RE: [PATCH v2 1/3] Revert "mtd: spi-nor: remove Fujitsu MB85RS1MT support"

[<Takahiro.Kuwano@infineon.com>]

Hi,

> Hi Takahiro,
> 
> On 30/06/2026 19:47, Takahiro.Kuwano@infineon.com wrote:
> > Hi,
> >
> >> This reverts commit d9cd5c9a6fe26d544551cfaa94fb0abc50c0b895.
> >>
> >> The commit that removed support for this chip claimed that the at25
> >> driver was the correct driver to use for this chip. However, the at25
> >> driver exposes the chip as an NVMEM device, not a MTD device, so it's
> >> not a suitable replacement for users that want to mount a file system
> >> over the chip.
> >>
> > What file system do you use?
> > The size of FRAM chips (hundreds of KB) sounds too small for file
> > systems.
> 
> We're using ext2. Technically we want this for the MB85RS4MT which is
> added in patch 3 of this series.
> 
We don't add any FRAM chips in SPI-NOR...

> The use is for a small amount of additional storage separate to the main
> system NAND flash for some small "critical" files that we don't want to
> lose. We've been using devices like the mchp23lcv1024 and mr25h40 on
> other products for some time.
> 
For that use, how about using tmpfs with NVMEM backup?

> >> Revert the change that removed support for the MB85RS1MT FRAM chip.
> >>
> >> Signed-off-by: Ronan Dalton <ronan.dalton@alliedtelesis.co.nz>
> >> Cc: linux-kernel@vger.kernel.org
> >> Cc: linux-mtd@lists.infradead.org
> >> Cc: Pratyush Yadav <pratyush@kernel.org>
> >> Cc: Michael Walle <mwalle@kernel.org>
> >> Cc: Takahiro Kuwano <takahiro.kuwano@infineon.com>
> >> Cc: Miquel Raynal <miquel.raynal@bootlin.com>
> >> Cc: Richard Weinberger <richard@nod.at>
> >> Cc: Vignesh Raghavendra <vigneshr@ti.com>
> >> Cc: Chris Packham <chris.packham@alliedtelesis.co.nz>
> >> Cc: Aryan Srivastava <aryan.srivastava@alliedtelesis.co.nz>
> >> ---
> >> Changes in v2:
> >> - No changes
> >>
> >>   drivers/mtd/spi-nor/Makefile  |  1 +
> >>   drivers/mtd/spi-nor/core.c    |  1 +
> >>   drivers/mtd/spi-nor/core.h    |  1 +
> >>   drivers/mtd/spi-nor/fujitsu.c | 21 +++++++++++++++++++++
> >>   4 files changed, 24 insertions(+)
> >>   create mode 100644 drivers/mtd/spi-nor/fujitsu.c
> >>
> >> diff --git a/drivers/mtd/spi-nor/Makefile b/drivers/mtd/spi-nor/Makefile
> >> index 5dd9c35f6b6f..9216a5a29a2b 100644
> >> --- a/drivers/mtd/spi-nor/Makefile
> >> +++ b/drivers/mtd/spi-nor/Makefile
> >> @@ -5,6 +5,7 @@ spi-nor-objs                    += atmel.o
> >>   spi-nor-objs                   += eon.o
> >>   spi-nor-objs                   += esmt.o
> >>   spi-nor-objs                   += everspin.o
> >> +spi-nor-objs                   += fujitsu.o
> >>   spi-nor-objs                   += gigadevice.o
> >>   spi-nor-objs                   += intel.o
> >>   spi-nor-objs                   += issi.o
> >> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> >> index ccf4396cdcd0..d5ebbfd3fa7f 100644
> >> --- a/drivers/mtd/spi-nor/core.c
> >> +++ b/drivers/mtd/spi-nor/core.c
> >> @@ -2009,6 +2009,7 @@ static const struct spi_nor_manufacturer *manufacturers[] = {
> >>          &spi_nor_eon,
> >>          &spi_nor_esmt,
> >>          &spi_nor_everspin,
> >> +       &spi_nor_fujitsu,
> >>          &spi_nor_gigadevice,
> >>          &spi_nor_intel,
> >>          &spi_nor_issi,
> >> diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
> >> index ba2d1a862c9d..a4d906e6d07d 100644
> >> --- a/drivers/mtd/spi-nor/core.h
> >> +++ b/drivers/mtd/spi-nor/core.h
> >> @@ -606,6 +606,7 @@ extern const struct spi_nor_manufacturer spi_nor_atmel;
> >>   extern const struct spi_nor_manufacturer spi_nor_eon;
> >>   extern const struct spi_nor_manufacturer spi_nor_esmt;
> >>   extern const struct spi_nor_manufacturer spi_nor_everspin;
> >> +extern const struct spi_nor_manufacturer spi_nor_fujitsu;
> >>   extern const struct spi_nor_manufacturer spi_nor_gigadevice;
> >>   extern const struct spi_nor_manufacturer spi_nor_intel;
> >>   extern const struct spi_nor_manufacturer spi_nor_issi;
> >> diff --git a/drivers/mtd/spi-nor/fujitsu.c b/drivers/mtd/spi-nor/fujitsu.c
> >> new file mode 100644
> >> index 000000000000..69cffc5c73ef
> >> --- /dev/null
> >> +++ b/drivers/mtd/spi-nor/fujitsu.c
> >> @@ -0,0 +1,21 @@
> >> +// SPDX-License-Identifier: GPL-2.0
> >> +/*
> >> + * Copyright (C) 2005, Intec Automation Inc.
> >> + * Copyright (C) 2014, Freescale Semiconductor, Inc.
> >> + */
> >> +
> >> +#include <linux/mtd/spi-nor.h>
> >> +
> >> +#include "core.h"
> >> +
> >> +static const struct flash_info fujitsu_nor_parts[] = {
> >> +       /* Fujitsu */
> >> +       { "mb85rs1mt", INFO(0x047f27, 0, 128 * 1024, 1)
> >> +               FLAGS(SPI_NOR_NO_ERASE) },
> >> +};
> >> +
> >> +const struct spi_nor_manufacturer spi_nor_fujitsu = {
> >> +       .name = "fujitsu",
> >> +       .parts = fujitsu_nor_parts,
> >> +       .nparts = ARRAY_SIZE(fujitsu_nor_parts),
> >> +};
> >> --
> >> 2.54.0
> > Thanks,
> > Takahiro
> >