net: fec: Ensure clocks are enabled while using mdio bus

When a switch is attached to the mdio bus, the mdio bus can be used
while the interface is not open. If the IPG clock is not enabled, MDIO
reads/writes will simply time out.

Add support for runtime PM to control this clock. Enable/disable this
clock using runtime PM, with open()/close() and mdio read()/write()
function triggering runtime PM operations. Since PM is optional, the
IPG clock is enabled at probe and is no longer modified by
fec_enet_clk_enable(), thus if PM is not enabled in the kernel, it is
guaranteed the clock is running when MDIO operations are performed.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Cc: tyler.baker@linaro.org
Cc: fabio.estevam@freescale.com
Cc: shawn.guo@linaro.org
Tested-by: Fabio Estevam <fabio.estevam@freescale.com>
Tested-by: Tyler Baker <tyler.baker@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/fec_main.c

@@ -24,6 +24,7 @@
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/string.h>
+#include <linux/pm_runtime.h>
 #include <linux/ptrace.h>
 #include <linux/errno.h>
 #include <linux/ioport.h>
@@ -77,6 +78,7 @@ static void fec_enet_itr_coal_init(struct net_device *ndev);
 #define FEC_ENET_RAEM_V	0x8
 #define FEC_ENET_RAFL_V	0x8
 #define FEC_ENET_OPD_V	0xFFF0
+#define FEC_MDIO_PM_TIMEOUT  100 /* ms */
 
 static struct platform_device_id fec_devtype[] = {
 	{
@@ -1767,7 +1769,13 @@ static void fec_enet_adjust_link(struct net_device *ndev)
 static int fec_enet_mdio_read(struct mii_bus *bus, int mii_id, int regnum)
 {
 	struct fec_enet_private *fep = bus->priv;
+	struct device *dev = &fep->pdev->dev;
 	unsigned long time_left;
+	int ret = 0;
+
+	ret = pm_runtime_get_sync(dev);
+	if (IS_ERR_VALUE(ret))
+		return ret;
 
 	fep->mii_timeout = 0;
 	init_completion(&fep->mdio_done);
@@ -1783,18 +1791,30 @@ static int fec_enet_mdio_read(struct mii_bus *bus, int mii_id, int regnum)
 	if (time_left == 0) {
 		fep->mii_timeout = 1;
 		netdev_err(fep->netdev, "MDIO read timeout\n");
-		return -ETIMEDOUT;
+		ret = -ETIMEDOUT;
+		goto out;
 	}
 
-	/* return value */
-	return FEC_MMFR_DATA(readl(fep->hwp + FEC_MII_DATA));
+	ret = FEC_MMFR_DATA(readl(fep->hwp + FEC_MII_DATA));
+
+out:
+	pm_runtime_mark_last_busy(dev);
+	pm_runtime_put_autosuspend(dev);
+
+	return ret;
 }
 
 static int fec_enet_mdio_write(struct mii_bus *bus, int mii_id, int regnum,
 			   u16 value)
 {
 	struct fec_enet_private *fep = bus->priv;
+	struct device *dev = &fep->pdev->dev;
 	unsigned long time_left;
+	int ret = 0;
+
+	ret = pm_runtime_get_sync(dev);
+	if (IS_ERR_VALUE(ret))
+		return ret;
 
 	fep->mii_timeout = 0;
 	init_completion(&fep->mdio_done);
@@ -1811,10 +1831,13 @@ static int fec_enet_mdio_write(struct mii_bus *bus, int mii_id, int regnum,
 	if (time_left == 0) {
 		fep->mii_timeout = 1;
 		netdev_err(fep->netdev, "MDIO write timeout\n");
-		return -ETIMEDOUT;
+		ret  = -ETIMEDOUT;
 	}
 
-	return 0;
+	pm_runtime_mark_last_busy(dev);
+	pm_runtime_put_autosuspend(dev);
+
+	return ret;
 }
 
 static int fec_enet_clk_enable(struct net_device *ndev, bool enable)
@@ -1826,9 +1849,6 @@ static int fec_enet_clk_enable(struct net_device *ndev, bool enable)
 		ret = clk_prepare_enable(fep->clk_ahb);
 		if (ret)
 			return ret;
-		ret = clk_prepare_enable(fep->clk_ipg);
-		if (ret)
-			goto failed_clk_ipg;
 		if (fep->clk_enet_out) {
 			ret = clk_prepare_enable(fep->clk_enet_out);
 			if (ret)
@@ -1852,7 +1872,6 @@ static int fec_enet_clk_enable(struct net_device *ndev, bool enable)
 		}
 	} else {
 		clk_disable_unprepare(fep->clk_ahb);
-		clk_disable_unprepare(fep->clk_ipg);
 		if (fep->clk_enet_out)
 			clk_disable_unprepare(fep->clk_enet_out);
 		if (fep->clk_ptp) {
@@ -1874,8 +1893,6 @@ failed_clk_ptp:
 	if (fep->clk_enet_out)
 		clk_disable_unprepare(fep->clk_enet_out);
 failed_clk_enet_out:
-		clk_disable_unprepare(fep->clk_ipg);
-failed_clk_ipg:
 		clk_disable_unprepare(fep->clk_ahb);
 
 	return ret;
@@ -2847,10 +2864,14 @@ fec_enet_open(struct net_device *ndev)
 	struct fec_enet_private *fep = netdev_priv(ndev);
 	int ret;
 
