net: smsc911x: Make Runtime PM handling more fine-grained

Currently the smsc911x driver has mininal power management: during
driver probe, the device is powered up, and during driver remove, it is
powered down.

Improve power management by making it more fine-grained:
  1. Power the device down when driver probe is finished,
  2. Power the device (down) when it is opened (closed),
  3. Make sure the device is powered during PHY access.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20210118150857.796943-1-geert+renesas@glider.beSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/smsc/smsc911x.c

@@ -557,6 +557,7 @@ static int smsc911x_mii_read(struct mii_bus *bus, int phyaddr, int regidx)
 	unsigned int addr;
 	int i, reg;
 
+	pm_runtime_get_sync(bus->parent);
 	spin_lock_irqsave(&pdata->mac_lock, flags);
 
 	/* Confirm MII not busy */
@@ -582,6 +583,7 @@ static int smsc911x_mii_read(struct mii_bus *bus, int phyaddr, int regidx)
 
 out:
 	spin_unlock_irqrestore(&pdata->mac_lock, flags);
+	pm_runtime_put(bus->parent);
 	return reg;
 }
 
@@ -594,6 +596,7 @@ static int smsc911x_mii_write(struct mii_bus *bus, int phyaddr, int regidx,
 	unsigned int addr;
 	int i, reg;
 
+	pm_runtime_get_sync(bus->parent);
 	spin_lock_irqsave(&pdata->mac_lock, flags);
 
 	/* Confirm MII not busy */
@@ -623,6 +626,7 @@ static int smsc911x_mii_write(struct mii_bus *bus, int phyaddr, int regidx,
 
 out:
 	spin_unlock_irqrestore(&pdata->mac_lock, flags);
+	pm_runtime_put(bus->parent);
 	return reg;
 }
 
@@ -1589,6 +1593,8 @@ static int smsc911x_open(struct net_device *dev)
 	int retval;
 	int irq_flags;
 
+	pm_runtime_get_sync(dev->dev.parent);
+
 	/* find and start the given phy */
 	if (!dev->phydev) {
 		retval = smsc911x_mii_probe(dev);
@@ -1735,6 +1741,7 @@ static int smsc911x_open(struct net_device *dev)
 	phy_disconnect(dev->phydev);
 	dev->phydev = NULL;
 out:
+	pm_runtime_put(dev->dev.parent);
 	return retval;
 }
 
@@ -1766,6 +1773,7 @@ static int smsc911x_stop(struct net_device *dev)
 		dev->phydev = NULL;
 	}
 	netif_carrier_off(dev);
+	pm_runtime_put(dev->dev.parent);
 
 	SMSC_TRACE(pdata, ifdown, "Interface stopped");
 	return 0;
@@ -2334,7 +2342,6 @@ static int smsc911x_drv_remove(struct platform_device *pdev)
 
 	free_netdev(dev);
 
-	pm_runtime_put(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
 
 	return 0;
@@ -2540,6 +2547,7 @@ static int smsc911x_drv_probe(struct platform_device *pdev)
 	}
 
 	spin_unlock_irq(&pdata->mac_lock);
+	pm_runtime_put(&pdev->dev);
 
 	netdev_info(dev, "MAC Address: %pM\n", dev->dev_addr);