linux-kernel - Re: [PATCH] mtd: spi-nor: mt25qu: Ignore 6th ID byte

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Message-ID: <85251c3b-13c1-8b24-0ce2-6793ea55e39a@nokia.com>
Date:   Tue, 23 Nov 2021 13:13:07 +0100
From:   Alexander Sverdlin <alexander.sverdlin@...ia.com>
To:     Michael Walle <michael@...le.cc>
Cc:     linux-mtd@...ts.infradead.org,
        Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Pratyush Yadav <p.yadav@...com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mtd: spi-nor: mt25qu: Ignore 6th ID byte

Dear maintainers!

On 22/11/2021 16:05, Michael Walle wrote:
> Thanks, so that's the SFDP data for the mt25qu256aba8e12-1sit part. and the
> jedec id is 20bb19104473, correct?

While we are at this part, I've encountered another issue:

The chip supports 1-1-1, 1-1-4 and 1-4-4 write OPs in extended SPI mode,
while only 1-1-0 erase. (as well as 4-4-4/4-4-0, but that's not the issue here,
I think).

Now the erase code (chip/sector) uses spi_nor_spimem_setup_op(nor, &op, nor->write_proto)
in both functions.

In my opinion, as I look into Micron or Macronix datasheets, write_proto has little to
do with erase_proto. (there is currently no separate erase_proto)

Before I come up with a totally wrong patch, wanted to ask your opinion, how should
it be solved, what do you think?

I do not see any erase-related tables for this in JESD216C.
I also cannot come up with an example of a chip with erase != 1-1-0.

Shall I hardcode 1-1-0 for erase?
Shall I introduce erase_proto? What would be the logic for its setting/discovery?

-- 
Best regards,
Alexander Sverdlin.