Re: [ANNOUNCE] MLC support for UBI/UBIFS

[Boris Brezillon <boris.brezillon@free-electrons.com>]

On Wed, 4 May 2016 08:55:12 +0000
Bean Huo 霍斌斌 (beanhuo) <beanhuo@micron.com> wrote:

> Hi, Richard
> Yes , different with "dis6 and dis3", but I think this is not a perfect 
> Solution on paired-page distance detect. Because different vendor and different series NAND with different such paired-page distance function. as a result, this table will be bigger and bigger. I now want to do if we can probe this information from DTS.

Sorry but I'm clearly opposed to that: the NAND infrastructure provides
a way to uniquely identify the part number, let's not add extra
information in the DT if it's not needed.
Just giving a simple use case where putting NAND chip details in the DT
is a bad idea: some board manufacturers choose 2 or 3 equivalent NANDs
coming from different vendors (and those NANDs may have different
pairing scheme). With your solution this means having one DT per NAND
chip, which is not easy to deal with.

For the "the table will keep growing and become unmaintainable"
argument, I agree. My plan is to provide a per-vendor ->init() hook
so that each vendor can implement a simpler solution to detect/assign
the pairing scheme (I'm pretty sure this is correlated to the NAND
technology...), or other vendor specific stuff (read-retry, HW SLC
mode, ...).

Regarding your initial statement, are you sure your NAND chip does not
use one of the already defined scheme. I had a look at several NAND
datasheets (including Micron ones), and all of them were using either
distance 3 or distance 6.
Can you share more information about those different pairing scheme?

Thanks,

Boris


-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com