[RFC PATCH net-next] dt-bindings: dpll: Add per-channel Ethernet reference property

[Ivan Vecera <ivecera@redhat.com>]

In case of SyncE scenario a DPLL channels generates a clean frequency
synchronous Ethernet clock (SyncE) and feeds it into the NIC transmit
path. The DPLL channel can be locked either to the recovered clock
from the NIC's PHY (Loop timing scenario) or to some external signal
source (e.g. GNSS) (Externally timed scenario).

The example shows both situations. NIC1 recovers the input SyncE signal
that is used as an input reference for DPLL channel 1. The channel locks
to this signal, filters jitter/wander and provides holdover. On output
the channel feeds a stable, phase-aligned clock back into the NIC1.
In the 2nd case the DPLL channel 2 locks to a master clock from GNSS and
feeds a clean SyncE signal into the NIC2.

		   +-----------+
		+--|   NIC 1   |<-+
		|  +-----------+  |
		|                 |
		| RxCLK     TxCLK |
		|                 |
		|  +-----------+  |
		+->| channel 1 |--+
+------+	   |-- DPLL ---|
| GNSS |---------->| channel 2 |--+
+------+  RefCLK   +-----------+  |
				  |
			    TxCLK |
				  |
		   +-----------+  |
		   |   NIC 2   |<-+
		   +-----------+

In the situations above the DPLL channels should be registered into
the DPLL sub-system with the same Clock Identity as PHCs present
in the NICs (for the example above DPLL channel 1 uses the same
Clock ID as NIC1's PHC and the channel 2 as NIC2's PHC).

Because a NIC PHC's Clock ID is derived from the NIC's MAC address,
add a per-channel property 'ethernet-handle' that specifies a reference
to a node representing an Ethernet device that uses this channel
to synchronize its hardware clock. Additionally convert existing
'dpll-types' list property to 'dpll-type' per-channel property.

Suggested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
---
 .../devicetree/bindings/dpll/dpll-device.yaml | 40 ++++++++++++++++---
 .../bindings/dpll/microchip,zl30731.yaml      | 29 +++++++++++++-
 2 files changed, 62 insertions(+), 7 deletions(-)

diff --git a/Documentation/devicetree/bindings/dpll/dpll-device.yaml b/Documentation/devicetree/bindings/dpll/dpll-device.yaml
index fb8d7a9a3693f..798c5484657cf 100644
--- a/Documentation/devicetree/bindings/dpll/dpll-device.yaml
+++ b/Documentation/devicetree/bindings/dpll/dpll-device.yaml
@@ -27,11 +27,41 @@ properties:
   "#size-cells":
     const: 0
 
-  dpll-types:
-    description: List of DPLL channel types, one per DPLL instance.
-    $ref: /schemas/types.yaml#/definitions/non-unique-string-array
-    items:
-      enum: [pps, eec]
+  channels:
+    type: object
+    description: DPLL channels
+    unevaluatedProperties: false
+
+    properties:
+      "#address-cells":
+        const: 1
+      "#size-cells":
+        const: 0
+
+    patternProperties:
+      "^channel@[0-9a-f]+$":
+        type: object
+        description: DPLL channel
+        unevaluatedProperties: false
+
+        properties:
+          reg:
+            description: Hardware index of the DPLL channel
+            maxItems: 1
+
+          dpll-type:
+            description: DPLL channel type
+            $ref: /schemas/types.yaml#/definitions/string
+            enum: [pps, eec]
+
+          ethernet-handle:
+            description:
+              Specifies a reference to a node representing an Ethernet device
+              that uses this channel to synchronize its hardware clock.
+            $ref: /schemas/types.yaml#/definitions/phandle
+
+        required:
+          - reg
 
   input-pins:
     type: object
diff --git a/Documentation/devicetree/bindings/dpll/microchip,zl30731.yaml b/Documentation/devicetree/bindings/dpll/microchip,zl30731.yaml
index 17747f754b845..bc6d6cc1dd47f 100644
--- a/Documentation/devicetree/bindings/dpll/microchip,zl30731.yaml
+++ b/Documentation/devicetree/bindings/dpll/microchip,zl30731.yaml
@@ -44,9 +44,26 @@ examples:
       #size-cells = <0>;
 
       dpll@70 {
+        #address-cells = <0>;
+        #size-cells = <0>;
         compatible = "microchip,zl30732";
         reg = <0x70>;
-        dpll-types = "pps", "eec";
+
+        channels {
+          #address-cells = <1>;
+          #size-cells = <0>;
+
+          channel@0 {
+            reg = <0>;
+            dpll-type = "pps";
+          };
+
+          channel@1 {
+            reg = <1>;
+            dpll-type = "eec";
+            ethernet-handle = <&ethernet0>;
+          };
+        };
 
         input-pins {
           #address-cells = <1>;
@@ -84,7 +101,15 @@ examples:
         reg = <0x70>;
         spi-max-frequency = <12500000>;
 
-        dpll-types = "pps";
+        channels {
+          #address-cells = <1>;
+          #size-cells = <0>;
+
+          channel@0 {
+            reg = <0>;
+            dpll-type = "pps";
+          };
+        };
 
         input-pins {
           #address-cells = <1>;
-- 
2.49.1