can: mscan: improve clock API use

the .get_clock() callback is run from probe() and might allocate
resources, introduce a .put_clock() callback that is run from remove()
to undo any allocation activities

prepare and enable the clocks in open(), disable and unprepare the
clocks in close() if clocks were acquired during probe(), to not assume
knowledge about which activities are done in probe() and remove()

use devm_get_clk() to lookup the SYS and REF clocks, to have the clocks
put upon device shutdown

store pointers to data structures upon successful allocation already
instead of deferral until complete setup, such that subroutines in the
setup sequence may access those data structures as well to track their
resource acquisition

since clock allocation remains optional, the release callback as well as
the enable/disable calls in open/close are optional as well

Cc: linux-can@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Gerhard Sittig <gsi@denx.de>
Signed-off-by: Anatolij Gustschin <agust@denx.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/mscan/mpc5xxx_can.c

diff --git a/drivers/net/can/mscan/mpc5xxx_can.c b/drivers/net/can/mscan/mpc5xxx_can.c
index bc422ba..e59b3a3 100644
--- a/drivers/net/can/mscan/mpc5xxx_can.c
+++ b/drivers/net/can/mscan/mpc5xxx_can.c
@@ -40,6 +40,7 @@
 	unsigned int type;
 	u32 (*get_clock)(struct platform_device *ofdev, const char *clock_name,
 			 int *mscan_clksrc);
+	void (*put_clock)(struct platform_device *ofdev);
 };
 
 #ifdef CONFIG_PPC_MPC52xx
@@ -180,7 +181,7 @@
 			clockdiv = 1;
 
 		if (!clock_name || !strcmp(clock_name, "sys")) {
-			sys_clk = clk_get(&ofdev->dev, "sys_clk");
+			sys_clk = devm_clk_get(&ofdev->dev, "sys_clk");
 			if (IS_ERR(sys_clk)) {
 				dev_err(&ofdev->dev, "couldn't get sys_clk\n");
 				goto exit_unmap;
@@ -203,7 +204,7 @@
 		}
 
 		if (clocksrc < 0) {
-			ref_clk = clk_get(&ofdev->dev, "ref_clk");
+			ref_clk = devm_clk_get(&ofdev->dev, "ref_clk");
 			if (IS_ERR(ref_clk)) {
 				dev_err(&ofdev->dev, "couldn't get ref_clk\n");
 				goto exit_unmap;
@@ -280,6 +281,8 @@
 	dev = alloc_mscandev();
 	if (!dev)
 		goto exit_dispose_irq;
+	platform_set_drvdata(ofdev, dev);
+	SET_NETDEV_DEV(dev, &ofdev->dev);
 
 	priv = netdev_priv(dev);
 	priv->reg_base = base;
@@ -296,8 +299,6 @@
 		goto exit_free_mscan;
 	}
 
-	SET_NETDEV_DEV(dev, &ofdev->dev);
-
 	err = register_mscandev(dev, mscan_clksrc);
 	if (err) {
 		dev_err(&ofdev->dev, "registering %s failed (err=%d)\n",
@@ -305,8 +306,6 @@
 		goto exit_free_mscan;
 	}
 
-	platform_set_drvdata(ofdev, dev);
-
 	dev_info(&ofdev->dev, "MSCAN at 0x%p, irq %d, clock %d Hz\n",
 		 priv->reg_base, dev->irq, priv->can.clock.freq);
 
@@ -324,10 +323,17 @@
 
 static int mpc5xxx_can_remove(struct platform_device *ofdev)
 {
+	const struct of_device_id *match;
+	const struct mpc5xxx_can_data *data;
 	struct net_device *dev = platform_get_drvdata(ofdev);
 	struct mscan_priv *priv = netdev_priv(dev);
 
+	match = of_match_device(mpc5xxx_can_table, &ofdev->dev);
+	data = match ? match->data : NULL;
+
 	unregister_mscandev(dev);
+	if (data && data->put_clock)
+		data->put_clock(ofdev);
 	iounmap(priv->reg_base);
 	irq_dispose_mapping(dev->irq);
 	free_candev(dev);