1 /*
2 * simple driver for PWM (Pulse Width Modulator) controller
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
7 *
8 * Derived from pxa PWM driver by eric miao <eric.miao@marvell.com>
9 */
10
11 #include <linux/module.h>
12 #include <linux/kernel.h>
13 #include <linux/platform_device.h>
14 #include <linux/slab.h>
15 #include <linux/err.h>
16 #include <linux/clk.h>
17 #include <linux/io.h>
18 #include <linux/pwm.h>
19 #include <mach/hardware.h>
20
21
22 /* i.MX1 and i.MX21 share the same PWM function block: */
23
24 #define MX1_PWMC 0x00 /* PWM Control Register */
25 #define MX1_PWMS 0x04 /* PWM Sample Register */
26 #define MX1_PWMP 0x08 /* PWM Period Register */
27
28
29 /* i.MX27, i.MX31, i.MX35 share the same PWM function block: */
30
31 #define MX3_PWMCR 0x00 /* PWM Control Register */
32 #define MX3_PWMSAR 0x0C /* PWM Sample Register */
33 #define MX3_PWMPR 0x10 /* PWM Period Register */
34 #define MX3_PWMCR_PRESCALER(x) (((x - 1) & 0xFFF) << 4)
35 #define MX3_PWMCR_DOZEEN (1 << 24)
36 #define MX3_PWMCR_WAITEN (1 << 23)
37 #define MX3_PWMCR_DBGEN (1 << 22)
38 #define MX3_PWMCR_CLKSRC_IPG_HIGH (2 << 16)
39 #define MX3_PWMCR_CLKSRC_IPG (1 << 16)
40 #define MX3_PWMCR_EN (1 << 0)
41
42
43
44 struct pwm_device {
45 struct list_head node;
46 struct platform_device *pdev;
47
48 const char *label;
49 struct clk *clk;
50
51 int clk_enabled;
52 void __iomem *mmio_base;
53
54 unsigned int use_count;
55 unsigned int pwm_id;
56 };
57
pwm_config(struct pwm_device * pwm,int duty_ns,int period_ns)58 int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
59 {
60 if (pwm == NULL || period_ns == 0 || duty_ns > period_ns)
61 return -EINVAL;
62
63 if (!(cpu_is_mx1() || cpu_is_mx21())) {
64 unsigned long long c;
65 unsigned long period_cycles, duty_cycles, prescale;
66 u32 cr;
67
68 c = clk_get_rate(pwm->clk);
69 c = c * period_ns;
70 do_div(c, 1000000000);
71 period_cycles = c;
72
73 prescale = period_cycles / 0x10000 + 1;
74
75 period_cycles /= prescale;
76 c = (unsigned long long)period_cycles * duty_ns;
77 do_div(c, period_ns);
78 duty_cycles = c;
79
80 /*
81 * according to imx pwm RM, the real period value should be
82 * PERIOD value in PWMPR plus 2.
83 */
84 if (period_cycles > 2)
85 period_cycles -= 2;
86 else
87 period_cycles = 0;
88
89 writel(duty_cycles, pwm->mmio_base + MX3_PWMSAR);
90 writel(period_cycles, pwm->mmio_base + MX3_PWMPR);
91
92 cr = MX3_PWMCR_PRESCALER(prescale) |
93 MX3_PWMCR_DOZEEN | MX3_PWMCR_WAITEN |
94 MX3_PWMCR_DBGEN | MX3_PWMCR_EN;
95
96 if (cpu_is_mx25())
97 cr |= MX3_PWMCR_CLKSRC_IPG;
98 else
99 cr |= MX3_PWMCR_CLKSRC_IPG_HIGH;
100
101 writel(cr, pwm->mmio_base + MX3_PWMCR);
102 } else if (cpu_is_mx1() || cpu_is_mx21()) {
103 /* The PWM subsystem allows for exact frequencies. However,
104 * I cannot connect a scope on my device to the PWM line and
105 * thus cannot provide the program the PWM controller
106 * exactly. Instead, I'm relying on the fact that the
107 * Bootloader (u-boot or WinCE+haret) has programmed the PWM
108 * function group already. So I'll just modify the PWM sample
109 * register to follow the ratio of duty_ns vs. period_ns
110 * accordingly.
111 *
112 * This is good enough for programming the brightness of
113 * the LCD backlight.
114 *
115 * The real implementation would divide PERCLK[0] first by
116 * both the prescaler (/1 .. /128) and then by CLKSEL
117 * (/2 .. /16).
