pwm-vt8500.c revision b9f87404dde26769429b470e1d4854a3c380cf26 
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
39#define REG_CTRL(pwm)		(((pwm) << 4) + 0x00)
40#define REG_SCALAR(pwm)		(((pwm) << 4) + 0x04)
41#define REG_PERIOD(pwm)		(((pwm) << 4) + 0x08)
42#define REG_DUTY(pwm)		(((pwm) << 4) + 0x0C)
43#define REG_STATUS		0x40
44
45#define CTRL_ENABLE		BIT(0)
46#define CTRL_INVERT		BIT(1)
47#define CTRL_AUTOLOAD		BIT(2)
48#define CTRL_STOP_IMM		BIT(3)
49#define CTRL_LOAD_PRESCALE	BIT(4)
50#define CTRL_LOAD_PERIOD	BIT(5)
51
52#define STATUS_CTRL_UPDATE	BIT(0)
53#define STATUS_SCALAR_UPDATE	BIT(1)
54#define STATUS_PERIOD_UPDATE	BIT(2)
55#define STATUS_DUTY_UPDATE	BIT(3)
56#define STATUS_ALL_UPDATE	0x0F
57
58struct vt8500_chip {
59	struct pwm_chip chip;
60	void __iomem *base;
61	struct clk *clk;
62};
63
64#define to_vt8500_chip(chip)	container_of(chip, struct vt8500_chip, chip)
65
66#define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t)
67static inline void pwm_busy_wait(struct vt8500_chip *vt8500, int nr, u8 bitmask)
68{
69	int loops = msecs_to_loops(10);
70	u32 mask = bitmask << (nr << 8);
71
72	while ((readl(vt8500->base + REG_STATUS) & mask) && --loops)
73		cpu_relax();
74
75	if (unlikely(!loops))
76		dev_warn(vt8500->chip.dev, "Waiting for status bits 0x%x to clear timed out\n",
77			 mask);
78}
79
80static int vt8500_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
81		int duty_ns, int period_ns)
82{
83	struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
84	unsigned long long c;
85	unsigned long period_cycles, prescale, pv, dc;
86	int err;
87	u32 val;
88
89	err = clk_enable(vt8500->clk);
90	if (err < 0) {
91		dev_err(chip->dev, "failed to enable clock\n");
92		return err;
93	}
94
95	c = clk_get_rate(vt8500->clk);
96	c = c * period_ns;
97	do_div(c, 1000000000);
98	period_cycles = c;
99
100	if (period_cycles < 1)
101		period_cycles = 1;
102	prescale = (period_cycles - 1) / 4096;
103	pv = period_cycles / (prescale + 1) - 1;
104	if (pv > 4095)
105		pv = 4095;
106
107	if (prescale > 1023) {
108		clk_disable(vt8500->clk);
109		return -EINVAL;
110	}
111
112	c = (unsigned long long)pv * duty_ns;
113	do_div(c, period_ns);
114	dc = c;
115
116	writel(prescale, vt8500->base + REG_SCALAR(pwm->hwpwm));
117	pwm_busy_wait(vt8500, pwm->hwpwm, STATUS_SCALAR_UPDATE);
118
119	writel(pv, vt8500->base + REG_PERIOD(pwm->hwpwm));
120	pwm_busy_wait(vt8500, pwm->hwpwm, STATUS_PERIOD_UPDATE);
121
122	writel(dc, vt8500->base + REG_DUTY(pwm->hwpwm));
123	pwm_busy_wait(vt8500, pwm->hwpwm, STATUS_DUTY_UPDATE);
124
125	val = readl(vt8500->base + REG_CTRL(pwm->hwpwm));
126	val |= CTRL_AUTOLOAD;
127	writel(val, vt8500->base + REG_CTRL(pwm->hwpwm));
128	pwm_busy_wait(vt8500, pwm->hwpwm, STATUS_CTRL_UPDATE);
129
130	clk_disable(vt8500->clk);
131	return 0;
132}
133
134static int vt8500_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
135{
136	struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
137	int err;
138	u32 val;
139
140	err = clk_enable(vt8500->clk);
141	if (err < 0) {
142		dev_err(chip->dev, "failed to enable clock\n");
143		return err;
144	}
145
146	val = readl(vt8500->base + REG_CTRL(pwm->hwpwm));
147	val |= CTRL_ENABLE;
148	writel(val, vt8500->base + REG_CTRL(pwm->hwpwm));
149	pwm_busy_wait(vt8500, pwm->hwpwm, STATUS_CTRL_UPDATE);
150
151	return 0;
152}
153
