aboutsummaryrefslogtreecommitdiffstats
path: root/arch/arm/plat-mxc/pwm.c
blob: 7a61ef8f471a49fd3ac0b67540f949cf13eaaa43 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
/*
 * simple driver for PWM (Pulse Width Modulator) controller
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Derived from pxa PWM driver by eric miao <eric.miao@marvell.com>
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/pwm.h>
#include <mach/hardware.h>


/* i.MX1 and i.MX21 share the same PWM function block: */

#define MX1_PWMC    0x00   /* PWM Control Register */
#define MX1_PWMS    0x04   /* PWM Sample Register */
#define MX1_PWMP    0x08   /* PWM Period Register */


/* i.MX27, i.MX31, i.MX35 share the same PWM function block: */

#define MX3_PWMCR                 0x00    /* PWM Control Register */
#define MX3_PWMSAR                0x0C    /* PWM Sample Register */
#define MX3_PWMPR                 0x10    /* PWM Period Register */
#define MX3_PWMCR_PRESCALER(x)    (((x - 1) & 0xFFF) << 4)
#define MX3_PWMCR_CLKSRC_IPG_HIGH (2 << 16)
#define MX3_PWMCR_CLKSRC_IPG      (1 << 16)
#define MX3_PWMCR_EN              (1 << 0)



struct pwm_device {
	struct list_head	node;
	struct platform_device *pdev;

	const char	*label;
	struct clk	*clk;

	int		clk_enabled;
	void __iomem	*mmio_base;

	unsigned int	use_count;
	unsigned int	pwm_id;
};

int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
{
	if (pwm == NULL || period_ns == 0 || duty_ns > period_ns)
		return -EINVAL;

	if (cpu_is_mx27() || cpu_is_mx3() || cpu_is_mx25() || cpu_is_mx51()) {
		unsigned long long c;
		unsigned long period_cycles, duty_cycles, prescale;
		u32 cr;

		c = clk_get_rate(pwm->clk);
		c = c * period_ns;
		do_div(c, 1000000000);
		period_cycles = c;

		prescale = period_cycles / 0x10000 + 1;

		period_cycles /= prescale;
		c = (unsigned long long)period_cycles * duty_ns;
		do_div(c, period_ns);
		duty_cycles = c;

		writel(duty_cycles, pwm->mmio_base + MX3_PWMSAR);
		writel(period_cycles, pwm->mmio_base + MX3_PWMPR);

		cr = MX3_PWMCR_PRESCALER(prescale) | MX3_PWMCR_EN;

		if (cpu_is_mx25())
			cr |= MX3_PWMCR_CLKSRC_IPG;
		else
			cr |= MX3_PWMCR_CLKSRC_IPG_HIGH;

		writel(cr, pwm->mmio_base + MX3_PWMCR);
	} else if (cpu_is_mx1() || cpu_is_mx21()) {
		/* The PWM subsystem allows for exact frequencies. However,
		 * I cannot connect a scope on my device to the PWM line and
		 * thus cannot provide the program the PWM controller
		 * exactly. Instead, I'm relying on the fact that the
		 * Bootloader (u-boot or WinCE+haret) has programmed the PWM
		 * function group already. So I'll just modify the PWM sample
		 * register to follow the ratio of duty_ns vs. period_ns
		 * accordingly.
		 *
		 * This is good enough for programming the brightness of
		 * the LCD backlight.
		 *
		 * The real implementation would divide PERCLK[0] first by
		 * both the prescaler (/1 .. /128) and then by CLKSEL
		 * (/2 .. /16).
		 */
		u32 max = readl(pwm->mmio_base + MX1_PWMP);
		u32 p = max * duty_ns / period_ns;
		writel(max - p, pwm->mmio_base + MX1_PWMS);
	} else {
		BUG();
	}

	return 0;
}
EXPORT_SYMBOL(pwm_config);

int pwm_enable(struct pwm_device *pwm)
{
	int rc = 0;

	if (!pwm->clk_enabled) {
		rc = clk_enable(pwm->clk);
		if (!rc)
			pwm->clk_enabled = 1;
	}
	return rc;
}
EXPORT_SYMBOL(pwm_enable);

void pwm_disable(struct pwm_device *pwm)
{
	writel(0, pwm->mmio_base + MX3_PWMCR);

