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Message-Id: <D3E0BKGQIZ9R.1ULZZ93E18VGM@kernel.org>
Date: Mon, 12 Aug 2024 16:36:11 +0200
From: "Michael Walle" <mwalle@...nel.org>
To: "Pratyush Yadav" <pratyush@...nel.org>
Cc: "Tudor Ambarus" <tudor.ambarus@...aro.org>, "Miquel Raynal"
<miquel.raynal@...tlin.com>, "Richard Weinberger" <richard@....at>,
"Vignesh Raghavendra" <vigneshr@...com>, <linux-mtd@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mtd: spi-nor: winbond: add Zetta ZD25Q128C support
Hi,
> > Zetta normally uses BAh as its vendor ID. But for the ZD25Q128C they
> > took the one from Winbond and messed up the size parameters in SFDP.
> > Most functions seem compatible with the W25Q128, we just have to fix up
> > the size.
> >
> > Link: http://www.zettadevice.com/upload/file/20150821/DS_Zetta_25Q128_RevA.pdf
> > Link: https://www.lcsc.com/datasheet/lcsc_datasheet_2312081757_Zetta-ZD25Q128CSIGT_C19626875.pdf
> > Signed-off-by: Michael Walle <mwalle@...nel.org>
> > ---
> [...]
> > diff --git a/drivers/mtd/spi-nor/winbond.c b/drivers/mtd/spi-nor/winbond.c
> > index e065e4fd42a3..9f7ce5763e71 100644
> > --- a/drivers/mtd/spi-nor/winbond.c
> > +++ b/drivers/mtd/spi-nor/winbond.c
> > @@ -17,6 +17,31 @@
> > SPI_MEM_OP_NO_DUMMY, \
> > SPI_MEM_OP_DATA_OUT(1, buf, 0))
> >
> > +static int
> > +w25q128_post_bfpt_fixups(struct spi_nor *nor,
> > + const struct sfdp_parameter_header *bfpt_header,
> > + const struct sfdp_bfpt *bfpt)
> > +{
> > + /*
> > + * Zetta ZD25Q128C is a clone of the Winbond device. But the encoded
> > + * size is really wrong. It seems that they confused Mbit with MiB.
> > + * Thus the flash is discovered as a 2MiB device.
> > + */
> > + if (bfpt_header->major == SFDP_JESD216_MAJOR &&
> > + bfpt_header->minor == SFDP_JESD216_MINOR &&
> > + nor->params->size == SZ_2M &&
> > + nor->params->erase_map.regions[0].size == SZ_2M) {
> > + nor->params->size = SZ_16M;
> > + nor->params->erase_map.regions[0].size = SZ_16M;
> > + }
>
> Since the size is 16 MiB for both Zetta and Winbond, why do you have
> these conditions here? Why not just do it unconditionally? What
> situation do you want to protect against?
Two things, I want to make sure, the values I'll overwrite (which
were set indirectly by the SFDP data I check here) are really the
"before" value I expect them to be. And secondly, I want to
fingerprint the SFDP as accurately as possible. I mean you wouldn't
need the SFDP version either. Think of a preparation for a possible
.match() callback in zetta.c. That would probably look like this,
i.e. check the flash id and these four conditions.
What are your concerns?
-michael
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