xref: /linux/drivers/pwm/pwm-vt8500.c (revision 4413e16d9d21673bb5048a2e542f1aaa00015c2e)
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 
29 struct 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)
37 static 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 
48 static 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 
86 static 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 
95 static 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 
103 static 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 
110 static 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 
145 static 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 
156 static 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 
165 static int __init pwm_init(void)
166 {
167 	return platform_driver_register(&pwm_driver);
168 }
169 arch_initcall(pwm_init);
170 
171 static void __exit pwm_exit(void)
172 {
173 	platform_driver_unregister(&pwm_driver);
174 }
175 module_exit(pwm_exit);
176 
177 MODULE_LICENSE("GPL");
178