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Message-ID: <117facba-ba33-349d-1085-25315cc1ae92@gmail.com>
Date:   Sun, 20 Feb 2022 21:22:35 +0900
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Subject: Re: [BUG] mtd: cfi_cmdset_0002: write regression since v4.17-rc1
Content-Language: en-US
From:   Tokunori Ikegami <ikegami.t@gmail.com>
To:     Ahmad Fatoum <a.fatoum@pengutronix.de>,
        Thorsten Leemhuis <regressions@leemhuis.info>,
        linux-mtd@lists.infradead.org, Joakim.Tjernlund@infinera.com,
        miquel.raynal@bootlin.com, vigneshr@ti.com, richard@nod.at,
        "regressions@lists.linux.dev" <regressions@lists.linux.dev>
Cc:     Chris Packham <chris.packham@alliedtelesis.co.nz>,
        Brian Norris <computersforpeace@gmail.com>,
        David Woodhouse <dwmw2@infradead.org>, marek.vasut@gmail.com,
        cyrille.pitchen@wedev4u.fr,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        linuxppc-dev@lists.ozlabs.org
References: <b687c259-6413-26c9-d4c9-b3afa69ea124@pengutronix.de>
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 <e11b76dc-5539-fb7e-da1c-a5005713d6b0@gmail.com>
 <3dbbcee5-81fc-cdf5-9f8b-b6ccb95beddc@pengutronix.de>
 <0f2cfcac-83ca-51a9-f92c-ff6495dca1d7@gmail.com>
 <b231b498-c8d2-28af-ce66-db8c168047f7@pengutronix.de>
 <66ee55d9-4f20-6722-6097-e53c2108ea07@gmail.com>
 <579eab10-594c-d6b2-0ddb-ea6ab8e02856@pengutronix.de>
 <cedb1604-e024-2738-5b33-15703a653803@gmail.com>
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Hi Ahmad-san,

Could you please try the version 2 patch attached for the error case?
This version is to check the DQ true data 0xFF by chip_good().
But I am not sure if this works or not since the error is possible to be 
caused by Hi-Z 0xff on floating bus or etc.

On 2022/02/15 3:46, Tokunori Ikegami wrote:
> Hi Ahmad-san,
>
> On 2022/02/15 1:22, Ahmad Fatoum wrote:
>> Hello Tokunori-san,
>>
>> On 13.02.22 17:47, Tokunori Ikegami wrote:
>>> Hi Ahmad-san,
>>>
>>> Thanks for your confirmations. Sorry for late to reply.
>> No worries. I appreciate you taking the time.
>>
>>> Could you please try the patch attached to disable the chip_good() 
>>> change as before?
>>> I think this should work for S29GL964N since the chip_ready() is 
>>> used and works as mentioned.
>> yes, this resolves my issue:
>> Tested-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> Thanks for your testing. I have just sent the patch to review.
>>
>>>>>> Doesn't seem to be a buffered write issue here though as the writes
>>>>>> did work fine before dfeae1073583. Any other ideas?
>>>>> At first I thought the issue is possible to be resolved by using 
>>>>> the word write instead of the buffered writes.
>>>>> Now I am thinking to disable the changes dfeae1073583 partially 
>>>>> with any condition if possible.
>>>> What seems to work for me is checking if chip_good or chip_ready
>>>> and map_word is equal to 0xFF. I can't justify why this is ok though.
>>>> (Worst case bus is floating at this point of time and Hi-Z is read
>>>> as 0xff on CPU data lines...)
>>> Sorry I am not sure about this.
>>> I thought the chip_ready() itself is correct as implemented as the 
>>> data sheet in the past.
>>> But it did not work correctly so changed to use chip_good() instead 
>>> as it is also correct.
>> What exactly in the datasheet makes you believe chip_good is not 
>> appropriate?
> I just mentioned about the actual issue behaviors as not worked 
> chip_good() on S29GL964N and not worked chip_ready() on 
> MX29GL512FHT2I-11G before etc.
> Anyway let me recheck the data sheet details as just checked it again 
> quickly but needed more investigation to understand.

As far as I checked still both chip_good() and chip_ready() seem correct 
but still the root cause is unknown.
If as you mentioned the issue was cased by the DQ true data 0xFF I am 
not sure why the read work without any error after the write operation.
Also if the error was caused by the Hi-Z 0xff on floating bus as 
mentioned I am not sure why the read work without any error after the 
write operation with chip_ready().
Sorry anyway the root cause is also unknown when the write operation was 
changed to use chip_good() instead of chip_ready().

Regards,
Ikegami

>
> Regards,
> Ikegami
>
>>
>> Cheers,
>> Ahmad
>>
>>
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