misc: aspeed-lpc: Request and enable LPC clock

The LPC device needs to ensure it's clock is enabled before it can do
anything.

In the past the clock was enabled and left running by u-boot, however
Linux now has an upstream clock driver that disables unused clocks.

Tested-by: Lei YU <mine260309@gmail.com>
Reviewed-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/aspeed-lpc-ctrl.c

@@ -7,6 +7,7 @@
  * 2 of the License, or (at your option) any later version.
  */
 
+#include <linux/clk.h>
 #include <linux/mfd/syscon.h>
 #include <linux/miscdevice.h>
 #include <linux/mm.h>
@@ -26,6 +27,7 @@
 struct aspeed_lpc_ctrl {
 	struct miscdevice	miscdev;
 	struct regmap		*regmap;
+	struct clk		*clk;
 	phys_addr_t		mem_base;
 	resource_size_t		mem_size;
 	u32		pnor_size;
@@ -221,16 +223,33 @@ static int aspeed_lpc_ctrl_probe(struct platform_device *pdev)
 		return -ENODEV;
 	}
 
+	lpc_ctrl->clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(lpc_ctrl->clk)) {
+		dev_err(dev, "couldn't get clock\n");
+		return PTR_ERR(lpc_ctrl->clk);
+	}
+	rc = clk_prepare_enable(lpc_ctrl->clk);
+	if (rc) {
+		dev_err(dev, "couldn't enable clock\n");
+		return rc;
+	}
+
 	lpc_ctrl->miscdev.minor = MISC_DYNAMIC_MINOR;
 	lpc_ctrl->miscdev.name = DEVICE_NAME;
 	lpc_ctrl->miscdev.fops = &aspeed_lpc_ctrl_fops;
 	lpc_ctrl->miscdev.parent = dev;
 	rc = misc_register(&lpc_ctrl->miscdev);
-	if (rc)
+	if (rc) {
 		dev_err(dev, "Unable to register device\n");
-	else
-		dev_info(dev, "Loaded at %pr\n", &resm);
+		goto err;
+	}
+
+	dev_info(dev, "Loaded at %pr\n", &resm);
+
+	return 0;
 
+err:
+	clk_disable_unprepare(lpc_ctrl->clk);
 	return rc;
 }
 
@@ -239,6 +258,7 @@ static int aspeed_lpc_ctrl_remove(struct platform_device *pdev)
 	struct aspeed_lpc_ctrl *lpc_ctrl = dev_get_drvdata(&pdev->dev);
 
 	misc_deregister(&lpc_ctrl->miscdev);
+	clk_disable_unprepare(lpc_ctrl->clk);
 
 	return 0;
 }