[PATCH] spi: dt-bindings: spi-controller: Fix #address-cells for slave mode

[Geert Uytterhoeven <geert+renesas@xxxxxxxxx>]

Currently, the DT bindings for an SPI controller specify that
"#address-cells" must be fixed to one.  However, that applies to an SPI
controller in master mode only.  When running in SPI slave mode,
"#address-cells" should be zero.

Fix this making the value of "#address-cells" dependent on the presence
of "spi-slave".

Fixes: 0a1b929356830257 ("spi: Add YAML schemas for the generic SPI options")
Reported-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
---
Is this the right way to specify this?  I couldn't find an example, so
this needed some trial-and-error.

As of dtc commit 403cc79f06a135ae ("checks: Update SPI bus check for
'spi-slave'") and Linux commit c2e7075ca8303631 ("scripts/dtc: Update to
upstream version v1.4.7-57-gf267e674d145"), dtc knows about SPI slave.

However, when using "#address-cells = <0>" with W=1:

    Warning (avoid_unnecessary_addr_size): /soc/spi@e6e10000: unnecessary #address-cells/#size-cells without "ranges" or child "reg" property

Just removing #address-cells (using /delete-property/ in the board DTS)
to fix this warning causes:

    Warning (spi_bus_bridge): /soc/spi@e6e10000: incorrect #address-cells for SPI bus

as spi_bus_bridge() uses node_addr_cells(), which defaults to 2 (due to
dtc's ppc64 heritage? But node_size_cells() defaults to 1, not 2?).

How should this be fixed?
Should "#address-cells = <0>" be left out or not?
Should node_{addr,size}_cells() in dtc default to zero?

Thanks!
---
 .../devicetree/bindings/spi/spi-controller.yaml   | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/spi/spi-controller.yaml b/Documentation/devicetree/bindings/spi/spi-controller.yaml
index 1e0ca6ccf64bbd0a..ba2646258b94980e 100644
--- a/Documentation/devicetree/bindings/spi/spi-controller.yaml
+++ b/Documentation/devicetree/bindings/spi/spi-controller.yaml
@@ -20,7 +20,8 @@ properties:
     pattern: "^spi(@.*|-[0-9a-f])*$"
 
   "#address-cells":
-    const: 1
+    minimum: 0
+    maximum: 1
 
   "#size-cells":
     const: 0
@@ -52,6 +53,18 @@ properties:
     description:
       The SPI controller acts as a slave, instead of a master.
 
+if:
+  required:
+    [ spi-slave ]
+then:
+  properties:
+    "#address-cells":
+      const: 0
+else:
+  properties:
+    "#address-cells":
+      const: 1
+
 patternProperties:
   "^slave$":
     type: object
-- 
2.17.1