118 */
119 u32 max = readl(pwm->mmio_base + MX1_PWMP);
120 u32 p = max * duty_ns / period_ns;
121 writel(max - p, pwm->mmio_base + MX1_PWMS);
122 } else {
123 BUG();
124 }
125
126 return 0;
127 }
128 EXPORT_SYMBOL(pwm_config);
129
pwm_enable(struct pwm_device * pwm)130 int pwm_enable(struct pwm_device *pwm)
131 {
132 int rc = 0;
133
134 if (!pwm->clk_enabled) {
135 rc = clk_enable(pwm->clk);
136 if (!rc)
137 pwm->clk_enabled = 1;
138 }
139 return rc;
140 }
141 EXPORT_SYMBOL(pwm_enable);
142
pwm_disable(struct pwm_device * pwm)143 void pwm_disable(struct pwm_device *pwm)
144 {
145 writel(0, pwm->mmio_base + MX3_PWMCR);
146
147 if (pwm->clk_enabled) {
148 clk_disable(pwm->clk);
149 pwm->clk_enabled = 0;
150 }
151 }
152 EXPORT_SYMBOL(pwm_disable);
153
154 static DEFINE_MUTEX(pwm_lock);
155 static LIST_HEAD(pwm_list);
156
pwm_request(int pwm_id,const char * label)157 struct pwm_device *pwm_request(int pwm_id, const char *label)
158 {
159 struct pwm_device *pwm;
160 int found = 0;
161
162 mutex_lock(&pwm_lock);
163
164 list_for_each_entry(pwm, &pwm_list, node) {
165 if (pwm->pwm_id == pwm_id) {
166 found = 1;
167 break;
168 }
169 }
170
171 if (found) {
172 if (pwm->use_count == 0) {
173 pwm->use_count++;
174 pwm->label = label;
175 } else
176 pwm = ERR_PTR(-EBUSY);
177 } else
178 pwm = ERR_PTR(-ENOENT);
179
180 mutex_unlock(&pwm_lock);
181 return pwm;
182 }
183 EXPORT_SYMBOL(pwm_request);
184
pwm_free(struct pwm_device * pwm)185 void pwm_free(struct pwm_device *pwm)
186 {
187 mutex_lock(&pwm_lock);
188
189 if (pwm->use_count) {
190 pwm->use_count--;
191 pwm->label = NULL;
192 } else
193 pr_warning("PWM device already freed\n");
194
195 mutex_unlock(&pwm_lock);
196 }
197 EXPORT_SYMBOL(pwm_free);
198
mxc_pwm_probe(struct platform_device * pdev)199 static int __devinit mxc_pwm_probe(struct platform_device *pdev)
200 {
201 struct pwm_device *pwm;
202 struct resource *r;
203 int ret = 0;
204
205 pwm = kzalloc(sizeof(struct pwm_device), GFP_KERNEL);
206 if (pwm == NULL) {
207 dev_err(&pdev->dev, "failed to allocate memory\n");
208 return -ENOMEM;
209 }
210
211 pwm->clk = clk_get(&pdev->dev, "pwm");
212
213 if (IS_ERR(pwm->clk)) {
214 ret = PTR_ERR(pwm->clk);
215 goto err_free;
216 }
217
218 pwm->clk_enabled = 0;
219
220 pwm->use_count = 0;
221 pwm->pwm_id = pdev->id;
222 pwm->pdev = pdev;
223
224 r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
225 if (r == NULL) {
226 dev_err(&pdev->dev, "no memory resource defined\n");
227 ret = -ENODEV;
228 goto err_free_clk;
229 }
230
231 r = request_mem_region(r->start, resource_size(r), pdev->name);
232 if (r == NULL) {
233 dev_err(&pdev->dev, "failed to request memory resource\n");
234 ret = -EBUSY;
235 goto err_free_clk;
236 }
237
238 pwm->mmio_base = ioremap(r->start, resource_size(r));
239 if (pwm->mmio_base == NULL) {
240 dev_err(&pdev->dev, "failed to ioremap() registers\n");
241 ret = -ENODEV;
242 goto err_free_mem;
243 }
244
245 mutex_lock(&pwm_lock);
246 list_add_tail(&pwm->node, &pwm_list);
247 mutex_unlock(&pwm_lock);
248
249 platform_set_drvdata(pdev, pwm);
250 return 0;
251
252 err_free_mem:
253 release_mem_region(r->start, resource_size(r));
254 err_free_clk:
255 clk_put(pwm->clk);
256 err_free:
257 kfree(pwm);
258 return ret;
259 }
260
mxc_pwm_remove(struct platform_device * pdev)261 static int __devexit mxc_pwm_remove(struct platform_device *pdev)
262 {
263 struct pwm_device *pwm;
264 struct resource *r;
265
266 pwm = platform_get_drvdata(pdev);
267 if (pwm == NULL)
268 return -ENODEV;
269
270 mutex_lock(&pwm_lock);
271 list_del(&pwm->node);
272 mutex_unlock(&pwm_lock);
273
274 iounmap(pwm->mmio_base);
275
276 r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
277 release_mem_region(r->start, resource_size(r));
278
279 clk_put(pwm->clk);
280
281 kfree(pwm);
282 return 0;
283 }
284
285 static struct platform_driver mxc_pwm_driver = {
286 .driver = {
287 .name = "mxc_pwm",
288 },
289 .probe = mxc_pwm_probe,
290 .remove = __devexit_p(mxc_pwm_remove),
291 };
292
mxc_pwm_init(void)293 static int __init mxc_pwm_init(void)
294 {
295 return platform_driver_register(&mxc_pwm_driver);
296 }
297 arch_initcall(mxc_pwm_init);
298
mxc_pwm_exit(void)299 static void __exit mxc_pwm_exit(void)
300 {
301 platform_driver_unregister(&mxc_pwm_driver);
302 }
303 module_exit(mxc_pwm_exit);
304
305 MODULE_LICENSE("GPL v2");
306 MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");
307