[OpenWrt-Devel] [PATCH] kernel: tolerate using UBI/UBIFS on MLC flash (FS#1830)

[Koen Vandeputte]

On 23.10.18 17:43, Christian Lamparter wrote:
> Sorry, hit "Send" by accident
>
> On Tuesday, October 23, 2018 2:37:16 PM CEST Koen Vandeputte wrote:
>> On 22.10.18 19:27, Christian Lamparter wrote:
>>> On Monday, October 22, 2018 3:48:29 PM CEST Koen Vandeputte wrote:
>>>> On 20.10.18 17:46, Hauke Mehrtens wrote:
>>>>> On 10/18/2018 02:28 PM, Koen Vandeputte wrote:
>>>>>> starting from upstream commit 577b4eb23811 ("ubi: Reject MLC NAND")
>>>>>> it is not allowed to use UBI and UBIFS on a MLC flavoured NAND flash chip. [1]
>>>>>>
>>>>>> According to David Oberhollenzer [2]:
>>>>>>
>>>>>> The real problem is that on MLC NAND, pages come in pairs.
>>>>>>
>>>>>> Multiple voltage levels inside a single, physical memory cell are used to
>>>>>> encode more than one bit. Instead of just having pages that are twice as big,
>>>>>> the flash exposes them as *two different pages*. Those pages are usually not
>>>>>> ordered sequentially either, but according to a vendor/device specific
>>>>>> pairing scheme.
>>>>>>
>>>>>> Within OpenWrt, devices utilizing this type of flash,
>>>>>> combined with ubi(fs) will be bricked when a user upgrades
>>>>>> from 17.01.4 to a newer version as the MLC will be refused.
>>>>>>
>>>>>> As these devices are currently advertised as supported by OpenWrt,
>>>>>> we should at least maintain the original state during the lifecycle
>>>>>> of the current releases.
>>>>>>
>>>>>> Support can be gracefully ended when a new release-branch is created.
>>>>>>
>>>>>> Signed-off-by: Koen Vandeputte <koen.vandeputte at ncentric.com>
>>>>>>
>>>>>> [1] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v4.14.77&id=577b4eb23811dfc8e38924dc476dbc866be74253
>>>>>> [2] https://lore.kernel.org/patchwork/patch/920344/
>>>>>> ---
>>>>>>
>>>>>> Mainly intended for discussion first on this approach before applying it.
>>>>>> Can be cherrypicked to 18.06.
>>>>>>
>>>>>> Feel free to drop your (n)ack on this approach
>>>>> Have you checked if these are really MLC chips or if they are just
>>>>> getting detected wrongly?
>>>>> I think I saw some SPI NAND chips which a patched Linux detected as MLC
>>>>> but the datasheet said they are SLC chips.
>>>>>
>>>>> Hauke
>>>> Very good point.
>>>> I've requested Mikrotik this morning to provide some details about the
>>>> actual chips being used since the launch of that board ..
>>> For the RB450/G you can take a look at the User Guide on their side:
>>> <https://mikrotik.com/product/RB450G#fndtn-downloads>
>>> <https://i.mt.lv/cdn/rb_files/rb450GugA.pdf>
>>>
>>> On Page 3 there's a "System Board View" with a bottom view of the PCB
>>> and this is where the NAND chip is located. It reads:
>>>
>>> HY27UT084G2A
>>>
>>> This translates to:
>>> <http://natisbad.org/NAS/refs/Hynix_NAND_flash_part_number_decoding.pdf>
>>>
>>> HY27UT084G2A
>>>     ||||
>>>     |||^--- T = MLC + Single Die + Large Block
>>>     ||^---U = 2.7V~3.6V
>>>     |^---7 = NAND FLASH
>>>     ^---2 = FLASH
>>>    
>>> So, it is NAND MLC FLASH.
>>>
>> Received a reply from Mikrotik tech dept.:
>>
>>
>> Hello,
>>
>> Mainly there are two possible NAND chips for RB450G:
>> W29N04GVSIAA (see attachment);
>> MT29F4G08ABADAWPD.
>>
>> Can you provide some device serial numbers?
>>
>>
>> Best regards,
>> Elans L.
>>
>>
>>
>>
>> Checking the datasheets from both chips mentioned above shows they are both SLC flash.
>> @Christian, do you have this board?  Could you provide the serial?
> No, luckily it isn't one of mine. But Mikrotik want to dig: I do have a serial number
> of an affected board: 1DFC018EF642.

Just got a reply back from Mikrotik.

It seems this serial is not correct?

> I found it on the OpenWrt's Device wiki:
> <https://openwrt.org/toh/mikrotik/rb450g?s[]=rb450g#photos>
>
> And interestingly enough, there's also a different list of
> supported flash chips there:
> Hynix NAND 512MiB 3,3V 8-bit (HY27UF082G2A, HY27UT084G2A) or Samsung 4Gibit (K9F4G08U0B-PIB0
>
> Regards,
> Christian
>   
>
>

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