net: phy: restore mdio regs in the iproc mdio driver

BugLink: https://bugs.launchpad.net/bugs/1868628

commit 6f08e98d upstream.

The mii management register in iproc mdio block
does not have a retention register so it is lost on suspend.
Save and restore value of register while resuming from suspend.

Fixes: bb1a6197 ("net: phy: Initialize mdio clock at probe function")
Signed-off-by: Arun Parameswaran <arun.parameswaran@broadcom.com>
Signed-off-by: Scott Branden <scott.branden@broadcom.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

drivers/net/phy/mdio-bcm-iproc.c

@@ -188,6 +188,23 @@ static int iproc_mdio_remove(struct platform_device *pdev)
 	return 0;
 }
 
+#ifdef CONFIG_PM_SLEEP
+int iproc_mdio_resume(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct iproc_mdio_priv *priv = platform_get_drvdata(pdev);
+
+	/* restore the mii clock configuration */
+	iproc_mdio_config_clk(priv->base);
+
+	return 0;
+}
+
+static const struct dev_pm_ops iproc_mdio_pm_ops = {
+	.resume = iproc_mdio_resume
+};
+#endif /* CONFIG_PM_SLEEP */
+
 static const struct of_device_id iproc_mdio_of_match[] = {
 	{ .compatible = "brcm,iproc-mdio", },
 	{ /* sentinel */ },
@@ -198,6 +215,9 @@ static struct platform_driver iproc_mdio_driver = {
 	.driver = {
 		.name = "iproc-mdio",
 		.of_match_table = iproc_mdio_of_match,
+#ifdef CONFIG_PM_SLEEP
+		.pm = &iproc_mdio_pm_ops,
+#endif
 	},
 	.probe = iproc_mdio_probe,
 	.remove = iproc_mdio_remove,