Re: [PATCH] mtd: spi-nor: intel-spi: Add support for second flash chip

[Mika Westerberg <mika.westerberg@linux.intel.com>]

Hi,

On Wed, May 26, 2021 at 11:31:58AM +0200, Michael Walle wrote:
> > Oh, I see now this commit:
> > 
> > a314f6367787 ("mtd: spi-nor: Convert cadence-quadspi to use spi-mem
> > framework")
> > 
> > So "SPI MEM" means generic SPI subsystem for memory mapped devices.
> > Unfortunately Intel controller at least is not capable of running
> > generic SPI transactions. It only supports accessing SPI-NOR flashes and
> > for those there is small set of commands that supports. I don't think it
> > is even possible to convert the driver to generic SPI subsystem.
> 
> AFAIK it stands for SPI memory device (memory mapped is not a requirement).
> Eg. spi-nxp-fspi doesn't support generic SPI devices either, but just SPI
> flashes. So I'd guess SPI MEM is exactly what you are looking for.

OK, I see that there is ->mem_ops that can be used to implement
different higher level commands. What I'm not seeing is that how the
child SPI flash is created using this scheme? DeviceTree and ACPI are
supported fine but what about scanning? I mean the intel_spi driver has
this:

  spi_nor_scan(&ispi->nor, NULL, &hwcaps);

But if the driver is to be moved under drivers/spi/* you can't really
call these functions anymore or can you? Or the point is to keep the
driver under controllers/ and just call spi_nor_scan(), and in addition
implement the new mem_ops?

Thanks in advance and sorry about many questions but there does not seem
to be a conversion guide nor any (non-DT/ACPI) examples that I can take
a look. :-)

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