pwm: vt8500: Update vt8500 PWM driver support

This patch updates pwm-vt8500.c to support devicetree probing and
make use of the common clock subsystem.

A binding document describing the PWM controller found on
arch-vt8500 is also included.
Signed-off-by: Tony Prisk <linux@prisktech.co.nz>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>

Documentation/devicetree/bindings/pwm/vt8500-pwm.txt

+VIA/Wondermedia VT8500/WM8xxx series SoC PWM controller
+
+Required properties:
+- compatible: should be "via,vt8500-pwm"
+- reg: physical base address and length of the controller's registers
+- #pwm-cells: should be 2.  The first cell specifies the per-chip index
+  of the PWM to use and the second cell is the period in nanoseconds.
+- clocks: phandle to the PWM source clock
+
+Example:
+
+pwm1: pwm@d8220000 {
+	#pwm-cells = <2>;
+	compatible = "via,vt8500-pwm";
+	reg = <0xd8220000 0x1000>;
+	clocks = <&clkpwm>;
+};

drivers/pwm/pwm-vt8500.c

 /*
  * drivers/pwm/pwm-vt8500.c
  *
+ * Copyright (C) 2012 Tony Prisk <linux@prisktech.co.nz>
  * Copyright (C) 2010 Alexey Charkov <alchark@gmail.com>
  *
  * This software is licensed under the terms of the GNU General Public
@@ -21,14 +22,24 @@
 #include <linux/io.h>
 #include <linux/pwm.h>
 #include <linux/delay.h>
+#include <linux/clk.h>
 
 #include <asm/div64.h>
 
-#define VT8500_NR_PWMS 4
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/of_address.h>
+
+/*
+ * SoC architecture allocates register space for 4 PWMs but only
+ * 2 are currently implemented.
+ */
+#define VT8500_NR_PWMS	2
 
 struct vt8500_chip {
 	struct pwm_chip chip;
 	void __iomem *base;
+	struct clk *clk;
 };
 
 #define to_vt8500_chip(chip)	container_of(chip, struct vt8500_chip, chip)
@@ -52,7 +63,7 @@ static int vt8500_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 	unsigned long long c;
 	unsigned long period_cycles, prescale, pv, dc;
 
-	c = 25000000/2; /* wild guess --- need to implement clocks */
+	c = clk_get_rate(vt8500->clk);
 	c = c * period_ns;
 	do_div(c, 1000000000);
 	period_cycles = c;
@@ -85,8 +96,15 @@ static int vt8500_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 
 static int vt8500_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
 {
+	int err;
 	struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
 
+	err = clk_enable(vt8500->clk);
+	if (err < 0)
+		dev_err(chip->dev, "failed to enable clock\n");
+		return err;
+	};
+
 	pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 0));
 	writel(5, vt8500->base + (pwm->hwpwm << 4));
 	return 0;
@@ -98,6 +116,8 @@ static void vt8500_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 
 	pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 0));
 	writel(0, vt8500->base + (pwm->hwpwm << 4));
+
+	clk_disable(vt8500->clk);
 }
 
 static struct pwm_ops vt8500_pwm_ops = {
@@ -107,12 +127,24 @@ static struct pwm_ops vt8500_pwm_ops = {
 	.owner = THIS_MODULE,
 };
 
-static int __devinit pwm_probe(struct platform_device *pdev)
+static const struct of_device_id vt8500_pwm_dt_ids[] = {
+	{ .compatible = "via,vt8500-pwm", },
+	{ /* Sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, vt8500_pwm_dt_ids);
+
+static int vt8500_pwm_probe(struct platform_device *pdev)
 {
 	struct vt8500_chip *chip;
 	struct resource *r;
+	struct device_node *np = pdev->dev.of_node;
 	int ret;
 
+	if (!np) {
+		dev_err(&pdev->dev, "invalid devicetree node\n");
+		return -EINVAL;
+	}
+
 	chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
 	if (chip == NULL) {
 		dev_err(&pdev->dev, "failed to allocate memory\n");
@@ -124,6 +156,12 @@ static int __devinit pwm_probe(struct platform_device *pdev)
 	chip->chip.base = -1;
 	chip->chip.npwm = VT8500_NR_PWMS;
 
+	chip->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(chip->clk)) {
+		dev_err(&pdev->dev, "clock source not specified\n");
+		return PTR_ERR(chip->clk);
+	}
+
 	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	if (r == NULL) {
 		dev_err(&pdev->dev, "no memory resource defined\n");
@@ -131,18 +169,26 @@ static int __devinit pwm_probe(struct platform_device *pdev)
 	}
 
 	chip->base = devm_request_and_ioremap(&pdev->dev, r);
-	if (chip->base == NULL)
+	if (!chip->base)
 		return -EADDRNOTAVAIL;
 
+	ret = clk_prepare(chip->clk);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "failed to prepare clock\n");
+		return ret;
+	}
+
 	ret = pwmchip_add(&chip->chip);
-	if (ret < 0)
+	if (ret < 0) {
+		dev_err(&pdev->dev, "failed to add PWM chip\n");
 		return ret;
+	}
 
 	platform_set_drvdata(pdev, chip);
 	return ret;
 }
 
-static int __devexit pwm_remove(struct platform_device *pdev)
+static int vt8500_pwm_remove(struct platform_device *pdev)
 {
 	struct vt8500_chip *chip;
 
@@ -150,28 +196,22 @@ static int __devexit pwm_remove(struct platform_device *pdev)
 	if (chip == NULL)
 		return -ENODEV;
 
+	clk_unprepare(chip->clk);
+
 	return pwmchip_remove(&chip->chip);
 }
 
-static struct platform_driver pwm_driver = {
+static struct platform_driver vt8500_pwm_driver = {
+	.probe		= vt8500_pwm_probe,
+	.remove		= vt8500_pwm_remove,
 	.driver		= {
 		.name	= "vt8500-pwm",
 		.owner	= THIS_MODULE,
+		.of_match_table = vt8500_pwm_dt_ids,
 	},
-	.probe		= pwm_probe,
-	.remove		= __devexit_p(pwm_remove),
 };
+module_platform_driver(vt8500_pwm_driver);
 
-static int __init pwm_init(void)
-{
-	return platform_driver_register(&pwm_driver);
-}
-arch_initcall(pwm_init);
-
-static void __exit pwm_exit(void)
-{
-	platform_driver_unregister(&pwm_driver);
-}
-module_exit(pwm_exit);
-
-MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("VT8500 PWM Driver");
+MODULE_AUTHOR("Tony Prisk <linux@prisktech.co.nz>");
+MODULE_LICENSE("GPL v2");