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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> | |
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; | |
e49575f4 | 40 | int i; |
de5c9ede DB |
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 | ||
3c4ded97 KS |
135 | /* work with hotplug and coldplug */ |
136 | MODULE_ALIAS("platform:leds-atmel-pwm"); | |
137 | ||
de5c9ede DB |
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"); |