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

[Chris Brandt <Chris.Brandt@xxxxxxxxxxx>]

Hi Geert,

On Mon, Dec 9, 2019, Geert Uytterhoeven wrote:
> > +  reg:
> > +    minItems: 2
> > +    maxItems: 2
> > +    items:
> > +      - description: Registers
> > +      - description: Memory Mapped Address Space
> 
> The second one is not needed, if you would add "ranges" for the memory-mapped
> mode.


So for RZ/A2M:
  ranges = <0x0 0x20000000 0x10000000>;


> > +    # This example is for "External Address Space Read Mode"
> > +    spibsc: spi@1f800000 {
> > +        compatible = "renesas,r7s9210-spibsc";
> > +        reg = <0x1f800000 0x100>, <0x20000000 0x10000000>;
> > +        clocks = <&cpg CPG_MOD 83>;
> > +        power-domains = <&cpg>;
> > +        interrupts = <GIC_SPI 445 IRQ_TYPE_LEVEL_HIGH>;
> > +        #address-cells = <1>;
> > +        #size-cells = <0>;
> > +    };
> > +    flash@20000000 {
> 
> This does not describe the hardware topology: the flash node should be a
> subnode of the spibsc node, as it relies on the spibsc being clocked.

So for the "XIP" case, I originally tried adding an "mtd-rom" flash node
under the spibsc node, but then the mtd-rom part never got probed. I 
guess that was because it didn't register a SPI controller.


But, I guess if we go your method...
>     spibsc: spi@1f800000 {
>                 compatible = "renesas,r7s9210-spibsc", "simple-pm-bus";

Then after the spibsc driver fails and the "simple-pm-bus" driver tries,
it will succeed and the simple-pm-bus driver will start probing the 
subnodes (in my case, the mtd-rom).


> and applying "[PATCH] mtd: maps: physmap: Add minimal Runtime PM support"[1],
> the memory-mapped case should work, without your spibsc driver.

Good.
So we can add the SPI-BSC clocks for RZ/A1 and RZ/A2 (even without the 
SPI-BSC driver) and still have a working solution for XIP_KERNEL.



So in the end, this all seems like a very simple solution to get 
everything I wanted with minimal complexity.

But, if Sergei is going a completely different route for R-Car, I guess 
I need to understand that first what he is trying to do before I really
push for this driver getting in.
Again, this driver was only when using the SPI-BSC HW, not the full 
(different) R/W HyperFlash controller HW. That would be a separate driver.

Chris