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From:   "Bean Huo (beanhuo)" <beanhuo@micron.com>
To:     Boris Brezillon <boris.brezillon@bootlin.com>,
        Chris Packham <chris.packham@alliedtelesis.co.nz>
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        "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>
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: AdQXnRLnAy8+kBX/RY20g+cq7ZFQJQ==
Date:   Mon, 9 Jul 2018 15:54:11 +0000
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Hi, Boris and Chris

>>
>> 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.

MT29F1G08ABAFAWP-ITE:F is Micron 70s SLC NAND with on-die ECC.
If the bit7 in the byte 5 of READID default is 1(ECC Enabled), it is true on-die ECC
Cannot be disabled by SET Feature command.
In case sending Set Feature command, you can check previous command is success or not by
Get Feature or check this bit7 in byte 5 of READID later.

To check if this device supports on-die ECC or not, you can use inter ECC level (bit 0 and bit1 in byte 5 of READID)  
http://lists.infradead.org/pipermail/linux-mtd/2017-April/073370.html

//beanhuo