linux-kernel - Re: [PATCH v6 0/6] mtd: rawnand: support MT29F1G08ABAFAWP-ITE:F

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Date:   Sun, 8 Jul 2018 23:56:52 +0000
From:   Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To:     Boris Brezillon <boris.brezillon@...tlin.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "miquel.raynal@...tlin.com" <miquel.raynal@...tlin.com>,
        "computersforpeace@...il.com" <computersforpeace@...il.com>,
        "dwmw2@...radead.org" <dwmw2@...radead.org>,
        "Bean Huo (beanhuo)" <beanhuo@...ron.com>
Subject: Re: [PATCH v6 0/6] mtd: rawnand: support MT29F1G08ABAFAWP-ITE:F

Hi Boris,

On 07/07/18 09:37, Boris Brezillon wrote:
> On Fri, 6 Jul 2018 21:27:20 +0200
> Boris Brezillon <boris.brezillon@...tlin.com> wrote:
> 
>> On Mon, 25 Jun 2018 10:44:42 +1200
>> Chris Packham <chris.packham@...iedtelesis.co.nz> wrote:
>>
>>> Hi,
>>>
>>> I'm looking at adding support for the Micron MT29F1G08ABAFAWP-ITE:F chip
>>
>> Hm, it's even worse than I thought. The model name does not include the
>> -ITE suffix (E means ECC can't be disabled), which means we have no way
>> to detect the version with forced on-die ECC.
>>
>> I see 2 solutions to this problem:
>> 1/ Bean provides us a solution to reliably detect when ECC can be
>>     de-actived and when it can't
>> 2/ We only ever expose 64 bytes of OOB to the user and consider that
>>     ECC can be disabled, even if it can't in reality
>>
> 
> After reading the doc again, I forgot one thing you can try before
> deciding to go for option #2.
> 
> 8th bit in byte 5 of READID's result encodes whether the on-die ECC
> state (enabled or not). I remember we had a discussion with Bean where
> he told us this was a runtime status reflecting the on-die ECC state,
> which is crazy, since READID might return different values depending on
> the NAND state, and most of the code in the core assumes READID
> provides a fixed ID that encodes the chip characteristics/capabilities,
> not its state.
> 
> Anyway, if this bit is actually reflecting the on-die ECC state and
> on-die cannot be disabled on your chip, it should stay at 1 even after
> you have sent the SET_FEATURES(DISABLE_ECC) command. Let's hope this
> works as I expect, otherwise we're back to option #2 until Bean suggest
> something else.
> 

I'm away from work this week so I don't have access to that system. But 
I can take a look when I get back. From memory though there was very 
little that you could tell from the id/params on this chip (FYI we've 
decided to use a chip from a different vendor for production).