NAND flashes in Broadcom routers: bad blocks, ECC

[Rafał Miłecki]

On 19 August 2014 20:45, Rafał Miłecki <zajec5 at gmail.com> wrote:
> I wanted to finally switch from NAND_ECC_NONE to NAND_ECC_SOFT (there
> is no hw ECC) but it appears it won't be that straightforward. The
> problem is NAND implementation in Broadcom's CFE bootloader.
>
> It appears that all the bootloader cares about is if block is good or
> bad. I think it doesn't even use BBT. It simply checks for oob[0x0]
> (or oob[0x5] for small flashes) being 0xff. Then it writes to the
> block or skips it. The bootloader doesn't seem to even calculate ECC
> when writing! So after installing firmware using bootloader all OOB
> content is 0xFF. Of course enableing NAND_ECC_SOFT results in
> uncorrectable errors:
> bcm47xxnflash: NAND_CMD_RNDOUT len:0x0F
> bcm47xxnflash: NAND_CMD_RNDOUT data FF FF FF FF FF FF FF FF FF FF FF
> FF FF FF FF FF
> __nand_correct_data: uncorrectable ECC error
> __nand_correct_data: uncorrectable ECC error
> __nand_correct_data: uncorrectable ECC error
> mtd_read error while reading (offset: 0x60000)!
>
> So I wonder how we could deal with that. Should I somehow detect if
> this is first boot after installation and calculate ECCs on my own?
> Hoping nothing wrong will happen of the first read?

Any ideas?