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Message-ID: <8735taxna8.fsf@geanix.com>
Date: Tue, 22 Jun 2021 11:26:55 +0200
From: Esben Haabendal <esben@...nix.com>
To: Rasmus Villemoes <linux@...musvillemoes.dk>
Cc: linux-mtd@...ts.infradead.org,
Frieder Schrempf <frieder.schrempf@...tron.de>,
Boris Brezillon <bbrezillon@...nel.org>,
Tudor Ambarus <tudor.ambarus@...rochip.com>,
Michael Walle <michael@...le.cc>,
Pratyush Yadav <p.yadav@...com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC 0/3] mtd: spi-nor: dealing with reused JEDEC id c22016
Rasmus Villemoes <linux@...musvillemoes.dk> writes:
> We use the Macronix chip mx25l3233f in a number of
> products.
>
> Unfortunately, it has the same JEDEC id as another chip which is
> already listed in macronix_parts[]. Since that other one does not
> support SFDP, and its data sheet warns against issuing commands not
> explicitly listed, we can't just do RDSFDP anyway and decide that it's
> an mx25l3205d when the chip returns garbage.
>
> For lack of better alternative, start allowing multiple entries with
> the same JEDEC id in the parts tables. That allows a correctly written
> device tree to specify the right chip, without being overruled by the
> "JEDEC knows better" heuristic, while being backwards-compatible (as
> long as new chips with recycled ids get added after the existing
> ones).
>
> While a step forward, this isn't quite a complete solution for our case:
>
> Some of our platforms are based on LS1021A, thus using the
> spi-fsl-qspi driver. Back in the 4.19 kernel, when the driver was
> fsl-quadspi, we couldn't get the flash recognized unless we
> monkey-patch-replaced the mx25l3205d entry with the mx25l3233f one
> (i.e. added the SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ bits) - we'd
> fail in spi_nor_select_read() because
> shared_hwcaps&SNOR_HWCAPS_READ_MASK would be empty. In contrast, with
> current master, the chip works with or without the third patch in this
> series, i.e. whether it is detected as a mx25l3205d or mx25l3233f. But
> the read performance is ~3 times worse than in our patched 4.19 - I
> haven't quite figured out why quad read doesn't seem to be used or
> work.
>
>
> Rasmus Villemoes (3):
> mtd: spi-nor: core: create helper to compare JEDEC id to struct
> flash_info
> mtd: spi-nor: core: compare JEDEC bytes to already found flash_info
> mtd: spi-nor: macronix: add entry for mx25l3233f
>
> drivers/mtd/spi-nor/core.c | 18 +++++++++++++-----
> drivers/mtd/spi-nor/macronix.c | 3 +++
> 2 files changed, 16 insertions(+), 5 deletions(-)
For whole series:
Acked-by: Esben Haabendal <esben@...nix.com>
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