linux-kernel - Re: [BUG] mtd: cfi_cmdset_0002: write regression since v4.17-rc1

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Message-ID: <579eab10-594c-d6b2-0ddb-ea6ab8e02856@pengutronix.de>
Date:   Mon, 14 Feb 2022 17:22:34 +0100
From:   Ahmad Fatoum <a.fatoum@...gutronix.de>
To:     Tokunori Ikegami <ikegami.t@...il.com>,
        Thorsten Leemhuis <regressions@...mhuis.info>,
        linux-mtd@...ts.infradead.org, Joakim.Tjernlund@...inera.com,
        miquel.raynal@...tlin.com, vigneshr@...com, richard@....at,
        "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>
Cc:     Chris Packham <chris.packham@...iedtelesis.co.nz>,
        Brian Norris <computersforpeace@...il.com>,
        David Woodhouse <dwmw2@...radead.org>, marek.vasut@...il.com,
        cyrille.pitchen@...ev4u.fr,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [BUG] mtd: cfi_cmdset_0002: write regression since v4.17-rc1

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@...gutronix.de>

>>>> 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?

Cheers,
Ahmad


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