xref: /openbmc/linux/drivers/pwm/pwm-vt8500.c (revision 9be08a27) 
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 
58 struct 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)
67 static 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 
80 static 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 
134 static 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 
154 static 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 
167 static 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 
187 static const 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 
195 static const struct of_device_id vt8500_pwm_dt_ids[] = {
196 	{ .compatible = "via,vt8500-pwm", },
197 	{ /* Sentinel */ }
198 };
199 MODULE_DEVICE_TABLE(of, vt8500_pwm_dt_ids);
200 
201 static 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 		clk_unprepare(chip->clk);
245 		return ret;
246 	}
247 
248 	platform_set_drvdata(pdev, chip);
249 	return ret;
250 }
251 
252 static int vt8500_pwm_remove(struct platform_device *pdev)
253 {
254 	struct vt8500_chip *chip;
255 
256 	chip = platform_get_drvdata(pdev);
257 	if (chip == NULL)
258 		return -ENODEV;
259 
260 	clk_unprepare(chip->clk);
261 
262 	return pwmchip_remove(&chip->chip);
263 }
264 
265 static struct platform_driver vt8500_pwm_driver = {
266 	.probe		= vt8500_pwm_probe,
267 	.remove		= vt8500_pwm_remove,
268 	.driver		= {
269 		.name	= "vt8500-pwm",
270 		.of_match_table = vt8500_pwm_dt_ids,
271 	},
272 };
273 module_platform_driver(vt8500_pwm_driver);
274 
275 MODULE_DESCRIPTION("VT8500 PWM Driver");
276 MODULE_AUTHOR("Tony Prisk <linux@prisktech.co.nz>");
277 MODULE_LICENSE("GPL v2");
278