linux-kernel - Re: [PATCH 2/3] mtd: spi-nor: Add a driver for the VIA/WonderMedia serial flash controller

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Message-ID: <mafs01psu89sx.fsf@kernel.org>
Date: Mon, 12 May 2025 09:20:30 +0000
From: Pratyush Yadav <pratyush@...nel.org>
To: Alexey Charkov <alchark@...il.com>
Cc: Mark Brown <broonie@...nel.org>,  Rob Herring <robh@...nel.org>,
  Krzysztof Kozlowski <krzk+dt@...nel.org>,  Conor Dooley
 <conor+dt@...nel.org>,  Tudor Ambarus <tudor.ambarus@...aro.org>,
  Pratyush Yadav <pratyush@...nel.org>,  Michael Walle <mwalle@...nel.org>,
  Miquel Raynal <miquel.raynal@...tlin.com>,  Richard Weinberger
 <richard@....at>,  Vignesh Raghavendra <vigneshr@...com>,  Krzysztof
 Kozlowski <krzk@...nel.org>,  linux-spi@...r.kernel.org,
  devicetree@...r.kernel.org,  linux-kernel@...r.kernel.org,
  linux-mtd@...ts.infradead.org,  linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/3] mtd: spi-nor: Add a driver for the VIA/WonderMedia
 serial flash controller

Hi Alexey,

On Sat, May 10 2025, Alexey Charkov wrote:

> The controller is tailored to SPI NOR flash memory and abstracts away all
> SPI communications behind a small set of MMIO registers and a physical
> memory mapping of the actual chip contents.
>
> It doesn't expose chip probing functions beyond reading the ID though, so
> use lower level chip opcodes via the "programmable command mode" of the
> controller and the kernel's SPI NOR framework to avoid hard-coding chip
> parameters for each ID the way the vendor kernel does it.
>
> Currently tested on a WonderMedia WM8950 SoC with a Macronix MX25L4005A
> flash chip (APC Rock board), but should work on all VIA/WonderMedia SoCs
>
> Signed-off-by: Alexey Charkov <alchark@...il.com>
> ---
>  MAINTAINERS                                  |   1 +
>  drivers/mtd/spi-nor/controllers/Kconfig      |  14 +
>  drivers/mtd/spi-nor/controllers/Makefile     |   1 +
>  drivers/mtd/spi-nor/controllers/wmt-sflash.c | 525 +++++++++++++++++++++++++++

Drivers in drivers/mtd/spi-nor/controllers/ are deprecated, and we want
to eventually get rid of the API. The expected way is for drivers to use
SPI MEM (drivers/spi/spi-mem.c). SPI MEM drivers are usually more
general and not tailored specifically to SPI NOR flashes, so it might be
a bit tricky to write drivers for specialized hardware with it. But I
think the drivers/spi/spi-intel.c driver is written for similar kind of
hardware so it should be possible.
>
[...]

-- 
Regards,
Pratyush Yadav