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
|
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/leds.h>
#include <linux/io.h>
#include <linux/atmel_pwm.h>
#include <linux/slab.h>
#include <linux/module.h>
struct pwmled {
struct led_classdev cdev;
struct pwm_channel pwmc;
struct gpio_led *desc;
u32 mult;
u8 active_low;
};
/*
* For simplicity, we use "brightness" as if it were a linear function
* of PWM duty cycle. However, a logarithmic function of duty cycle is
* probably a better match for perceived brightness: two is half as bright
* as four, four is half as bright as eight, etc
*/
static void pwmled_brightness(struct led_classdev *cdev, enum led_brightness b)
{
struct pwmled *led;
/* update the duty cycle for the *next* period */
led = container_of(cdev, struct pwmled, cdev);
pwm_channel_writel(&led->pwmc, PWM_CUPD, led->mult * (unsigned) b);
}
/*
* NOTE: we reuse the platform_data structure of GPIO leds,
* but repurpose its "gpio" number as a PWM channel number.
*/
static int __devinit pwmled_probe(struct platform_device *pdev)
{
const struct gpio_led_platform_data *pdata;
struct pwmled *leds;
int i;
int status;
pdata = pdev->dev.platform_data;
if (!pdata || pdata->num_leds < 1)
return -ENODEV;
leds = kcalloc(pdata->num_leds, sizeof(*leds), GFP_KERNEL);
if (!leds)
return -ENOMEM;
for (i = 0; i < pdata->num_leds; i++) {
struct pwmled *led = leds + i;
const struct gpio_led *dat = pdata->leds + i;
u32 tmp;
led->cdev.name = dat->name;
led->cdev.brightness = LED_OFF;
led->cdev.brightness_set = pwmled_brightness;
led->cdev.default_trigger = dat->default_trigger;
led->active_low = dat->active_low;
status = pwm_channel_alloc(dat->gpio, &led->pwmc);
if (status < 0)
goto err;
/*
* Prescale clock by 2^x, so PWM counts in low MHz.
* Start each cycle with the LED active, so increasing
* the duty cycle gives us more time on (== brighter).
*/
tmp = 5;
if (!led->active_low)
tmp |= PWM_CPR_CPOL;
pwm_channel_writel(&led->pwmc, PWM_CMR, tmp);
/*
* Pick a period so PWM cycles at 100+ Hz; and a multiplier
* for scaling duty cycle: brightness * mult.
*/
tmp = (led->pwmc.mck / (1 << 5)) / 100;
tmp /= 255;
led->mult = tmp;
pwm_channel_writel(&led->pwmc, PWM_CDTY,
led->cdev.brightness * 255);
pwm_channel_writel(&led->pwmc, PWM_CPRD,
LED_FULL * tmp);
pwm_channel_enable(&led->pwmc);
/* Hand it over to the LED framework */
status = led_classdev_register(&pdev->dev, &led->cdev);
if (status < 0) {
pwm_channel_free(&led->pwmc);
goto err;
}
}
platform_set_drvdata(pdev, leds);
return 0;
err:
if (i > 0) {
for (i = i - 1; i >= 0; i--) {
led_classdev_unregister(&leds[i].cdev);
pwm_channel_free(&leds[i].pwmc);
}
}
kfree(leds);
return status;
}
static int __exit pwmled_remove(struct platform_device *pdev)
{
const struct gpio_led_platform_data *pdata;
struct pwmled *leds;
unsigned i;
pdata = pdev->dev.platform_data;
leds = platform_get_drvdata(pdev);
for (i = 0; i < pdata->num_leds; i++) {
struct pwmled *led = leds + i;
led_classdev_unregister(&led->cdev);
pwm_channel_free(&led->pwmc);
}
kfree(leds);
platform_set_drvdata(pdev, NULL);
return 0;
}
static struct platform_driver pwmled_driver = {
.driver = {
.name = "leds-atmel-pwm",
.owner = THIS_MODULE,
},
/* REVISIT add suspend() and resume() methods */
.probe = pwmled_probe,
.remove = __exit_p(pwmled_remove),
};
module_platform_driver(pwmled_driver);
MODULE_DESCRIPTION("Driver for LEDs with PWM-controlled brightness");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:leds-atmel-pwm");
|
