[PATCH net-next v4 1/2] net: dt-bindings: add RGMII TX delay configuration to meson8b-dwmac

[Martin Blumenstingl]

This allows configuring the RGMII TX clock delay. The RGMII clock is
generated by underlying hardware of the the Meson 8b / GXBB DWMAC glue.
The configuration depends on the actual hardware (no delay may be
needed due to the design of the actual circuit, the PHY might add this
delay, etc.).

Signed-off-by: Martin Blumenstingl <martin.blumenstingl at googlemail.com>
Tested-by: Neil Armstrong <narmstrong at baylibre.com>
Acked-by: Rob Herring <robh at kernel.org>
---
 Documentation/devicetree/bindings/net/meson-dwmac.txt | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/Documentation/devicetree/bindings/net/meson-dwmac.txt b/Documentation/devicetree/bindings/net/meson-dwmac.txt
index 89e62ddc69ca..f8bc54094e3c 100644
--- a/Documentation/devicetree/bindings/net/meson-dwmac.txt
+++ b/Documentation/devicetree/bindings/net/meson-dwmac.txt
@@ -25,6 +25,20 @@ Required properties on Meson8b and newer:
 		- "clkin0" - first parent clock of the internal mux
 		- "clkin1" - second parent clock of the internal mux
 
+Optional properties on Meson8b and newer:
+- amlogic,tx-delay-ns:	The internal RGMII TX clock delay (provided
+			by this driver) in nanoseconds. Allowed values
+			are: 0ns, 2ns, 4ns, 6ns.
+			This must be configured when the phy-mode is
+			"rgmii" (typically a value of 2ns is used in
+			this case).
+			When phy-mode is set to "rgmii-id" or
+			"rgmii-txid" the TX clock delay is already
+			provided by the PHY. In that case this
+			property should be set to 0ns (which disables
+			the TX clock delay in the MAC to prevent the
+			clock from going off because both PHY and MAC
+			are adding a delay).
 
 Example for Meson6:
 
-- 
2.11.0