pwm-vt8500.c revision a245ccebb4aad9fae60597d5cbad158c0de4483e 
1/*
2 * arch/arm/mach-vt8500/pwm.c
3 *
4 *  Copyright (C) 2010 Alexey Charkov <alchark@gmail.com>
5 *
6 * This software is licensed under the terms of the GNU General Public
7 * License version 2, as published by the Free Software Foundation, and
8 * may be copied, distributed, and modified under those terms.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13 * GNU General Public License for more details.
14 */
15
16#include <linux/module.h>
17#include <linux/kernel.h>
18#include <linux/platform_device.h>
19#include <linux/slab.h>
20#include <linux/err.h>
21#include <linux/io.h>
22#include <linux/pwm.h>
23#include <linux/delay.h>
24
25#include <asm/div64.h>
26
27#define VT8500_NR_PWMS 4
28
29struct vt8500_chip {
30	struct pwm_chip chip;
31	void __iomem *base;
32};
33
34#define to_vt8500_chip(chip)	container_of(chip, struct vt8500_chip, chip)
35
36#define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t)
37static inline void pwm_busy_wait(void __iomem *reg, u8 bitmask)
38{
39	int loops = msecs_to_loops(10);
40	while ((readb(reg) & bitmask) && --loops)
41		cpu_relax();
42
43	if (unlikely(!loops))
44		pr_warning("Waiting for status bits 0x%x to clear timed out\n",
45			   bitmask);
46}
47
48static int vt8500_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
49		int duty_ns, int period_ns)
50{
51	struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
52	unsigned long long c;
53	unsigned long period_cycles, prescale, pv, dc;
54
55	c = 25000000/2; /* wild guess --- need to implement clocks */
56	c = c * period_ns;
57	do_div(c, 1000000000);
58	period_cycles = c;
59
60	if (period_cycles < 1)
61		period_cycles = 1;
62	prescale = (period_cycles - 1) / 4096;
63	pv = period_cycles / (prescale + 1) - 1;
64	if (pv > 4095)
65		pv = 4095;
66
67	if (prescale > 1023)
68		return -EINVAL;
69
70	c = (unsigned long long)pv * duty_ns;
71	do_div(c, period_ns);
72	dc = c;
73
74	pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 1));
75	writel(prescale, vt8500->base + 0x4 + (pwm->hwpwm << 4));
76
77	pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 2));
78	writel(pv, vt8500->base + 0x8 + (pwm->hwpwm << 4));
79
80	pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 3));
81	writel(dc, vt8500->base + 0xc + (pwm->hwpwm << 4));
82
83	return 0;
84}
85
86static int vt8500_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
87{
88	struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
89
90	pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 0));
91	writel(5, vt8500->base + (pwm->hwpwm << 4));
92	return 0;
93}
94
95static void vt8500_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
96{
97	struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
98
99	pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 0));
100	writel(0, vt8500->base + (pwm->hwpwm << 4));
101}
102
103static struct pwm_ops vt8500_pwm_ops = {
104	.enable = vt8500_pwm_enable,
105	.disable = vt8500_pwm_disable,
106	.config = vt8500_pwm_config,
107	.owner = THIS_MODULE,
108};
109
110static int __devinit pwm_probe(struct platform_device *pdev)
111{
112	struct vt8500_chip *chip;
113	struct resource *r;
114	int ret;
115
116	chip = kzalloc(sizeof(*chip), GFP_KERNEL);
117	if (chip == NULL) {
118		dev_err(&pdev->dev, "failed to allocate memory\n");
119		return -ENOMEM;
120	}
121
122	chip->chip.dev = &pdev->dev;
123	chip->chip.ops = &vt8500_pwm_ops;
124	chip->chip.base = -1;
125	chip->chip.npwm = VT8500_NR_PWMS;
126
127	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
128	if (r == NULL) {
129		dev_err(&pdev->dev, "no memory resource defined\n");
130		ret = -ENODEV;
131		goto err_free;
132	}
133
134	r = request_mem_region(r->start, resource_size(r), pdev->name);
135	if (r == NULL) {
136		dev_err(&pdev->dev, "failed to request memory resource\n");
137		ret = -EBUSY;
138		goto err_free;
139	}
140
141	chip->base = ioremap(r->start, resource_size(r));
142	if (chip->base == NULL) {
143		dev_err(&pdev->dev, "failed to ioremap() registers\n");
144		ret = -ENODEV;
145		goto err_free_mem;
146	}
147
148	ret = pwmchip_add(&chip->chip);
149	if (ret < 0)
150		goto err_unmap;
151
152	platform_set_drvdata(pdev, chip);
153	return ret;
154
155err_unmap:
156	iounmap(chip->base);
157err_free_mem:
158	release_mem_region(r->start, resource_size(r));
159err_free:
160	kfree(chip);
161	return ret;
162}
163
164static int __devexit pwm_remove(struct platform_device *pdev)
165{
166	struct vt8500_chip *chip;
167	struct resource *r;
168	int err;
169
170	chip = platform_get_drvdata(pdev);
171	if (chip == NULL)
172		return -ENODEV;
173
174	err = pwmchip_remove(&chip->chip);
175	if (err < 0)
176		return err;
177
178	iounmap(chip->base);
179
180	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
181	release_mem_region(r->start, resource_size(r));
182
183	kfree(chip);
184	return 0;
185}
186
187static struct platform_driver pwm_driver = {
188	.driver		= {
189		.name	= "vt8500-pwm",
190		.owner	= THIS_MODULE,
191	},
192	.probe		= pwm_probe,
193	.remove		= __devexit_p(pwm_remove),
194};
195
196static int __init pwm_init(void)
197{
198	return platform_driver_register(&pwm_driver);
199}
200arch_initcall(pwm_init);
201
202static void __exit pwm_exit(void)
203{
204	platform_driver_unregister(&pwm_driver);
205}
206module_exit(pwm_exit);
207
208MODULE_LICENSE("GPL");
209