Re: [PATCH 0/2] mtd: hyperbus: Add support for Infineon S26Hx-T

[Tudor Ambarus <tudor.ambarus@linaro.org>]

+ Sergei, Geert, Mark & linux-spi

Hi, Sergei,

On 23.05.2023 07:22, Tudor Ambarus wrote:
> Hi, Takahiro, Vignesh,
> 
> 
> On 07.04.2023 09:11, tkuw584924@gmail.com wrote:
>> From: Takahiro Kuwano <Takahiro.Kuwano@infineon.com>
>>
>> This sereis adds support for Infineon S26HL-T/S26HS-T flash family.
>> https://www.infineon.com/dgdl/Infineon-S26HS01GTGABHM020-DataSheet-v01_00-EN.pdf?fileId=8ac78c8c7f2a768a017f52f2f5182c91
>>
>> This family supports two interface modes, SPI mode and Hyperbus mode. The mode
>> can be switched at rutime. The default mode is selected by ordering option
>> and non-volatile user configuration. In hyperbus mode, the device is compatible
>> with S26KL-S/S26KS-S hyperflash family that supports hyperbus only so one of
>> use cases of S26Hx-T is replacement of (or migration from) S26Kx-S. This patch
>> set focuses on particular usage that the device is pre-configured as hyperbus
>> mode for compatibility with S26Kx-S.
> 
> I'm questioning the overall hyperbus software architecture, not your
> patches per se. IMO hyperbus framework should have been written on top
> of SPIMEM and the controllers be placed in drivers/spi/. So I'd first
> address the SPIMEM adoption before adding/accepting new support. Would
> love to hear more from Vignesh.
> 

RPC is the only multi IO SPI controller that's upstreamed and capable of
dealing with hyperflashes, but there are others which are not upstreamed
yet (microchip).

Struct ``struct rpcif_op`` [1] duplicates the contents of ``struct
spi_mem_op`` [2] which could have been avoided if hyperflash driver was
extended with SPI MEM support. This way the RPC hyperbus driver, which
is an SPI controller, could have been moved to drivers/spi.

Sergei, do you remember why we haven't used SPI MEM for hyberbus since
the beginning? Was it something that we aimed for in a future patch set?

Thanks,
ta

[1]
https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git/tree/include/memory/renesas-rpc-if.h?h=mtd/for-6.8#n22

[2]
https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git/tree/include/linux/spi/spi-mem.h?h=mtd/for-6.8#n99