+	ret = pm_runtime_get_sync(&fep->pdev->dev);
+	if (IS_ERR_VALUE(ret))
+		return ret;
+
 	pinctrl_pm_select_default_state(&fep->pdev->dev);
 	ret = fec_enet_clk_enable(ndev, true);
 	if (ret)
-		return ret;
+		goto clk_enable;
 
 	/* I should reset the ring buffers here, but I don't yet know
 	 * a simple way to do that.
@@ -2881,6 +2902,9 @@ err_enet_mii_probe:
 	fec_enet_free_buffers(ndev);
 err_enet_alloc:
 	fec_enet_clk_enable(ndev, false);
+clk_enable:
+	pm_runtime_mark_last_busy(&fep->pdev->dev);
+	pm_runtime_put_autosuspend(&fep->pdev->dev);
 	pinctrl_pm_select_sleep_state(&fep->pdev->dev);
 	return ret;
 }
@@ -2903,6 +2927,9 @@ fec_enet_close(struct net_device *ndev)
 
 	fec_enet_clk_enable(ndev, false);
 	pinctrl_pm_select_sleep_state(&fep->pdev->dev);
+	pm_runtime_mark_last_busy(&fep->pdev->dev);
+	pm_runtime_put_autosuspend(&fep->pdev->dev);
+
 	fec_enet_free_buffers(ndev);
 
 	return 0;
@@ -3388,6 +3415,10 @@ fec_probe(struct platform_device *pdev)
 	if (ret)
 		goto failed_clk;
 
+	ret = clk_prepare_enable(fep->clk_ipg);
+	if (ret)
+		goto failed_clk_ipg;
+
 	fep->reg_phy = devm_regulator_get(&pdev->dev, "phy");
 	if (!IS_ERR(fep->reg_phy)) {
 		ret = regulator_enable(fep->reg_phy);
@@ -3400,6 +3431,11 @@ fec_probe(struct platform_device *pdev)
 		fep->reg_phy = NULL;
 	}
 
+	pm_runtime_set_autosuspend_delay(&pdev->dev, FEC_MDIO_PM_TIMEOUT);
+	pm_runtime_use_autosuspend(&pdev->dev);
+	pm_runtime_set_active(&pdev->dev);
+	pm_runtime_enable(&pdev->dev);
+
 	fec_reset_phy(pdev);
 
 	if (fep->bufdesc_ex)
@@ -3447,6 +3483,10 @@ fec_probe(struct platform_device *pdev)
 
 	fep->rx_copybreak = COPYBREAK_DEFAULT;
 	INIT_WORK(&fep->tx_timeout_work, fec_enet_timeout_work);
+
+	pm_runtime_mark_last_busy(&pdev->dev);
+	pm_runtime_put_autosuspend(&pdev->dev);
+
 	return 0;
 
 failed_register:
@@ -3458,6 +3498,8 @@ failed_init:
 	if (fep->reg_phy)
 		regulator_disable(fep->reg_phy);
 failed_regulator:
+	clk_disable_unprepare(fep->clk_ipg);
+failed_clk_ipg:
 	fec_enet_clk_enable(ndev, false);
 failed_clk:
 failed_phy:
@@ -3567,7 +3609,28 @@ failed_clk:
 	return ret;
 }
 
-static SIMPLE_DEV_PM_OPS(fec_pm_ops, fec_suspend, fec_resume);
+static int __maybe_unused fec_runtime_suspend(struct device *dev)
+{
+	struct net_device *ndev = dev_get_drvdata(dev);
+	struct fec_enet_private *fep = netdev_priv(ndev);
+
+	clk_disable_unprepare(fep->clk_ipg);
+
+	return 0;
+}
+
+static int __maybe_unused fec_runtime_resume(struct device *dev)
+{
+	struct net_device *ndev = dev_get_drvdata(dev);
+	struct fec_enet_private *fep = netdev_priv(ndev);
+
+	return clk_prepare_enable(fep->clk_ipg);
+}
+
+static const struct dev_pm_ops fec_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(fec_suspend, fec_resume)
+	SET_RUNTIME_PM_OPS(fec_runtime_suspend, fec_runtime_resume, NULL)
+};
 
 static struct platform_driver fec_driver = {
 	.driver	= {