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Date:   Fri, 03 Sep 2021 13:47:29 +0200
From:   Michael Walle <michael@walle.cc>
To:     Andrea Zanotti <andreazanottifo@gmail.com>
Cc:     Tudor Ambarus <tudor.ambarus@microchip.com>,
        Pratyush Yadav <p.yadav@ti.com>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mtd: spi-nor: micron-st: added support for np8p128ax60
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Hi Andrea,

Am 2021-09-01 13:20, schrieb Andrea Zanotti:
> I performed the test with drivers/misc/eeprom/at25.c.
> 
> I configured the DTS as such:
> spi_pcm@0 {
> compatible = "atmel,at25";
> reg = <0>;
> spi-max-frequency = <50000000>;
> size = <16777216>;
> pagesize = <64>;
> address-width = <24>;
> label = "micron_pcm";
> };
> and activated the driver itself in the kernel configuration.
> 
> I think the system is recognizing it:
> # ls -l /sys/bus/spi/devices/spi0.0/eeprom
> -rw-------    1 root     root      16777216 Jan  1 00:01
> /sys/bus/spi/devices/spi0.0/eeprom
> 
> However, if I am not wrong (again, please correct me if I am wrong)
> this driver does not
> work with the MTD layer (I am booting with the following cmdline 
> bootargs:
> mtdparts=micron_pcm:128k(bootstrap),128k(fdt),10M(kernel/rootfs),-(spare)
> and I expected to have the same partitions as before, but of course
> they are missing.)

You are correct, there is no mtd layer for an eeprom device. If you
need the partitioning, the at25 won't work.

> I am checking the Company ID on the document "JEP106BC", revisioned on
> June 2020,
> downloaded from here 
> https://www.jedec.org/system/files/docs/JEP106BC.pdf.

Btw theres one from Feb 2021, but it doesn't really matter.

> STMicroelectronics should be 20
> Micron should be 2C

which matches the micron_parts[] and st_parts[].

> Intel is advertised as 89, in Table 1 "Manufacturer's Identification 
> Code".
> 
> How do you suggest to proceed?

I'm not sure, it this flash was originally made by intel or if its a
mistake. If its made by intel it probably should go into intel.c

Tudor is working on a larger patchset which addresses flash id
collisions [1]. If it is a mistake, then it should probably go into
the new collisions table which is introduced in this patchset.

Btw. AFAIK new flash additions are delayed until that patchset
is merged.

[1] 
https://lore.kernel.org/linux-mtd/20210727045222.905056-1-tudor.ambarus@microchip.com/

-michael