000 : "uboot-env"
[   10.487943] 0x0000000c0000-0x000000100000 : "unused"
[   10.589382] 0x000000100000-0x000007f80000 : "ubi"
[   10.722801] 0x000000000000-0x000008000000 : "nand_chip"

#4

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