RE: [PATCH v2 2/6] dt-bindings: spi: Document Renesas SPIBSC bindings

[Chris Brandt <Chris.Brandt@xxxxxxxxxxx>]

On Tue, Dec 10, 2019, Sergei Shtylyov wrote:
> >> +    items:
> >> +      - description: Registers
> >> +      - description: Memory Mapped Address Space
> >
> > The second one is not needed, if you would add "ranges" for the
> > memory-mapped mode.
> 
>    I'm not sure we can do that. The flash bus is accessed via a window with
> the high bits in the DREAR reg, even in the direct read mode...

The purpose of this driver was to allow R/W access using the existing 
MTD/SPI layer.
When the HW is operating in this mode, the driver basically just needs 
to read the vale of "ranges" in the DT to know the base address, and 
that's all it uses it for.

If the HW is going to be used in 'direct read mode', then the MTD/SPI 
layer will not be used. Instead the MTD/ROM driver will be used.
Configuring the HW for this mode is out of scope at the moment and 
should be done in the boot loader (just like DDR or SDRAM is configured by 
the boot loader).
The MTD/ROM driver will also handle all the ioremapping based on the 
values in the partition values under the flash node.

Chris