[PATCH net-next v4 1/2] dts: Add a binding for Synopsys emac max-frame-size

[Vince Bridgers <vbridgers2013@gmail.com>]

This change adds a parameter for the Synopsys 10/100/1000
stmmac Ethernet driver to configure the maximum frame
size supported by the EMAC driver. Synopsys allows the FIFO
sizes to be configured when the cores are built for a particular
device, but do not provide a way for the driver to read
information from the device about the maximum MTU size
supported as limited by the device's FIFO size.

Signed-off-by: Vince Bridgers <vbridgers2013@gmail.com>
---
V4: add comments to explain use of max-frame-size with respect
    to inconsistent definition and use in the ePAPR v1.1 spec
V3: change snps,max-frame-size to max-frame-size
V2: change snps,max-mtu to snps,max-frame-size
---
 Documentation/devicetree/bindings/net/stmmac.txt |   13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/net/stmmac.txt b/Documentation/devicetree/bindings/net/stmmac.txt
index eba0e5e..d553be2 100644
--- a/Documentation/devicetree/bindings/net/stmmac.txt
+++ b/Documentation/devicetree/bindings/net/stmmac.txt
@@ -29,7 +29,17 @@ Required properties:
 				ignored if force_thresh_dma_mode is set.
 
 Optional properties:
-- mac-address: 6 bytes, mac address
+- mac-address:		6 bytes, mac address
+- max-frame-size:	Maximum frame size permitted. This parameter is useful
+			since different implementations of the Synopsys MAC may
+			have different FIFO sizes depending on the selections
+			made in Synopsys Core Consultant. Note that the usage
+			is inconsistent with the definition in the ePAPR v1.1
+			specification, as it defines max-frame-size inclusive
+			of the MAC DA, SA, Ethertype and CRC while usage is
+			consistent with the IEEE definition of MAC Client
+			Data, which is sans the MAC DA, SA, Ethertype and
+			CRC.
 
 Examples:
 
@@ -40,5 +50,6 @@ Examples:
 		interrupts = <24 23>;
 		interrupt-names = "macirq", "eth_wake_irq";
 		mac-address = [000000000000]; /* Filled in by U-Boot */
+		max-frame-size = <3800>;
 		phy-mode = "gmii";
 	};
-- 
1.7.9.5