[PATCH net-next v2 2/3] net: ethernet: fec: Allow configuration of MDIO bus speed

[Andrew Lunn <andrew@lunn.ch>]

MDIO busses typically operate at 2.5MHz. However many devices can
operate at faster speeds. This then allows more MDIO transactions per
second, useful for Ethernet switch statistics, or Ethernet PHY TDR
data. Allow the bus speed to be configured, using the standard
"clock-frequency" property, which i2c busses use to indicate the bus
speed.

Suggested-by: Chris Healy <Chris.Healy@zii.aero>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
---
 Documentation/devicetree/bindings/net/fsl-fec.txt |  1 +
 Documentation/devicetree/bindings/net/mdio.yaml   |  4 ++++
 drivers/net/ethernet/freescale/fec_main.c         | 11 ++++++++---
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/net/fsl-fec.txt b/Documentation/devicetree/bindings/net/fsl-fec.txt
index ff8b0f211aa1..26c492a2e0e1 100644
--- a/Documentation/devicetree/bindings/net/fsl-fec.txt
+++ b/Documentation/devicetree/bindings/net/fsl-fec.txt
@@ -82,6 +82,7 @@ ethernet@83fec000 {
 	phy-supply = <&reg_fec_supply>;
 	phy-handle = <&ethphy>;
 	mdio {
+	        clock-frequency = <5000000>;
 		ethphy: ethernet-phy@6 {
 			compatible = "ethernet-phy-ieee802.3-c22";
 			reg = <6>;
diff --git a/Documentation/devicetree/bindings/net/mdio.yaml b/Documentation/devicetree/bindings/net/mdio.yaml
index 50c3397a82bc..bcd457c54cd7 100644
--- a/Documentation/devicetree/bindings/net/mdio.yaml
+++ b/Documentation/devicetree/bindings/net/mdio.yaml
@@ -39,6 +39,10 @@ properties:
       and must therefore be appropriately determined based on all PHY
       requirements (maximum value of all per-PHY RESET pulse widths).
 
+  clock-frequency:
+    description:
+      Desired MDIO bus clock frequency in Hz.
+
 patternProperties:
   "^ethernet-phy@[0-9a-f]+$":
     type: object
diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index 6530829632b1..28ef0abfa660 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -2067,6 +2067,7 @@ static int fec_enet_mii_init(struct platform_device *pdev)
 	struct device_node *node;
 	int err = -ENXIO;
 	u32 mii_speed, holdtime;
+	u32 bus_freq;
 
 	/*
 	 * The i.MX28 dual fec interfaces are not equal.
@@ -2094,15 +2095,20 @@ static int fec_enet_mii_init(struct platform_device *pdev)
 		return -ENOENT;
 	}
 
+	bus_freq = 2500000; /* 2.5MHz by default */
+	node = of_get_child_by_name(pdev->dev.of_node, "mdio");
+	if (node)
+		of_property_read_u32(node, "clock-frequency", &bus_freq);
+
 	/*
-	 * Set MII speed to 2.5 MHz (= clk_get_rate() / 2 * phy_speed)
+	 * Set MII speed (= clk_get_rate() / 2 * phy_speed)
 	 *
 	 * The formula for FEC MDC is 'ref_freq / (MII_SPEED x 2)' while
 	 * for ENET-MAC is 'ref_freq / ((MII_SPEED + 1) x 2)'.  The i.MX28
 	 * Reference Manual has an error on this, and gets fixed on i.MX6Q
 	 * document.
 	 */
-	mii_speed = DIV_ROUND_UP(clk_get_rate(fep->clk_ipg), 5000000);
+	mii_speed = DIV_ROUND_UP(clk_get_rate(fep->clk_ipg), bus_freq * 2);
 	if (fep->quirks & FEC_QUIRK_ENET_MAC)
 		mii_speed--;
 	if (mii_speed > 63) {
@@ -2148,7 +2154,6 @@ static int fec_enet_mii_init(struct platform_device *pdev)
 	fep->mii_bus->priv = fep;
 	fep->mii_bus->parent = &pdev->dev;
 
-	node = of_get_child_by_name(pdev->dev.of_node, "mdio");
 	err = of_mdiobus_register(fep->mii_bus, node);
 	of_node_put(node);
 	if (err)
-- 
2.26.1