154static void vt8500_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
155{
156	struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
157	u32 val;
158
159	val = readl(vt8500->base + REG_CTRL(pwm->hwpwm));
160	val &= ~CTRL_ENABLE;
161	writel(val, vt8500->base + REG_CTRL(pwm->hwpwm));
162	pwm_busy_wait(vt8500, pwm->hwpwm, STATUS_CTRL_UPDATE);
163
164	clk_disable(vt8500->clk);
165}
166
167static int vt8500_pwm_set_polarity(struct pwm_chip *chip,
168				   struct pwm_device *pwm,
169				   enum pwm_polarity polarity)
170{
171	struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
172	u32 val;
173
174	val = readl(vt8500->base + REG_CTRL(pwm->hwpwm));
175
176	if (polarity == PWM_POLARITY_INVERSED)
177		val |= CTRL_INVERT;
178	else
179		val &= ~CTRL_INVERT;
180
181	writel(val, vt8500->base + REG_CTRL(pwm->hwpwm));
182	pwm_busy_wait(vt8500, pwm->hwpwm, STATUS_CTRL_UPDATE);
183
184	return 0;
185}
186
187static struct pwm_ops vt8500_pwm_ops = {
188	.enable = vt8500_pwm_enable,
189	.disable = vt8500_pwm_disable,
190	.config = vt8500_pwm_config,
191	.set_polarity = vt8500_pwm_set_polarity,
192	.owner = THIS_MODULE,
193};
194
195static const struct of_device_id vt8500_pwm_dt_ids[] = {
196	{ .compatible = "via,vt8500-pwm", },
197	{ /* Sentinel */ }
198};
199MODULE_DEVICE_TABLE(of, vt8500_pwm_dt_ids);
200
201static int vt8500_pwm_probe(struct platform_device *pdev)
202{
203	struct vt8500_chip *chip;
204	struct resource *r;
205	struct device_node *np = pdev->dev.of_node;
206	int ret;
207
208	if (!np) {
209		dev_err(&pdev->dev, "invalid devicetree node\n");
210		return -EINVAL;
211	}
212
213	chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
214	if (chip == NULL)
215		return -ENOMEM;
216
217	chip->chip.dev = &pdev->dev;
218	chip->chip.ops = &vt8500_pwm_ops;
219	chip->chip.of_xlate = of_pwm_xlate_with_flags;
220	chip->chip.of_pwm_n_cells = 3;
221	chip->chip.base = -1;
222	chip->chip.npwm = VT8500_NR_PWMS;
223
224	chip->clk = devm_clk_get(&pdev->dev, NULL);
225	if (IS_ERR(chip->clk)) {
226		dev_err(&pdev->dev, "clock source not specified\n");
227		return PTR_ERR(chip->clk);
228	}
229
230	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
231	chip->base = devm_ioremap_resource(&pdev->dev, r);
232	if (IS_ERR(chip->base))
233		return PTR_ERR(chip->base);
234
235	ret = clk_prepare(chip->clk);
236	if (ret < 0) {
237		dev_err(&pdev->dev, "failed to prepare clock\n");
238		return ret;
239	}
240
241	ret = pwmchip_add(&chip->chip);
242	if (ret < 0) {
243		dev_err(&pdev->dev, "failed to add PWM chip\n");
244		return ret;
245	}
246
247	platform_set_drvdata(pdev, chip);
248	return ret;
249}
250
251static int vt8500_pwm_remove(struct platform_device *pdev)
252{
253	struct vt8500_chip *chip;
254
255	chip = platform_get_drvdata(pdev);
256	if (chip == NULL)
257		return -ENODEV;
258
259	clk_unprepare(chip->clk);
260
261	return pwmchip_remove(&chip->chip);
262}
263
264static struct platform_driver vt8500_pwm_driver = {
265	.probe		= vt8500_pwm_probe,
266	.remove		= vt8500_pwm_remove,
267	.driver		= {
268		.name	= "vt8500-pwm",
269		.owner	= THIS_MODULE,
270		.of_match_table = vt8500_pwm_dt_ids,
271	},
272};
273module_platform_driver(vt8500_pwm_driver);
274
275MODULE_DESCRIPTION("VT8500 PWM Driver");
276MODULE_AUTHOR("Tony Prisk <linux@prisktech.co.nz>");
277MODULE_LICENSE("GPL v2");
278