Re: [PATCH] mtd: spi-nor: Add support for MX25L12833F and MX25L12845G

[Michael Walle]

On Mon Jun 1, 2026 at 2:56 AM CEST, Cheng Ming Lin wrote:
> Hi Michael,
>
> Michael Walle <mwalle@xxxxxxxxxx> 於 2026年5月28日週四 下午3:52寫道：
>>
>> Hi,
>>
>> On Thu May 28, 2026 at 9:42 AM CEST, Miquel Raynal wrote:
>> > Hi Cheng Ming,
>> >
>> >>> It looks like you're getting bitten by the ID reuse. You can't just
>> >>> unconditionally add the quad PP because as far as I can see the
>> >>> MX25L12805D [1] is just a standard single bit i/o flash and doesn't
>> >>> support the 4PP.
>> >>
>> >> You are absolutely right. Thanks for catching this.
>> >>
>> >> The MX25L12805D is indeed a much older product (released around 2009).
>> >> Since the initial JESD216 SFDP standard wasn't published until 2011,
>> >> I double-checked with our internal PM and confirmed that the MX25L12805D
>> >> does not support SFDP at all.
>> >>
>> >> Since the newer flashes (MX25L12833F and MX25L12845G) do support SFDP,
>> >> we could use this as a differentiator to distinguish them from the legacy
>> >> MX25L12805D.
>> >>
>> >> What if we try to read the SFDP signature (RDSFDP) in the fixup hook?
>> >> If a valid SFDP signature is detected, we can safely identify it as the
>> >> newer flash and apply the SNOR_HWCAPS_PP_1_4_4 capability. If there is
>> >> no SFDP signature, we leave it as is for the legacy MX25L12805D.
>> >>
>> >> Do you think this approach is feasible and acceptable? If so, I will
>> >> implement this logic and submit a v2 patch.
>> >
>> > The ->post_sfdp() fixup hook is documented as "not called for SPI NORs
>> > that do not support SFDP". Alternatively, I believe an earlier hook,
>> > like ->post_bfpt() could also work since it does not seem to run on
>> > non SFDP compatible flashes.
>>
>> Moreover:
>>
>>  *    spi_nor_post_sfdp_fixups() is called after the SFDP tables are parsed.
>>  *    It is used to tweak various flash parameters when information provided
>>  *    by the SFDP tables are wrong.
>>
>> And it looks like that is the case for these flashes. Also, please
>> provide a comment on the fixup describing that the flash misses that
>> property. Basically, what you've written in the commit message.
>
> I am currently working on the flash part 0xc22018 and I am planning to
> add its size back to the flash info table. However, I encountered an
> issue regarding the fixup hooks.
>
> Since this specific flash does not support dual, quad, or octal reads,
> the core logic in spi_nor_init_params_deprecated() determines that SFDP
> parsing is not needed. Because the SFDP parsing is skipped, the post_bfpt
> or post_sfdp hooks are never triggered, which prevents us from applying
> the necessary fixups as we expected.
>
> I initially considered asking about the possibility of removing this
> specific check in spi_nor_init_params_deprecated(), which would allow
> all SPI-NOR flashes to go through SFDP parsing by default (unless
> SPI_NOR_SKIP_SFDP is explicitly set).

Oops, I've forgot to add you on CC. Sorry. I've just send a series
to get rid of that legacy handling. Please give it a try on your
flashes.

[1] https://lore.kernel.org/linux-mtd/20260601125438.3481722-1-mwalle@xxxxxxxxxx/

-michael

> However, I am aware that forcing SFDP parsing globally on all legacy
> 1-1-1 flashes might be risky. Flashes predating the JESD216 standard
> might return garbage data when the SFDP opcode (0x5A) is issued,
> potentially causing regressions if the garbage data accidentally matches
> the SFDP signature.
>
> If dropping this global check is indeed considered too risky for older
> hardware, would it be acceptable to use the late_init hook to handle
> this flash individually? The idea would be to manually check and parse
> the SFDP table exclusively for 0xc22018 within its own fixup, ensuring
> that no other legacy 1-1-1 flashes are affected by this change.
>
> Any thoughts or guidance on whether this late_init approach is the right
> way to go would be greatly appreciated.

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