net: ethoc: set up MII management bus clock

MII management bus clock is derived from the MAC clock by dividing it by
MIIMODER register CLKDIV field value. This value may need to be set up
in case it is undefined or its default value is too high (and
communication with PHY is too slow) or too low (and communication with
PHY is impossible). The value of CLKDIV is not specified directly, but
is derived from the MAC clock for the default MII management bus frequency
of 2.5MHz. The MAC clock may be specified in the platform data, or in
the 'clocks' device tree attribute.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ethoc.c

@@ -13,6 +13,7 @@
 
 #include <linux/dma-mapping.h>
 #include <linux/etherdevice.h>
+#include <linux/clk.h>
 #include <linux/crc32.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
@@ -219,6 +220,7 @@ struct ethoc {
 
 	struct phy_device *phy;
 	struct mii_bus *mdio;
+	struct clk *clk;
 	s8 phy_id;
 };
 
@@ -1021,6 +1023,8 @@ static int ethoc_probe(struct platform_device *pdev)
 	int num_bd;
 	int ret = 0;
 	bool random_mac = false;
+	struct ethoc_platform_data *pdata = dev_get_platdata(&pdev->dev);
+	u32 eth_clkfreq = pdata ? pdata->eth_clkfreq : 0;
 
 	/* allocate networking device */
 	netdev = alloc_etherdev(sizeof(struct ethoc));
@@ -1135,8 +1139,7 @@ static int ethoc_probe(struct platform_device *pdev)
 	}
 
 	/* Allow the platform setup code to pass in a MAC address. */
-	if (dev_get_platdata(&pdev->dev)) {
-		struct ethoc_platform_data *pdata = dev_get_platdata(&pdev->dev);
+	if (pdata) {
 		memcpy(netdev->dev_addr, pdata->hwaddr, IFHWADDRLEN);
 		priv->phy_id = pdata->phy_id;
 	} else {
@@ -1174,6 +1177,27 @@ static int ethoc_probe(struct platform_device *pdev)
 	if (random_mac)
 		netdev->addr_assign_type = NET_ADDR_RANDOM;
 
+	/* Allow the platform setup code to adjust MII management bus clock. */
+	if (!eth_clkfreq) {
+		struct clk *clk = devm_clk_get(&pdev->dev, NULL);
+
+		if (!IS_ERR(clk)) {
+			priv->clk = clk;
+			clk_prepare_enable(clk);
+			eth_clkfreq = clk_get_rate(clk);
+		}
+	}
+	if (eth_clkfreq) {
+		u32 clkdiv = MIIMODER_CLKDIV(eth_clkfreq / 2500000 + 1);
+
+		if (!clkdiv)
+			clkdiv = 2;
+		dev_dbg(&pdev->dev, "setting MII clkdiv to %u\n", clkdiv);
+		ethoc_write(priv, MIIMODER,
+			    (ethoc_read(priv, MIIMODER) & MIIMODER_NOPRE) |
+			    clkdiv);
+	}
+
 	/* register MII bus */
 	priv->mdio = mdiobus_alloc();
 	if (!priv->mdio) {
@@ -1239,6 +1263,8 @@ free_mdio:
 	kfree(priv->mdio->irq);
 	mdiobus_free(priv->mdio);
 free:
+	if (priv->clk)
+		clk_disable_unprepare(priv->clk);
 	free_netdev(netdev);
 out:
 	return ret;
@@ -1263,6 +1289,8 @@ static int ethoc_remove(struct platform_device *pdev)
 			kfree(priv->mdio->irq);
 			mdiobus_free(priv->mdio);
 		}
+		if (priv->clk)
+			clk_disable_unprepare(priv->clk);
 		unregister_netdev(netdev);
 		free_netdev(netdev);
 	}

include/net/ethoc.h

@@ -16,6 +16,7 @@
 struct ethoc_platform_data {
 	u8 hwaddr[IFHWADDRLEN];
 	s8 phy_id;
+	u32 eth_clkfreq;
 };
 
 #endif /* !LINUX_NET_ETHOC_H */