linux-kernel - Re: [PATCH v1] mtd: spi-nor: unset quad

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Date:   Wed, 20 Jul 2022 15:48:41 +0200
From:   Michael Walle <michael@...le.cc>
To:     Tudor.Ambarus@...rochip.com
Cc:     p.yadav@...com, miquel.raynal@...tlin.com, richard@....at,
        vigneshr@...com, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org, heiko.thiery@...il.com
Subject: Re: [PATCH v1] mtd: spi-nor: unset quad_enable if SFDP doesn't
 specify it

Am 2022-07-19 06:57, schrieb Tudor.Ambarus@...rochip.com:
> On 3/4/22 20:51, Michael Walle wrote:
> 
> Hi!
> 
>> While the first version of JESD216 specify the opcode for 4 bit I/O
>> accesses, it lacks information on how to actually enable this mode.
>> 
>> For now, the one set in spi_nor_init_default_params() will be used.
>> But this one is likely wrong for some flashes, in particular the
>> Macronix MX25L12835F. Thus we need to clear the enable method when
>> parsing the SFDP. Flashes with such an SFDP revision will have to use 
>> a
>> flash (and SFDP revision) specific fixup.
> 
> This is equivalent to clearing the default QE method for all those 
> flashes
> that support SFDP, with implications for those that support SFDP Rev A.
> If I continue the logic, I could remove the default QE method from
> spi_nor_init_default_params(), but I don't think I would like that.
> You could use a post_bfpt hook without explicitly clearing it here.
> 
> Would you please explain more why is clearing the default method better
> than using a wrong default one, and why you chose to do this just for
> the Rev A SFDP flashes and you didn't include the no-SFDP flashes as 
> well?

Honestly, I don't care too much about this flash. I can't remember
any details from this 4 months old thread. Sorry. I guess it is
fine to drop this patch. If someone cares, she or he can
resurrect this one.

-michael