net: phy: mscc-miim: add support to set MDIO bus frequency

Until now, the MDIO bus will have the hardware default bus frequency.
Read the desired frequency of the bus from the device tree and configure
it.
Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/mdio/mdio-mscc-miim.c

@@ -7,6 +7,7 @@
  */
 
 #include <linux/bitops.h>
+#include <linux/clk.h>
 #include <linux/io.h>
 #include <linux/iopoll.h>
 #include <linux/kernel.h>
@@ -30,6 +31,8 @@
 #define		MSCC_MIIM_CMD_VLD		BIT(31)
 #define MSCC_MIIM_REG_DATA		0xC
 #define		MSCC_MIIM_DATA_ERROR		(BIT(16) | BIT(17))
+#define MSCC_MIIM_REG_CFG		0x10
+#define		MSCC_MIIM_CFG_PRESCALE_MASK	GENMASK(7, 0)
 
 #define MSCC_PHY_REG_PHY_CFG	0x0
 #define		PHY_CFG_PHY_ENA		(BIT(0) | BIT(1) | BIT(2) | BIT(3))
@@ -50,6 +53,8 @@ struct mscc_miim_dev {
 	int mii_status_offset;
 	struct regmap *phy_regs;
 	const struct mscc_miim_info *info;
+	struct clk *clk;
+	u32 bus_freq;
 };
 
 /* When high resolution timers aren't built-in: we can't use usleep_range() as
@@ -235,9 +240,32 @@ int mscc_miim_setup(struct device *dev, struct mii_bus **pbus, const char *name,
 }
 EXPORT_SYMBOL(mscc_miim_setup);
 
+static int mscc_miim_clk_set(struct mii_bus *bus)
+{
+	struct mscc_miim_dev *miim = bus->priv;
+	unsigned long rate;
+	u32 div;
+
+	/* Keep the current settings */
+	if (!miim->bus_freq)
+		return 0;
+
+	rate = clk_get_rate(miim->clk);
+
+	div = DIV_ROUND_UP(rate, 2 * miim->bus_freq) - 1;
+	if (div == 0 || div & ~MSCC_MIIM_CFG_PRESCALE_MASK) {
+		dev_err(&bus->dev, "Incorrect MDIO clock frequency\n");
+		return -EINVAL;
+	}
+
+	return regmap_update_bits(miim->regs, MSCC_MIIM_REG_CFG,
+				  MSCC_MIIM_CFG_PRESCALE_MASK, div);
+}
+
 static int mscc_miim_probe(struct platform_device *pdev)
 {
 	struct regmap *mii_regmap, *phy_regmap = NULL;
+	struct device_node *np = pdev->dev.of_node;
 	void __iomem *regs, *phy_regs;
 	struct mscc_miim_dev *miim;
 	struct resource *res;
@@ -288,21 +316,47 @@ static int mscc_miim_probe(struct platform_device *pdev)
 	if (!miim->info)
 		return -EINVAL;
 
-	ret = of_mdiobus_register(bus, pdev->dev.of_node);
+	miim->clk = devm_clk_get_optional(&pdev->dev, NULL);
+	if (IS_ERR(miim->clk))
+		return PTR_ERR(miim->clk);
+
+	of_property_read_u32(np, "clock-frequency", &miim->bus_freq);
+
+	if (miim->bus_freq && !miim->clk) {
+		dev_err(&pdev->dev,
+			"cannot use clock-frequency without a clock\n");
+		return -EINVAL;
+	}
+
+	ret = clk_prepare_enable(miim->clk);
+	if (ret)
+		return ret;
+
+	ret = mscc_miim_clk_set(bus);
+	if (ret)
+		goto out_disable_clk;
+
+	ret = of_mdiobus_register(bus, np);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "Cannot register MDIO bus (%d)\n", ret);
-		return ret;
+		goto out_disable_clk;
 	}
 
 	platform_set_drvdata(pdev, bus);
 
 	return 0;
+
+out_disable_clk:
+	clk_disable_unprepare(miim->clk);
+	return ret;
 }
 
 static int mscc_miim_remove(struct platform_device *pdev)
 {
 	struct mii_bus *bus = platform_get_drvdata(pdev);
+	struct mscc_miim_dev *miim = bus->priv;
 
+	clk_disable_unprepare(miim->clk);
 	mdiobus_unregister(bus);
 
 	return 0;