net: mdio: Add the reset function for IPQ MDIO driver

1. configure the MDIO clock source frequency.
2. the LDO resource is needed to configure the ethernet LDO available
for CMN_PLL.
Signed-off-by: Luo Jie <luoj@codeaurora.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/mdio/Kconfig

@@ -169,6 +169,7 @@ config MDIO_OCTEON
 config MDIO_IPQ4019
 	tristate "Qualcomm IPQ4019 MDIO interface support"
 	depends on HAS_IOMEM && OF_MDIO
+	depends on COMMON_CLK
 	help
 	  This driver supports the MDIO interface found in Qualcomm
 	  IPQ40xx series Soc-s.

drivers/net/mdio/mdio-ipq4019.c

@@ -11,6 +11,7 @@
 #include <linux/of_mdio.h>
 #include <linux/phy.h>
 #include <linux/platform_device.h>
+#include <linux/clk.h>
 
 #define MDIO_MODE_REG				0x40
 #define MDIO_ADDR_REG				0x44
@@ -31,8 +32,15 @@
 #define IPQ4019_MDIO_TIMEOUT	10000
 #define IPQ4019_MDIO_SLEEP		10
 
+/* MDIO clock source frequency is fixed to 100M */
+#define IPQ_MDIO_CLK_RATE	100000000
+
+#define IPQ_PHY_SET_DELAY_US	100000
+
 struct ipq4019_mdio_data {
 	void __iomem	*membase;
+	void __iomem *eth_ldo_rdy;
+	struct clk *mdio_clk;
 };
 
 static int ipq4019_mdio_wait_busy(struct mii_bus *bus)
@@ -171,10 +179,35 @@ static int ipq4019_mdio_write(struct mii_bus *bus, int mii_id, int regnum,
 	return 0;
 }
 
+static int ipq_mdio_reset(struct mii_bus *bus)
+{
+	struct ipq4019_mdio_data *priv = bus->priv;
+	u32 val;
+	int ret;
+
+	/* To indicate CMN_PLL that ethernet_ldo has been ready if platform resource 1
+	 * is specified in the device tree.
+	 */
+	if (priv->eth_ldo_rdy) {
+		val = readl(priv->eth_ldo_rdy);
+		val |= BIT(0);
+		writel(val, priv->eth_ldo_rdy);
+		fsleep(IPQ_PHY_SET_DELAY_US);
+	}
+
+	/* Configure MDIO clock source frequency if clock is specified in the device tree */
+	ret = clk_set_rate(priv->mdio_clk, IPQ_MDIO_CLK_RATE);
+	if (ret)
+		return ret;
+
+	return clk_prepare_enable(priv->mdio_clk);
+}
+
 static int ipq4019_mdio_probe(struct platform_device *pdev)
 {
 	struct ipq4019_mdio_data *priv;
 	struct mii_bus *bus;
+	struct resource *res;
 	int ret;
 
 	bus = devm_mdiobus_alloc_size(&pdev->dev, sizeof(*priv));
@@ -187,9 +220,19 @@ static int ipq4019_mdio_probe(struct platform_device *pdev)
 	if (IS_ERR(priv->membase))
 		return PTR_ERR(priv->membase);
 
+	priv->mdio_clk = devm_clk_get_optional(&pdev->dev, "gcc_mdio_ahb_clk");
+	if (IS_ERR(priv->mdio_clk))
+		return PTR_ERR(priv->mdio_clk);
+
+	/* The platform resource is provided on the chipset IPQ5018 */
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+	if (res)
+		priv->eth_ldo_rdy = devm_ioremap_resource(&pdev->dev, res);
+
 	bus->name = "ipq4019_mdio";
 	bus->read = ipq4019_mdio_read;
 	bus->write = ipq4019_mdio_write;
+	bus->reset = ipq_mdio_reset;
 	bus->parent = &pdev->dev;
 	snprintf(bus->id, MII_BUS_ID_SIZE, "%s%d", pdev->name, pdev->id);