dt-bindings: micrel-ksz90x1: Add rxc-dll and txc-dll properties

This commit adds two properties to control the RX DLL and TX DLL
2ns delay on RXC/TXC RGMII clock lines. This is especially needed
if the MAC does not provide TXC delay by itself.

Related-to: ELB-1299
Signed-off-by: Philippe Schenker <philippe.schenker@toradex.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/net/micrel-ksz90x1.txt b/Documentation/devicetree/bindings/net/micrel-ksz90x1.txt
index 2f71e7320576..9c84f3dc862c 100644
--- a/Documentation/devicetree/bindings/net/micrel-ksz90x1.txt
+++ b/Documentation/devicetree/bindings/net/micrel-ksz90x1.txt
@@ -63,8 +63,21 @@ KSZ9131:
   step is 100ps. Unlike KSZ9031, the values represent picoseccond delays.
   A negative value can be assigned as rxc-skew-psec = <(-100)>;.
 
+  The KSZ9131 provides additional 2ns delay register for RXC and TXC signals
+  with the RX DLL and TX DLL Control Register. This is a self adjusting delay
+  locked loop that maintains 2ns of delay for either RXC or TXC register.
+
   Optional properties:
 
+      - rxc-dll-2ns : 1 to enable 2ns dll controlled delay on RXC
+                      0 to disable this delay.
+                      If omitted, register will not be touched. The
+                      delay is enabled by default by hardware.
+      - txc-dll-2ns : 1 to enable 2ns dll controlled delay on TXC
+                      0 to disable this delay.
+                      If omitted, register will not be touched. The
+                      delay is disabled by default by hardware.
+
     Range of the value -700 to 2400, default value 0:
 
       - rxc-skew-psec : Skew control of RX clock pad