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de5c9ede DB |
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> | |
5a0e3ad6 | 6 | #include <linux/slab.h> |
54f4dedb | 7 | #include <linux/module.h> |
de5c9ede DB |
8 | |
9 | ||
10 | struct pwmled { | |
11 | struct led_classdev cdev; | |
12 | struct pwm_channel pwmc; | |
13 | struct gpio_led *desc; | |
14 | u32 mult; | |
15 | u8 active_low; | |
16 | }; | |
17 | ||
18 | ||
19 | /* | |
20 | * For simplicity, we use "brightness" as if it were a linear function | |
21 | * of PWM duty cycle. However, a logarithmic function of duty cycle is | |
22 | * probably a better match for perceived brightness: two is half as bright | |
23 | * as four, four is half as bright as eight, etc | |
24 | */ | |
25 | static void pwmled_brightness(struct led_classdev *cdev, enum led_brightness b) | |
26 | { | |
27 | struct pwmled *led; | |
28 | ||
29 | /* update the duty cycle for the *next* period */ | |
30 | led = container_of(cdev, struct pwmled, cdev); | |
31 | pwm_channel_writel(&led->pwmc, PWM_CUPD, led->mult * (unsigned) b); | |
32 | } | |
33 | ||
34 | /* | |
35 | * NOTE: we reuse the platform_data structure of GPIO leds, | |
36 | * but repurpose its "gpio" number as a PWM channel number. | |
37 | */ | |
38 | static int __init pwmled_probe(struct platform_device *pdev) | |
39 | { | |
40 | const struct gpio_led_platform_data *pdata; | |
41 | struct pwmled *leds; | |
e49575f4 | 42 | int i; |
de5c9ede DB |
43 | int status; |
44 | ||
45 | pdata = pdev->dev.platform_data; | |
46 | if (!pdata || pdata->num_leds < 1) | |
47 | return -ENODEV; | |
48 | ||
49 | leds = kcalloc(pdata->num_leds, sizeof(*leds), GFP_KERNEL); | |
50 | if (!leds) | |
51 | return -ENOMEM; | |
52 | ||
53 | for (i = 0; i < pdata->num_leds; i++) { | |
54 | struct pwmled *led = leds + i; | |
55 | const struct gpio_led *dat = pdata->leds + i; | |
56 | u32 tmp; | |
57 | ||
58 | led->cdev.name = dat->name; | |
59 | led->cdev.brightness = LED_OFF; | |
60 | led->cdev.brightness_set = pwmled_brightness; | |
61 | led->cdev.default_trigger = dat->default_trigger; | |
62 | ||
63 | led->active_low = dat->active_low; | |
64 | ||
65 | status = pwm_channel_alloc(dat->gpio, &led->pwmc); | |
66 | if (status < 0) | |
67 | goto err; | |
68 | ||
69 | /* | |
70 | * Prescale clock by 2^x, so PWM counts in low MHz. | |
71 | * Start each cycle with the LED active, so increasing | |
72 | * the duty cycle gives us more time on (== brighter). | |
73 | */ | |
74 | tmp = 5; | |
75 | if (!led->active_low) | |
76 | tmp |= PWM_CPR_CPOL; | |
77 | pwm_channel_writel(&led->pwmc, PWM_CMR, tmp); | |
78 | ||
79 | /* | |
80 | * Pick a period so PWM cycles at 100+ Hz; and a multiplier | |
81 | * for scaling duty cycle: brightness * mult. | |
82 | */ | |
83 | tmp = (led->pwmc.mck / (1 << 5)) / 100; | |
84 | tmp /= 255; | |
85 | led->mult = tmp; | |
86 | pwm_channel_writel(&led->pwmc, PWM_CDTY, | |
87 | led->cdev.brightness * 255); | |
88 | pwm_channel_writel(&led->pwmc, PWM_CPRD, | |
89 | LED_FULL * tmp); | |
90 | ||
91 | pwm_channel_enable(&led->pwmc); | |
92 | ||
93 | /* Hand it over to the LED framework */ | |
94 | status = led_classdev_register(&pdev->dev, &led->cdev); | |
95 | if (status < 0) { | |
96 | pwm_channel_free(&led->pwmc); | |
97 | goto err; | |
98 | } | |
99 | } | |
100 | ||
101 | platform_set_drvdata(pdev, leds); | |
102 | return 0; | |
103 | ||
104 | err: | |
105 | if (i > 0) { | |
106 | for (i = i - 1; i >= 0; i--) { | |
107 | led_classdev_unregister(&leds[i].cdev); | |
108 | pwm_channel_free(&leds[i].pwmc); | |
109 | } | |
110 | } | |
111 | kfree(leds); | |
112 | ||
113 | return status; | |
114 | } | |
115 | ||
116 | static int __exit pwmled_remove(struct platform_device *pdev) | |
117 | { | |
118 | const struct gpio_led_platform_data *pdata; | |
119 | struct pwmled *leds; | |
120 | unsigned i; | |
121 | ||
122 | pdata = pdev->dev.platform_data; | |
123 | leds = platform_get_drvdata(pdev); | |
124 | ||
125 | for (i = 0; i < pdata->num_leds; i++) { | |
126 | struct pwmled *led = leds + i; | |
127 | ||
128 | led_classdev_unregister(&led->cdev); | |
129 | pwm_channel_free(&led->pwmc); | |
130 | } | |
131 | ||
132 | kfree(leds); | |
133 | platform_set_drvdata(pdev, NULL); | |
134 | return 0; | |
135 | } | |
136 | ||
137 | static struct platform_driver pwmled_driver = { | |
138 | .driver = { | |
139 | .name = "leds-atmel-pwm", | |
140 | .owner = THIS_MODULE, | |
141 | }, | |
142 | /* REVISIT add suspend() and resume() methods */ | |
892a8843 | 143 | .probe = pwmled_probe, |
de5c9ede DB |
144 | .remove = __exit_p(pwmled_remove), |
145 | }; | |
146 | ||
892a8843 | 147 | module_platform_driver(pwmled_driver); |
de5c9ede DB |
148 | |
149 | MODULE_DESCRIPTION("Driver for LEDs with PWM-controlled brightness"); | |
150 | MODULE_LICENSE("GPL"); | |
892a8843 | 151 | MODULE_ALIAS("platform:leds-atmel-pwm"); |