xref: /openbmc/linux/drivers/video/backlight/pwm_bl.c (revision b6dcefde)
1 /*
2  * linux/drivers/video/backlight/pwm_bl.c
3  *
4  * simple PWM based backlight control, board code has to setup
5  * 1) pin configuration so PWM waveforms can output
6  * 2) platform_data being correctly configured
7  *
8  * This program is free software; you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License version 2 as
10  * published by the Free Software Foundation.
11  */
12 
13 #include <linux/module.h>
14 #include <linux/kernel.h>
15 #include <linux/init.h>
16 #include <linux/platform_device.h>
17 #include <linux/fb.h>
18 #include <linux/backlight.h>
19 #include <linux/err.h>
20 #include <linux/pwm.h>
21 #include <linux/pwm_backlight.h>
22 
23 struct pwm_bl_data {
24 	struct pwm_device	*pwm;
25 	struct device		*dev;
26 	unsigned int		period;
27 	int			(*notify)(struct device *,
28 					  int brightness);
29 };
30 
31 static int pwm_backlight_update_status(struct backlight_device *bl)
32 {
33 	struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
34 	int brightness = bl->props.brightness;
35 	int max = bl->props.max_brightness;
36 
37 	if (bl->props.power != FB_BLANK_UNBLANK)
38 		brightness = 0;
39 
40 	if (bl->props.fb_blank != FB_BLANK_UNBLANK)
41 		brightness = 0;
42 
43 	if (pb->notify)
44 		brightness = pb->notify(pb->dev, brightness);
45 
46 	if (brightness == 0) {
47 		pwm_config(pb->pwm, 0, pb->period);
48 		pwm_disable(pb->pwm);
49 	} else {
50 		pwm_config(pb->pwm, brightness * pb->period / max, pb->period);
51 		pwm_enable(pb->pwm);
52 	}
53 	return 0;
54 }
55 
56 static int pwm_backlight_get_brightness(struct backlight_device *bl)
57 {
58 	return bl->props.brightness;
59 }
60 
61 static const struct backlight_ops pwm_backlight_ops = {
62 	.update_status	= pwm_backlight_update_status,
63 	.get_brightness	= pwm_backlight_get_brightness,
64 };
65 
66 static int pwm_backlight_probe(struct platform_device *pdev)
67 {
68 	struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
69 	struct backlight_device *bl;
70 	struct pwm_bl_data *pb;
71 	int ret;
72 
73 	if (!data) {
74 		dev_err(&pdev->dev, "failed to find platform data\n");
75 		return -EINVAL;
76 	}
77 
78 	if (data->init) {
79 		ret = data->init(&pdev->dev);
80 		if (ret < 0)
81 			return ret;
82 	}
83 
84 	pb = kzalloc(sizeof(*pb), GFP_KERNEL);
85 	if (!pb) {
86 		dev_err(&pdev->dev, "no memory for state\n");
87 		ret = -ENOMEM;
88 		goto err_alloc;
89 	}
90 
91 	pb->period = data->pwm_period_ns;
92 	pb->notify = data->notify;
93 	pb->dev = &pdev->dev;
94 
95 	pb->pwm = pwm_request(data->pwm_id, "backlight");
96 	if (IS_ERR(pb->pwm)) {
97 		dev_err(&pdev->dev, "unable to request PWM for backlight\n");
98 		ret = PTR_ERR(pb->pwm);
99 		goto err_pwm;
100 	} else
101 		dev_dbg(&pdev->dev, "got pwm for backlight\n");
102 
103 	bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev,
104 			pb, &pwm_backlight_ops);
105 	if (IS_ERR(bl)) {
106 		dev_err(&pdev->dev, "failed to register backlight\n");
107 		ret = PTR_ERR(bl);
108 		goto err_bl;
109 	}
110 
111 	bl->props.max_brightness = data->max_brightness;
112 	bl->props.brightness = data->dft_brightness;
113 	backlight_update_status(bl);
114 
115 	platform_set_drvdata(pdev, bl);
116 	return 0;
117 
118 err_bl:
119 	pwm_free(pb->pwm);
120 err_pwm:
121 	kfree(pb);
122 err_alloc:
123 	if (data->exit)
124 		data->exit(&pdev->dev);
125 	return ret;
126 }
127 
128 static int pwm_backlight_remove(struct platform_device *pdev)
129 {
130 	struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
131 	struct backlight_device *bl = platform_get_drvdata(pdev);
132 	struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
133 
134 	backlight_device_unregister(bl);
135 	pwm_config(pb->pwm, 0, pb->period);
136 	pwm_disable(pb->pwm);
137 	pwm_free(pb->pwm);
138 	kfree(pb);
139 	if (data->exit)
140 		data->exit(&pdev->dev);
141 	return 0;
142 }
143 
144 #ifdef CONFIG_PM
145 static int pwm_backlight_suspend(struct platform_device *pdev,
146 				 pm_message_t state)
147 {
148 	struct backlight_device *bl = platform_get_drvdata(pdev);
149 	struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
150 
151 	if (pb->notify)
152 		pb->notify(pb->dev, 0);
153 	pwm_config(pb->pwm, 0, pb->period);
154 	pwm_disable(pb->pwm);
155 	return 0;
156 }
157 
158 static int pwm_backlight_resume(struct platform_device *pdev)
159 {
160 	struct backlight_device *bl = platform_get_drvdata(pdev);
161 
162 	backlight_update_status(bl);
163 	return 0;
164 }
165 #else
166 #define pwm_backlight_suspend	NULL
167 #define pwm_backlight_resume	NULL
168 #endif
169 
170 static struct platform_driver pwm_backlight_driver = {
171 	.driver		= {
172 		.name	= "pwm-backlight",
173 		.owner	= THIS_MODULE,
174 	},
175 	.probe		= pwm_backlight_probe,
176 	.remove		= pwm_backlight_remove,
177 	.suspend	= pwm_backlight_suspend,
178 	.resume		= pwm_backlight_resume,
179 };
180 
181 static int __init pwm_backlight_init(void)
182 {
183 	return platform_driver_register(&pwm_backlight_driver);
184 }
185 module_init(pwm_backlight_init);
186 
187 static void __exit pwm_backlight_exit(void)
188 {
189 	platform_driver_unregister(&pwm_backlight_driver);
190 }
191 module_exit(pwm_backlight_exit);
192 
193 MODULE_DESCRIPTION("PWM based Backlight Driver");
194 MODULE_LICENSE("GPL");
195 MODULE_ALIAS("platform:pwm-backlight");
196 
197