net: mvmdio: enhance driver to support SMI error/done interrupts

This patch enhances the "mvmdio" to support a SMI error/done interrupt
line which can be used along with a wait queue instead of doing
busy-waiting on the registers. This is a feature which is available in
the mv643xx_eth SMI code and thus reduces again the gap between the two.

Signed-off-by: Florian Fainelli <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

Documentation/devicetree/bindings/net/marvell-orion-mdio.txt

···
 - compatible: "marvell,orion-mdio"
 - reg: address and length of the SMI register
 
+Optional properties:
+- interrupts: interrupt line number for the SMI error/done interrupt
+
 The child nodes of the MDIO driver are the individual PHY devices
 connected to this MDIO bus. They must have a "reg" property given the
 PHY address on the MDIO bus.

drivers/net/ethernet/marvell/mvmdio.c

···
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/phy.h>
+#include <linux/interrupt.h>
 #include <linux/platform_device.h>
 #include <linux/delay.h>
 #include <linux/io.h>
 #include <linux/of_mdio.h>
+#include <linux/sched.h>
+#include <linux/wait.h>
 
 #define MVMDIO_SMI_DATA_SHIFT              0
 #define MVMDIO_SMI_PHY_ADDR_SHIFT          16
···
 #define MVMDIO_SMI_WRITE_OPERATION         0
 #define MVMDIO_SMI_READ_VALID              BIT(27)
 #define MVMDIO_SMI_BUSY                    BIT(28)
+#define MVMDIO_ERR_INT_CAUSE		   0x007C
+#define  MVMDIO_ERR_INT_SMI_DONE	   0x00000010
+#define MVMDIO_ERR_INT_MASK		   0x0080
 
 struct orion_mdio_dev {
 	struct mutex lock;
 	void __iomem *regs;
+	/*
+	 * If we have access to the error interrupt pin (which is
+	 * somewhat misnamed as it not only reflects internal errors
+	 * but also reflects SMI completion), use that to wait for
+	 * SMI access completion instead of polling the SMI busy bit.
+	 */
+	int err_interrupt;
+	wait_queue_head_t smi_busy_wait;
 };
+
+static int orion_mdio_smi_is_done(struct orion_mdio_dev *dev)
+{
+	return !(readl(dev->regs) & MVMDIO_SMI_BUSY);
+}
 
 /* Wait for the SMI unit to be ready for another operation
  */
···
 {
 	struct orion_mdio_dev *dev = bus->priv;
 	int count;
-	u32 val;
 
-	count = 0;
-	while (1) {
-		val = readl(dev->regs);
-		if (!(val & MVMDIO_SMI_BUSY))
-			break;
+	if (dev->err_interrupt <= 0) {
+		count = 0;
+		while (1) {
+			if (orion_mdio_smi_is_done(dev))
+				break;
 
-		if (count > 100) {
-			dev_err(bus->parent, "Timeout: SMI busy for too long\n");
-			return -ETIMEDOUT;
+			if (count > 100) {
+				dev_err(bus->parent,
+					"Timeout: SMI busy for too long\n");
+				return -ETIMEDOUT;
+			}
+
+			udelay(10);
+			count++;
 		}
-
-		udelay(10);
-		count++;
+	} else {
+		if (!orion_mdio_smi_is_done(dev)) {
+			wait_event_timeout(dev->smi_busy_wait,
+				orion_mdio_smi_is_done(dev),
+				msecs_to_jiffies(100));
+			if (!orion_mdio_smi_is_done(dev))
+				return -ETIMEDOUT;
+		}
 	}
 
 	return 0;
···
 	return 0;
 }
 
+static irqreturn_t orion_mdio_err_irq(int irq, void *dev_id)
+{
+	struct orion_mdio_dev *dev = dev_id;
+
+	if (readl(dev->regs + MVMDIO_ERR_INT_CAUSE) &
+			MVMDIO_ERR_INT_SMI_DONE) {
+		writel(~MVMDIO_ERR_INT_SMI_DONE,
+				dev->regs + MVMDIO_ERR_INT_CAUSE);
+		wake_up(&dev->smi_busy_wait);
+		return IRQ_HANDLED;
+	}
+
+	return IRQ_NONE;
+}
+
 static int orion_mdio_probe(struct platform_device *pdev)
 {
 	struct resource *r;
···
 	dev->regs = devm_ioremap(&pdev->dev, r->start, resource_size(r));
 	if (!dev->regs) {
 		dev_err(&pdev->dev, "Unable to remap SMI register\n");
-		kfree(bus->irq);
-		mdiobus_free(bus);
-		return -ENODEV;
+		ret = -ENODEV;
+		goto out_mdio;
+	}
+
+	init_waitqueue_head(&dev->smi_busy_wait);
+
+	dev->err_interrupt = platform_get_irq(pdev, 0);
+	if (dev->err_interrupt != -ENXIO) {
+		ret = devm_request_irq(&pdev->dev, dev->err_interrupt,
+					orion_mdio_err_irq,
+					IRQF_SHARED, pdev->name, dev);
+		if (ret)
+			goto out_mdio;
+
+		writel(MVMDIO_ERR_INT_SMI_DONE,
+			dev->regs + MVMDIO_ERR_INT_MASK);
 	}
 
 	mutex_init(&dev->lock);
···
 		ret = mdiobus_register(bus);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "Cannot register MDIO bus (%d)\n", ret);
-		kfree(bus->irq);
-		mdiobus_free(bus);
-		return ret;
+		goto out_mdio;
 	}
 
 	platform_set_drvdata(pdev, bus);
 
 	return 0;
+
+out_mdio:
+	kfree(bus->irq);
+	mdiobus_free(bus);
+	return ret;
 }
 
 static int orion_mdio_remove(struct platform_device *pdev)
 {
 	struct mii_bus *bus = platform_get_drvdata(pdev);
+	struct orion_mdio_dev *dev = bus->priv;
+
+	writel(0, dev->regs + MVMDIO_ERR_INT_MASK);
 	mdiobus_unregister(bus);
 	kfree(bus->irq);
 	mdiobus_free(bus);