linux-kernel - Re: [PATCH v2 1/3] mtd: spi-nor: macronix: Drop the redundant flash info fields

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Message-ID: <cfde5583-fcc1-4c08-9893-5a09a148b475@roeck-us.net>
Date: Tue, 30 Sep 2025 07:39:55 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Pratyush Yadav <pratyush@...nel.org>,
 Cheng Ming Lin <linchengming884@...il.com>
Cc: Michael Walle <mwalle@...nel.org>,
 Tudor Ambarus <tudor.ambarus@...aro.org>,
 Cheng Ming Lin <chengminglin@...c.com.tw>, miquel.raynal@...tlin.com,
 richard@....at, vigneshr@...com, linux-mtd@...ts.infradead.org,
 linux-kernel@...r.kernel.org, alvinzhou@...c.com.tw, leoyu@...c.com.tw,
 Maarten Zanders <maarten@...ders.be>
Subject: Re: [PATCH v2 1/3] mtd: spi-nor: macronix: Drop the redundant flash
 info fields

On 9/30/25 05:19, Pratyush Yadav wrote:
> On Tue, Sep 30 2025, Cheng Ming Lin wrote:
> 
>> Hi Michael,
>>
>> Michael Walle <mwalle@...nel.org> 於 2025年9月24日 週三 下午8:11寫道：
>>>
>>>> The root cause of this problem lies in the failure of parsing the SFDP
>>>> data for the flash, rather than an issue with the patch itself. I believe
>>>> we should not revert this patch.
>>>
>>> I disagree. There are Macronix flashes with that ID which doesn't
>>> have SFDP.  And this patch is dropping support for them. See also
>>> [1]. Now I'm not sure it is worth reverting this commit. Nobody,
>>> except Guenter complained, but only *so far* (and that patch is in
>>> since 6.16). Any opinions?
> 
> When I read this I was just hoping no one complains and we end up just
> dropping support for these flashes that no one seems to use...
> 
>>
>> I agree with reverting this patch. When I initially verified it, the
>> devices I had on hand all supported SFDP, so I did not catch this issue.
>> After checking again, I confirm that some older flashes without SFDP are
>> indeed affected.
> 
> Do you know if these flashes are used in any devices that are actively
> used and maintained? If so, we should revert. If it is likely they
> aren't actively used, then maybe we just keep things as they are?
> Dunno...
> 

qemu emulates the chips, meaning the qemu emulations using them no longer work.
This is how I found the problem.

I carry a downstream qemu change to instantiate different flash types on the
affected boards, so this is no longer a problem for me. In case anyone wonders
if/why I didn't submit that into qemu - I did. It was was rejected.

Guenter

>>
>> Would it make sense to only change the `.name` field to use a comment,
>> while keeping the rest as is? That way we can still support flashes that
>> may not provide SFDP.
> 
> Sure, that would be a good improvement over a plain revert. Maybe as a
> follow up patch to the revert?
>