[PATCH net-next 1/3] dt-bindings: dp83867: add binding for io_impedance_ctrl nvmem cell

[Rasmus Villemoes]

We have a board where measurements indicate that the current three
options - leaving IO_IMPEDANCE_CTRL at the (factory calibrated) reset
value or using one of the two boolean properties to set it to the
min/max value - are too coarse.

There is no documented mapping from the 32 possible values of the
IO_IMPEDANCE_CTRL field to values in the range 35-70 ohms, and the
exact mapping is likely to vary from chip to chip. So add a DT binding
for an nvmem cell which can be populated during production with a
value suitable for each specific board.

Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
---
 .../devicetree/bindings/net/ti,dp83867.yaml    | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/net/ti,dp83867.yaml b/Documentation/devicetree/bindings/net/ti,dp83867.yaml
index 047d757e8d82..76ff08a477ba 100644
--- a/Documentation/devicetree/bindings/net/ti,dp83867.yaml
+++ b/Documentation/devicetree/bindings/net/ti,dp83867.yaml
@@ -31,6 +31,16 @@ properties:
   reg:
     maxItems: 1
 
+  nvmem-cells:
+    maxItems: 1
+    description:
+      Nvmem data cell containing the value to write to the
+      IO_IMPEDANCE_CTRL field of the IO_MUX_CFG register.
+
+  nvmem-cell-names:
+    items:
+      - const: io_impedance_ctrl
+
   ti,min-output-impedance:
     type: boolean
     description: |
@@ -42,9 +52,11 @@ properties:
     description: |
       MAC Interface Impedance control to set the programmable output impedance
       to a maximum value (70 ohms).
-      Note: ti,min-output-impedance and ti,max-output-impedance are mutually
-        exclusive. When both properties are present ti,max-output-impedance
-        takes precedence.
+      Note: Specifying an io_impedance_ctrl nvmem cell or one of the
+        ti,min-output-impedance, ti,max-output-impedance properties
+        are mutually exclusive. If more than one is present, an nvmem
+        cell takes precedence over ti,max-output-impedance, which in
+        turn takes precedence over ti,min-output-impedance.
 
   tx-fifo-depth:
     $ref: /schemas/types.yaml#/definitions/uint32
-- 
2.31.1