Re: spi-nor: maxronix MX25L12835F support

From: Pratyush Yadav <p.yadav@ti.com>
To: Michael Walle <michael@walle.cc>
Cc: Heiko Thiery <heiko.thiery@gmail.com>, linux-mtd@lists.infradead.org
Subject: Re: spi-nor: maxronix MX25L12835F support
Date: Tue, 16 Feb 2021 15:46:05 +0530	[thread overview]
Message-ID: <20210216101603.s22b2fs7en52ximf@ti.com> (raw)
In-Reply-To: <d7e81d38064ba59a24ec243cb84a1d97@walle.cc>

On 16/02/21 10:48AM, Michael Walle wrote:
> Am 2021-02-16 10:27, schrieb Pratyush Yadav:
> > On 15/02/21 10:53PM, Heiko Thiery wrote:
> > > Hi all,
> > > 
> > > I faced an issue with a SPI flash on our board. We use a macronix
> > > MX25L12835F [1]. Unfortunately this flash has the same JEDEC ID like
> > > the MX25L12805D [2].
> > > 
> > > The newer MX25L12835F has support for dual/quad read mode and RDSFDP
> > > while the older doesn't.
> > > 
> > > I thought that I could do a fixup with a device specific
> > > post_bfpt_fixups() call but by now this seems not possible. The older
> > > MX25L12805D has no flags set that allows a call to
> > > spi_nor_sfdp_init_params() and implements the fixup.
> > > 
> > > Has anyone an idea how to solve this?
> > 
> > The post_sfdp fixup is always run regardless of whether the flash has
> > SFDP or not. You can try putting your flash-specific fixups there.
> 
> Well the problem here is, that the SFDP setup is skipped though the
> flash would support SFDP. If the jedec id wasn't already in the table,
> there would be the flag SPI_NOR_QUAD_READ and the SFDP would be
> parsed. But because there is already the legacy device (which likely
> doesn't support SFDP) it really doesn't fit.

Is it possible to differentiate between the two flashes in any way? If 
so you can use the init_params() fixup to check that add the flags for 
the new flash. Modifying nor->info feels kind of wrong but it is an 
acceptable compromise in this situation IMO.

> 
> Its unclear to me, why the SFDP is only parsed if one of the
> SPI_NOR_*_READ flags are set.

I don't know either. Probably to differentiate between legacy flashes 
that don't support SFDP at all.

> 
> > > [1] https://www.macronix.com/Lists/Datasheet/Attachments/7397/MX25L12835F,%203V,%20128Mb,%20v1.6.pdf
> > > [2] https://www.mxic.com.tw/Lists/Datasheet/Attachments/7321/MX25L12805D,%203V,%20128Mb,%20v1.2.pdf
> > 
> > Both these links are broken.
> 
> mh, they work for me.

Ah yes they do. My terminal emulator didn't parse them correctly and 
opened something different in the browser.

-- 
Regards,
Pratyush Yadav
Texas Instruments Inc.

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