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

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: linuxppc-dev@lists.ozlabs.org,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	marek.vasut@gmail.com,
	Chris Packham <chris.packham@alliedtelesis.co.nz>,
	Pengutronix Kernel Team <kernel@pengutronix.de>,
	cyrille.pitchen@wedev4u.fr,
	Brian Norris <computersforpeace@gmail.com>,
	David Woodhouse <dwmw2@infradead.org>
Subject: Re: [BUG] mtd: cfi_cmdset_0002: write regression since v4.17-rc1
Date: Tue, 15 Feb 2022 03:46:18 +0900	[thread overview]
Message-ID: <cedb1604-e024-2738-5b33-15703a653803@gmail.com> (raw)
In-Reply-To: <579eab10-594c-d6b2-0ddb-ea6ab8e02856@pengutronix.de>

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.

Regards,
Ikegami

>
> Cheers,
> Ahmad
>
>