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

[Mika Westerberg]

Hi Tudor,

On Mon, May 31, 2021 at 02:29:59PM +0300, Mika Westerberg wrote:
> 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.

As the main SPI-NOR maintainer, what's your take on this?

Thanks!