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

[Mika Westerberg]

Hi guys,

On Wed, May 26, 2021 at 01:28:16PM +0300, Mika Westerberg wrote:
> 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. :-)

Can you provide some guidance here? So in order to use the generic SPI
subsystem with "SPI MEM" parts of it, I would need to be able to create
the child SPI-NOR flash device without using ACPI or DT (as these
systems do not have any ACPI/DT description), or use spi_nor_scan() but
none of the driver under drivers/spi are calling it.

Thanks!