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

From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Cheng Ming Lin <linchengming884@gmail.com>
Cc: Michael Walle <mwalle@kernel.org>,
	 Pratyush Yadav <pratyush@kernel.org>,
	 Takahiro Kuwano <takahiro.kuwano@infineon.com>,
	Richard Weinberger <richard@nod.at>,
	 Vignesh Raghavendra <vigneshr@ti.com>,
	 linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
	 alvinzhou@mxic.com.tw,
	 Cheng Ming Lin <chengminglin@mxic.com.tw>
Subject: Re: [PATCH] mtd: spi-nor: Add support for MX25L12833F and MX25L12845G
Date: Thu, 28 May 2026 09:42:03 +0200	[thread overview]
Message-ID: <87eciwhtf8.fsf@bootlin.com> (raw)
In-Reply-To: <CAAyq3SY86mVwYtQMqhcZHjTxiD93awQZPDzHr8e5-+B9caNgbA@mail.gmail.com> (Cheng Ming Lin's message of "Thu, 28 May 2026 15:19:36 +0800")

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.

Thanks,
Miquèl

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