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

Rasmus Villemoes
2022-06-06T20:22:45Z

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@rasmusvillemoes.dk>
---
.../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