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From:   Chris Packham <Chris.Packham@alliedtelesis.co.nz>
To:     Boris Brezillon <boris.brezillon@bootlin.com>
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>,
        "miquel.raynal@bootlin.com" <miquel.raynal@bootlin.com>,
        "computersforpeace@gmail.com" <computersforpeace@gmail.com>,
        "dwmw2@infradead.org" <dwmw2@infradead.org>,
        "Bean Huo (beanhuo)" <beanhuo@micron.com>
Subject: Re: [PATCH v6 0/6] mtd: rawnand: support MT29F1G08ABAFAWP-ITE:F
Thread-Topic: [PATCH v6 0/6] mtd: rawnand: support MT29F1G08ABAFAWP-ITE:F
Thread-Index: AQHUDAz7Ft0gL2AzJEuev8VL5BoQ1g==
Date:   Sun, 8 Jul 2018 23:56:52 +0000
Message-ID: <da6f03d541e24e008f84f6f18fc8e77a@svr-chch-ex1.atlnz.lc>
References: <20180624224448.21872-1-chris.packham@alliedtelesis.co.nz>
 <20180706212720.0e9dacb8@bbrezillon> <20180706233701.05da0666@bbrezillon>
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Hi Boris,=0A=
=0A=
On 07/07/18 09:37, Boris Brezillon wrote:=0A=
> On Fri, 6 Jul 2018 21:27:20 +0200=0A=
> Boris Brezillon <boris.brezillon@bootlin.com> wrote:=0A=
> =0A=
>> On Mon, 25 Jun 2018 10:44:42 +1200=0A=
>> Chris Packham <chris.packham@alliedtelesis.co.nz> wrote:=0A=
>>=0A=
>>> Hi,=0A=
>>>=0A=
>>> I'm looking at adding support for the Micron MT29F1G08ABAFAWP-ITE:F chi=
p=0A=
>>=0A=
>> Hm, it's even worse than I thought. The model name does not include the=
=0A=
>> -ITE suffix (E means ECC can't be disabled), which means we have no way=
=0A=
>> to detect the version with forced on-die ECC.=0A=
>>=0A=
>> I see 2 solutions to this problem:=0A=
>> 1/ Bean provides us a solution to reliably detect when ECC can be=0A=
>>     de-actived and when it can't=0A=
>> 2/ We only ever expose 64 bytes of OOB to the user and consider that=0A=
>>     ECC can be disabled, even if it can't in reality=0A=
>>=0A=
> =0A=
> After reading the doc again, I forgot one thing you can try before=0A=
> deciding to go for option #2.=0A=
> =0A=
> 8th bit in byte 5 of READID's result encodes whether the on-die ECC=0A=
> state (enabled or not). I remember we had a discussion with Bean where=0A=
> he told us this was a runtime status reflecting the on-die ECC state,=0A=
> which is crazy, since READID might return different values depending on=
=0A=
> the NAND state, and most of the code in the core assumes READID=0A=
> provides a fixed ID that encodes the chip characteristics/capabilities,=
=0A=
> not its state.=0A=
> =0A=
> Anyway, if this bit is actually reflecting the on-die ECC state and=0A=
> on-die cannot be disabled on your chip, it should stay at 1 even after=0A=
> you have sent the SET_FEATURES(DISABLE_ECC) command. Let's hope this=0A=
> works as I expect, otherwise we're back to option #2 until Bean suggest=
=0A=
> something else.=0A=
> =0A=
=0A=
I'm away from work this week so I don't have access to that system. But =0A=
I can take a look when I get back. From memory though there was very =0A=
little that you could tell from the id/params on this chip (FYI we've =0A=
decided to use a chip from a different vendor for production).=0A=