[PATCH net-next v7 08/12] dt-bindings: net: dsa: lantiq,gswip: add support for MII delay properties

[Daniel Golle]

Add support for standard tx-internal-delay-ps and rx-internal-delay-ps
properties on port nodes to allow fine-tuning of RGMII clock delays.

The GSWIP switch hardware supports delay values in 500 picosecond
increments from 0 to 3500 picoseconds, with a post-reset default of 2000
picoseconds for both TX and RX delays. The driver currently sets the
delay to 0 in case the PHY is setup to carry out the delay by the
corresponding interface modes ("rgmii-id", "rgmii-rxid", "rgmii-txid").

This corresponds to the driver changes that allow adjusting MII delays
using Device Tree properties instead of relying solely on the PHY
interface mode.

Signed-off-by: Daniel Golle <daniel@xxxxxxxxxxxxxx>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
---
v7: no changes

v6:
 * switch order of patches

v5: no changes

v4:
 * remove misleading defaults

v3:
 * redefine ports node so properties are defined actually apply
 * RGMII port with 2ps delay is 'rgmii-id' mode

v2: no changes

since RFC: no changes

 .../bindings/net/dsa/lantiq,gswip.yaml         | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/net/dsa/lantiq,gswip.yaml b/Documentation/devicetree/bindings/net/dsa/lantiq,gswip.yaml
index 809d0e9d0a15..929f6f8e4534 100644
--- a/Documentation/devicetree/bindings/net/dsa/lantiq,gswip.yaml
+++ b/Documentation/devicetree/bindings/net/dsa/lantiq,gswip.yaml
@@ -104,6 +104,20 @@ patternProperties:
             description:
               Configure the RMII reference clock to be a clock output
               rather than an input. Only applicable for RMII mode.
+          tx-internal-delay-ps:
+            enum: [0, 500, 1000, 1500, 2000, 2500, 3000, 3500]
+            description:
+              RGMII TX Clock Delay defined in pico seconds.
+              The delay lines adjust the MII clock vs. data timing.
+              If this property is not present the delay is determined by
+              the interface mode.
+          rx-internal-delay-ps:
+            enum: [0, 500, 1000, 1500, 2000, 2500, 3000, 3500]
+            description:
+              RGMII RX Clock Delay defined in pico seconds.
+              The delay lines adjust the MII clock vs. data timing.
+              If this property is not present the delay is determined by
+              the interface mode.
 
 required:
   - compatible
@@ -127,8 +141,10 @@ examples:
                     port@0 {
                             reg = <0>;
                             label = "lan3";
-                            phy-mode = "rgmii";
+                            phy-mode = "rgmii-id";
                             phy-handle = <&phy0>;
+                            tx-internal-delay-ps = <2000>;
+                            rx-internal-delay-ps = <2000>;
                     };
 
                     port@1 {
-- 
2.51.2