52297c3ab246c38a78e3580895c21e1c00d7b6f6
[linux-2.6.git] / drivers / leds / leds-atmel-pwm.c
1 #include <linux/kernel.h>
2 #include <linux/platform_device.h>
3 #include <linux/leds.h>
4 #include <linux/io.h>
5 #include <linux/atmel_pwm.h>
6
7
8 struct pwmled {
9         struct led_classdev     cdev;
10         struct pwm_channel      pwmc;
11         struct gpio_led         *desc;
12         u32                     mult;
13         u8                      active_low;
14 };
15
16
17 /*
18  * For simplicity, we use "brightness" as if it were a linear function
19  * of PWM duty cycle.  However, a logarithmic function of duty cycle is
20  * probably a better match for perceived brightness: two is half as bright
21  * as four, four is half as bright as eight, etc
22  */
23 static void pwmled_brightness(struct led_classdev *cdev, enum led_brightness b)
24 {
25         struct pwmled            *led;
26
27         /* update the duty cycle for the *next* period */
28         led = container_of(cdev, struct pwmled, cdev);
29         pwm_channel_writel(&led->pwmc, PWM_CUPD, led->mult * (unsigned) b);
30 }
31
32 /*
33  * NOTE:  we reuse the platform_data structure of GPIO leds,
34  * but repurpose its "gpio" number as a PWM channel number.
35  */
36 static int __init pwmled_probe(struct platform_device *pdev)
37 {
38         const struct gpio_led_platform_data     *pdata;
39         struct pwmled                           *leds;
40         int                                     i;
41         int                                     status;
42
43         pdata = pdev->dev.platform_data;
44         if (!pdata || pdata->num_leds < 1)
45                 return -ENODEV;
46
47         leds = kcalloc(pdata->num_leds, sizeof(*leds), GFP_KERNEL);
48         if (!leds)
49                 return -ENOMEM;
50
51         for (i = 0; i < pdata->num_leds; i++) {
52                 struct pwmled           *led = leds + i;
53                 const struct gpio_led   *dat = pdata->leds + i;
54                 u32                     tmp;
55
56                 led->cdev.name = dat->name;
57                 led->cdev.brightness = LED_OFF;
58                 led->cdev.brightness_set = pwmled_brightness;
59                 led->cdev.default_trigger = dat->default_trigger;
60
61                 led->active_low = dat->active_low;
62
63                 status = pwm_channel_alloc(dat->gpio, &led->pwmc);
64                 if (status < 0)
65                         goto err;
66
67                 /*
68                  * Prescale clock by 2^x, so PWM counts in low MHz.
69                  * Start each cycle with the LED active, so increasing
70                  * the duty cycle gives us more time on (== brighter).
71                  */
72                 tmp = 5;
73                 if (!led->active_low)
74                         tmp |= PWM_CPR_CPOL;
75                 pwm_channel_writel(&led->pwmc, PWM_CMR, tmp);
76
77                 /*
78                  * Pick a period so PWM cycles at 100+ Hz; and a multiplier
79                  * for scaling duty cycle:  brightness * mult.
80                  */
81                 tmp = (led->pwmc.mck / (1 << 5)) / 100;
82                 tmp /= 255;
83                 led->mult = tmp;
84                 pwm_channel_writel(&led->pwmc, PWM_CDTY,
85                                 led->cdev.brightness * 255);
86                 pwm_channel_writel(&led->pwmc, PWM_CPRD,
87                                 LED_FULL * tmp);
88
89                 pwm_channel_enable(&led->pwmc);
90
91                 /* Hand it over to the LED framework */
92                 status = led_classdev_register(&pdev->dev, &led->cdev);
93                 if (status < 0) {
94                         pwm_channel_free(&led->pwmc);
95                         goto err;
96                 }
97         }
98
99         platform_set_drvdata(pdev, leds);
100         return 0;
101
102 err:
103         if (i > 0) {
104                 for (i = i - 1; i >= 0; i--) {
105                         led_classdev_unregister(&leds[i].cdev);
106                         pwm_channel_free(&leds[i].pwmc);
107                 }
108         }
109         kfree(leds);
110
111         return status;
112 }
113
114 static int __exit pwmled_remove(struct platform_device *pdev)
115 {
116         const struct gpio_led_platform_data     *pdata;
117         struct pwmled                           *leds;
118         unsigned                                i;
119
120         pdata = pdev->dev.platform_data;
121         leds = platform_get_drvdata(pdev);
122
123         for (i = 0; i < pdata->num_leds; i++) {
124                 struct pwmled           *led = leds + i;
125
126                 led_classdev_unregister(&led->cdev);
127                 pwm_channel_free(&led->pwmc);
128         }
129
130         kfree(leds);
131         platform_set_drvdata(pdev, NULL);
132         return 0;
133 }
134
135 /* work with hotplug and coldplug */
136 MODULE_ALIAS("platform:leds-atmel-pwm");
137
138 static struct platform_driver pwmled_driver = {
139         .driver = {
140                 .name =         "leds-atmel-pwm",
141                 .owner =        THIS_MODULE,
142         },
143         /* REVISIT add suspend() and resume() methods */
144         .remove =       __exit_p(pwmled_remove),
145 };
146
147 static int __init modinit(void)
148 {
149         return platform_driver_probe(&pwmled_driver, pwmled_probe);
150 }
151 module_init(modinit);
152
153 static void __exit modexit(void)
154 {
155         platform_driver_unregister(&pwmled_driver);
156 }
157 module_exit(modexit);
158
159 MODULE_DESCRIPTION("Driver for LEDs with PWM-controlled brightness");
160 MODULE_LICENSE("GPL");