pwm-vt8500.c revision 422470a8265fbb1d182c00ab2421f4b416ab2dba 
1/*
2 * drivers/pwm/pwm-vt8500.c
3 *
4 * Copyright (C) 2012 Tony Prisk <linux@prisktech.co.nz>
5 * Copyright (C) 2010 Alexey Charkov <alchark@gmail.com>
6 *
7 * This software is licensed under the terms of the GNU General Public
8 * License version 2, as published by the Free Software Foundation, and
9 * may be copied, distributed, and modified under those terms.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14 * GNU General Public License for more details.
15 */
16
17#include <linux/module.h>
18#include <linux/kernel.h>
19#include <linux/platform_device.h>
20#include <linux/slab.h>
21#include <linux/err.h>
22#include <linux/io.h>
23#include <linux/pwm.h>
24#include <linux/delay.h>
25#include <linux/clk.h>
26
27#include <asm/div64.h>
28
29#include <linux/of.h>
30#include <linux/of_device.h>
31#include <linux/of_address.h>
32
33/*
34 * SoC architecture allocates register space for 4 PWMs but only
35 * 2 are currently implemented.
36 */
37#define VT8500_NR_PWMS	2
38
39struct vt8500_chip {
40	struct pwm_chip chip;
41	void __iomem *base;
42	struct clk *clk;
43};
44
45#define to_vt8500_chip(chip)	container_of(chip, struct vt8500_chip, chip)
46
47#define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t)
48static inline void pwm_busy_wait(void __iomem *reg, u8 bitmask)
49{
50	int loops = msecs_to_loops(10);
51	while ((readb(reg) & bitmask) && --loops)
52		cpu_relax();
53
54	if (unlikely(!loops))
55		pr_warn("Waiting for status bits 0x%x to clear timed out\n",
56			   bitmask);
57}
58
59static int vt8500_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
60		int duty_ns, int period_ns)
61{
62	struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
63	unsigned long long c;
64	unsigned long period_cycles, prescale, pv, dc;
65	int err;
66
67	err = clk_enable(vt8500->clk);
68	if (err < 0) {
69		dev_err(chip->dev, "failed to enable clock\n");
70		return err;
71	}
72
73	c = clk_get_rate(vt8500->clk);
74	c = c * period_ns;
75	do_div(c, 1000000000);
76	period_cycles = c;
77
78	if (period_cycles < 1)
79		period_cycles = 1;
80	prescale = (period_cycles - 1) / 4096;
81	pv = period_cycles / (prescale + 1) - 1;
82	if (pv > 4095)
83		pv = 4095;
84
85	if (prescale > 1023) {
86		clk_disable(vt8500->clk);
87		return -EINVAL;
88	}
89
90	c = (unsigned long long)pv * duty_ns;
91	do_div(c, period_ns);
92	dc = c;
93
94	pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 1));
95	writel(prescale, vt8500->base + 0x4 + (pwm->hwpwm << 4));
96
97	pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 2));
98	writel(pv, vt8500->base + 0x8 + (pwm->hwpwm << 4));
99
100	pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 3));
101	writel(dc, vt8500->base + 0xc + (pwm->hwpwm << 4));
102
103	clk_disable(vt8500->clk);
104	return 0;
105}
106
107static int vt8500_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
108{
109	int err;
110	struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
111
112	err = clk_enable(vt8500->clk);
113	if (err < 0) {
114		dev_err(chip->dev, "failed to enable clock\n");
115		return err;
116	}
117
118	pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 0));
119	writel(5, vt8500->base + (pwm->hwpwm << 4));
120	return 0;
121}
122
123static void vt8500_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
124{
125	struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
126
127	pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 0));
128	writel(0, vt8500->base + (pwm->hwpwm << 4));
129
130	clk_disable(vt8500->clk);
131}
132
133static struct pwm_ops vt8500_pwm_ops = {
134	.enable = vt8500_pwm_enable,
135	.disable = vt8500_pwm_disable,
136	.config = vt8500_pwm_config,
137	.owner = THIS_MODULE,
138};
139
140static const struct of_device_id vt8500_pwm_dt_ids[] = {
141	{ .compatible = "via,vt8500-pwm", },
142	{ /* Sentinel */ }
143};
144MODULE_DEVICE_TABLE(of, vt8500_pwm_dt_ids);
145
146static int vt8500_pwm_probe(struct platform_device *pdev)
147{
148	struct vt8500_chip *chip;
149	struct resource *r;
150	struct device_node *np = pdev->dev.of_node;
151	int ret;
152
153	if (!np) {
154		dev_err(&pdev->dev, "invalid devicetree node\n");
155		return -EINVAL;
156	}
157
158	chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
159	if (chip == NULL) {
160		dev_err(&pdev->dev, "failed to allocate memory\n");
161		return -ENOMEM;
162	}
163
164	chip->chip.dev = &pdev->dev;
165	chip->chip.ops = &vt8500_pwm_ops;
166	chip->chip.base = -1;
167	chip->chip.npwm = VT8500_NR_PWMS;
168
169	chip->clk = devm_clk_get(&pdev->dev, NULL);
170	if (IS_ERR(chip->clk)) {
171		dev_err(&pdev->dev, "clock source not specified\n");
172		return PTR_ERR(chip->clk);
173	}
174
175	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
176	if (r == NULL) {
177		dev_err(&pdev->dev, "no memory resource defined\n");
178		return -ENODEV;
179	}
180
181	chip->base = devm_request_and_ioremap(&pdev->dev, r);
182	if (!chip->base)
183		return -EADDRNOTAVAIL;
184
185	ret = clk_prepare(chip->clk);
186	if (ret < 0) {
187		dev_err(&pdev->dev, "failed to prepare clock\n");
188		return ret;
189	}
190
191	ret = pwmchip_add(&chip->chip);
192	if (ret < 0) {
193		dev_err(&pdev->dev, "failed to add PWM chip\n");
194		return ret;
195	}
196
197	platform_set_drvdata(pdev, chip);
198	return ret;
199}
200
201static int vt8500_pwm_remove(struct platform_device *pdev)
202{
203	struct vt8500_chip *chip;
204
205	chip = platform_get_drvdata(pdev);
206	if (chip == NULL)
207		return -ENODEV;
208
209	clk_unprepare(chip->clk);
210
211	return pwmchip_remove(&chip->chip);
212}
213
214static struct platform_driver vt8500_pwm_driver = {
215	.probe		= vt8500_pwm_probe,
216	.remove		= vt8500_pwm_remove,
217	.driver		= {
218		.name	= "vt8500-pwm",
219		.owner	= THIS_MODULE,
220		.of_match_table = vt8500_pwm_dt_ids,
221	},
222};
223module_platform_driver(vt8500_pwm_driver);
224
225MODULE_DESCRIPTION("VT8500 PWM Driver");
226MODULE_AUTHOR("Tony Prisk <linux@prisktech.co.nz>");
227MODULE_LICENSE("GPL v2");
228