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

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Date:   Tue, 24 Jul 2018 08:23:27 +1000
From:   NeilBrown <neil@...wn.name>
To:     Brian Norris <computersforpeace@...il.com>
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.

On Mon, Jul 23 2018, Brian Norris wrote:

> 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/

Thanks for the links.

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

No need (though I wouldn't object).  Thanks for the heads-up!

>
> 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.
>
I'm strongly against degrading experience - partly because it could be
my experiences, partly because it seems to go against the pragmatic
basis of Linux - we build this thing because it is useful.
I don't object to highly focuses handling of specific "quirks" - that
seems to be an established pattern in Linux.

Thanks,
NeilBrown

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