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

From: Ahmad Fatoum <a.fatoum@pengutronix.de>
To: Tokunori Ikegami <ikegami.t@gmail.com>,
	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
Subject: Re: [BUG] mtd: cfi_cmdset_0002: write regression since v4.17-rc1
Date: Mon, 14 Feb 2022 17:22:34 +0100	[thread overview]
Message-ID: <579eab10-594c-d6b2-0ddb-ea6ab8e02856@pengutronix.de> (raw)
In-Reply-To: <66ee55d9-4f20-6722-6097-e53c2108ea07@gmail.com>

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>

>>>> 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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