Re: [PATCH v3 0/7] Marvell NAND controller rework with ->exec_op()

[Robert Jarzmik <robert.jarzmik@free.fr>]

Boris Brezillon <boris.brezillon@free-electrons.com> writes:

> On Fri, 12 Jan 2018 10:34:13 +0100
> Robert Jarzmik <robert.jarzmik@free.fr> wrote:
>
>> Boris Brezillon <boris.brezillon@free-electrons.com> writes:
> Because we though scanning of BBMs was working with the old pxa driver
> (which should be the case for your setup, BTW), and we thought the new
> driver was introducing a regression here.
That's what happens :
 - flash_bbt=1 with old driver => everything works fine
 - flash_bbt=1 with marvell_nand => BBT is damaged (or so I believe from
   Miquel's analysis)

> BTW, did you ever try with the old driver and ->flash_bbt = false? If
> you did not, can you test?
Sure, just did, same behavior as with marvell_nand :
 - bad erase blocks (almost) everywhere
 - ubifs error

>> I think we're still not aligned here. There are _no_ bad block markers in the
>> OOB on my flash, because there is a BBT at the end.
>
> That's not how it works. The BBT is a way to get information about bad
> blocks within a single read access, but, if you can preserve BBMs and
> keep them updated (which is the case here), you should do it, just in
> case you lose the BBT.
You're probably right today. But this assertion is probably wrong for system
created in early 2000s ... :)

>> > So, the symptoms we're seeing here, where almost all blocks are reported as
>> > bad when scanning BBMs, is not expected, and that's what we're trying to
>> > debug/fix.  
>> Well, I still think this is not something to fix ... I still think that OOB data
>> is not relevant as to the state of bad blocks in my flash ...
>
> Hm, I disagree. What if, for any reason, the BBT is lost? Don't you
> want the full scan to work?
If the BBT is lost, you have the mirror BBT, it's its purpose.

> Okay, so I have another solution for that: drop the NAND_BBT_CREATE and
> NAND_BBT_WRITE here [1] and here [2]. That should let you read the
> existing BBT without updating it or creating a new one if it's not
> detected.
Okay, let's try the marvell-nand-bug branch with this included.
It works :
[   18.302123] ubi0: attached mtd5 (name "root", size 37 MiB)
[   18.307691] ubi0: PEB size: 131072 bytes (128 KiB), LEB size: 126976 bytes
[   18.315003] ubi0: min./max. I/O unit sizes: 2048/2048, sub-page size 2048
[   18.322155] ubi0: VID header offset: 2048 (aligned 2048), data offset: 4096
[   18.329167] ubi0: good PEBs: 297, bad PEBs: 0, corrupted PEBs: 0
[   18.335789] ubi0: user volume: 1, internal volumes: 1, max. volumes count: 128
[   18.343409] ubi0: max/mean erase counter: 6/4, WL threshold: 4096, image sequence number: 30621
[   18.352460] ubi0: available PEBs: 0, total reserved PEBs: 297, PEBs reserved for bad PEB handling: 40
[   18.361937] ubi0: background thread "ubi_bgt0d" started, PID 411

That means the BBT reading is the issue don't you think ?

Now if I keep NAND_BBT_CREATE but remove NAND_BBT_WRITE same thing, it works as
well. That leaves only the re-enabling of the BBT write, which I'll do as soon
as you tell me my NAND won't be damaged.

Cheers.

-- 
Robert