[OpenWrt-Devel] [PATCH] kernel: tolerate using UBI/UBIFS on MLC flash (FS#1830)
koen.vandeputte at ncentric.com
Mon Oct 22 09:48:29 EDT 2018
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. 
>> According to David Oberhollenzer :
>> 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>
>>  https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v4.14.77&id=577b4eb23811dfc8e38924dc476dbc866be74253
>>  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.
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 ..
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