linux-kernel - Re: [PATCH] mtd: spi-nor: clear Extended Address Reg on switch to 3-byte addressing.

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Message-ID: <CAN8TOE-+XpeQ0eLEW3YdAGGtuw5reeuJRZvnMb+QquJycJWLQA@mail.gmail.com>
Date:   Mon, 23 Jul 2018 15:17:11 -0700
From:   Brian Norris <computersforpeace@...il.com>
To:     NeilBrown <neil@...wn.name>
Cc:     Marek Vasut <marek.vasut@...il.com>,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        David Woodhouse <dwmw2@...radead.org>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Richard Weinberger <richard@....at>,
        linux-mtd@...ts.infradead.org,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        Hou Zhiqiang <Zhiqiang.Hou@....com>
Subject: Re: [PATCH] mtd: spi-nor: clear Extended Address Reg on switch to
 3-byte addressing.

Hi Neil,

On Mon, Jul 23, 2018 at 2:45 PM, NeilBrown <neil@...wn.name> wrote:
> On Mon, Jul 23 2018, Brian Norris wrote:
>> On Mon, Apr 9, 2018 at 6:05 PM, NeilBrown <neil@...wn.name> wrote:
>>> On Mon, Apr 09 2018, Marek Vasut wrote:
>>>> On 04/08/2018 11:56 PM, NeilBrown wrote:
>>>>> were added to Linux.  They appear to be designed to address a very
>>>>> similar situation to mine.  Unfortunately they aren't complete as the
>>>>> code to disable 4-byte addressing doesn't follow documented requirements
>>>>> (at least for winbond) and doesn't work as intended (at least in one
>>>>> case - mine). This code should either be fixed (e.g. with my patch), or removed.
>>
>> I would (and already did) vote for removal. The shutdown() hook just
>> papers over bugs and leads people to think that it is a good solution.
>> There's a reason we rejected such patches repeatedly in the past. This
>> one slipped through.
>
> Hi Brian,
>  thanks for your thoughts.
>  Could you just clarify what you see as the end-game.
>  Do you have an alternate approach which can provide reliability for the
>  various hardware which currently seems to need these patches?
>  Or do you propose that people with this hardware should suffer
>  a measurably lower level of reliability than they currently enjoy?

I'd suggest following the original thread, which I resurrected:

[PATCHv3 2/2] mtd: m25p80: restore the status of SPI flash when exiting
https://lkml.org/lkml/2018/7/23/1207
https://patchwork.ozlabs.org/patch/845022/

I suppose I could CC you on future replies...

My current summary: I'd prefer the hack be much more narrowly applied,
with a big warning, if we apply it at all. But if we don't merge
something to narrow the use of the hack, then yes, I'd prefer a
degraded experience for crappy products over today's status quo.

Brian