	if (pwm->clk_enabled) {
		clk_disable(pwm->clk);
		pwm->clk_enabled = 0;
	}
}
EXPORT_SYMBOL(pwm_disable);

static DEFINE_MUTEX(pwm_lock);
static LIST_HEAD(pwm_list);

struct pwm_device *pwm_request(int pwm_id, const char *label)
{
	struct pwm_device *pwm;
	int found = 0;

	mutex_lock(&pwm_lock);

	list_for_each_entry(pwm, &pwm_list, node) {
		if (pwm->pwm_id == pwm_id) {
			found = 1;
			break;
		}
	}

	if (found) {
		if (pwm->use_count == 0) {
			pwm->use_count++;
			pwm->label = label;
		} else
			pwm = ERR_PTR(-EBUSY);
	} else
		pwm = ERR_PTR(-ENOENT);

	mutex_unlock(&pwm_lock);
	return pwm;
}
EXPORT_SYMBOL(pwm_request);

void pwm_free(struct pwm_device *pwm)
{
	mutex_lock(&pwm_lock);

	if (pwm->use_count) {
		pwm->use_count--;
		pwm->label = NULL;
	} else
		pr_warning("PWM device already freed\n");

	mutex_unlock(&pwm_lock);
}
EXPORT_SYMBOL(pwm_free);

static int __devinit mxc_pwm_probe(struct platform_device *pdev)
{
	struct pwm_device *pwm;
	struct resource *r;
	int ret = 0;

	pwm = kzalloc(sizeof(struct pwm_device), GFP_KERNEL);
	if (pwm == NULL) {
		dev_err(&pdev->dev, "failed to allocate memory\n");
		return -ENOMEM;
	}

	pwm->clk = clk_get(&pdev->dev, "pwm");

	if (IS_ERR(pwm->clk)) {
		ret = PTR_ERR(pwm->clk);
		goto err_free;
	}

	pwm->clk_enabled = 0;

	pwm->use_count = 0;
	pwm->pwm_id = pdev->id;
	pwm->pdev = pdev;

	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (r == NULL) {
		dev_err(&pdev->dev, "no memory resource defined\n");
		ret = -ENODEV;
		goto err_free_clk;
	}

	r = request_mem_region(r->start, r->end - r->start + 1, pdev->name);
	if (r == NULL) {
		dev_err(&pdev->dev, "failed to request memory resource\n");
		ret = -EBUSY;
		goto err_free_clk;
	}

	pwm->mmio_base = ioremap(r->start, r->end - r->start + 1);
	if (pwm->mmio_base == NULL) {
		dev_err(&pdev->dev, "failed to ioremap() registers\n");
		ret = -ENODEV;
		goto err_free_mem;
	}

	mutex_lock(&pwm_lock);
	list_add_tail(&pwm->node, &pwm_list);
	mutex_unlock(&pwm_lock);

	platform_set_drvdata(pdev, pwm);
	return 0;

err_free_mem:
	release_mem_region(r->start, r->end - r->start + 1);
err_free_clk:
	clk_put(pwm->clk);
err_free:
	kfree(pwm);
	return ret;
}

static int __devexit mxc_pwm_remove(struct platform_device *pdev)
{
	struct pwm_device *pwm;
	struct resource *r;

	pwm = platform_get_drvdata(pdev);
	if (pwm == NULL)
		return -ENODEV;

	mutex_lock(&pwm_lock);
	list_del(&pwm->node);
	mutex_unlock(&pwm_lock);

	iounmap(pwm->mmio_base);

	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	release_mem_region(r->start, r->end - r->start + 1);

	clk_put(pwm->clk);

	kfree(pwm);
	return 0;
}

static struct platform_driver mxc_pwm_driver = {
	.driver		= {
		.name	= "mxc_pwm",
	},
	.probe		= mxc_pwm_probe,
	.remove		= __devexit_p(mxc_pwm_remove),
};

static int __init mxc_pwm_init(void)
{
	return platform_driver_register(&mxc_pwm_driver);
}
arch_initcall(mxc_pwm_init);

static void __exit mxc_pwm_exit(void)
{
	platform_driver_unregister(&mxc_pwm_driver);
}
module_exit(mxc_pwm_exit);

MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");