Root/drivers/pwm/pwm-vt8500.c

1/*
2 * drivers/pwm/pwm-vt8500.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_warn("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 = devm_kzalloc(&pdev->dev, 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        return -ENODEV;
131    }
132
133    chip->base = devm_request_and_ioremap(&pdev->dev, r);
134    if (chip->base == NULL)
135        return -EADDRNOTAVAIL;
136
137    ret = pwmchip_add(&chip->chip);
138    if (ret < 0)
139        return ret;
140
141    platform_set_drvdata(pdev, chip);
142    return ret;
143}
144
145static int __devexit pwm_remove(struct platform_device *pdev)
146{
147    struct vt8500_chip *chip;
148
149    chip = platform_get_drvdata(pdev);
150    if (chip == NULL)
151        return -ENODEV;
152
153    return pwmchip_remove(&chip->chip);
154}
155
156static struct platform_driver pwm_driver = {
157    .driver = {
158        .name = "vt8500-pwm",
159        .owner = THIS_MODULE,
160    },
161    .probe = pwm_probe,
162    .remove = __devexit_p(pwm_remove),
163};
164
165static int __init pwm_init(void)
166{
167    return platform_driver_register(&pwm_driver);
168}
169arch_initcall(pwm_init);
170
171static void __exit pwm_exit(void)
172{
173    platform_driver_unregister(&pwm_driver);
174}
175module_exit(pwm_exit);
176
177MODULE_LICENSE("GPL");
178

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