2 * linux/drivers/video/backlight/pwm_bl.c
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
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.
13 #include <linux/module.h>
14 #include <linux/kernel.h>
15 #include <linux/init.h>
16 #include <linux/platform_device.h>
18 #include <linux/backlight.h>
19 #include <linux/err.h>
20 #include <linux/pwm.h>
21 #include <linux/pwm_backlight.h>
22 #include <linux/slab.h>
25 struct pwm_device *pwm;
28 unsigned int lth_brightness;
29 int (*notify)(struct device *,
31 void (*notify_after)(struct device *,
33 int (*check_fb)(struct device *, struct fb_info *);
36 static int pwm_backlight_update_status(struct backlight_device *bl)
38 struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
39 int brightness = bl->props.brightness;
40 int max = bl->props.max_brightness;
42 if (bl->props.power != FB_BLANK_UNBLANK)
45 if (bl->props.fb_blank != FB_BLANK_UNBLANK)
49 brightness = pb->notify(pb->dev, brightness);
51 if (brightness == 0) {
52 pwm_config(pb->pwm, 0, pb->period);
55 brightness = pb->lth_brightness +
56 (brightness * (pb->period - pb->lth_brightness) / max);
57 pwm_config(pb->pwm, brightness, pb->period);
62 pb->notify_after(pb->dev, brightness);
67 static int pwm_backlight_get_brightness(struct backlight_device *bl)
69 return bl->props.brightness;
72 static int pwm_backlight_check_fb(struct backlight_device *bl,
75 struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
77 return !pb->check_fb || pb->check_fb(pb->dev, info);
80 static const struct backlight_ops pwm_backlight_ops = {
81 .update_status = pwm_backlight_update_status,
82 .get_brightness = pwm_backlight_get_brightness,
83 .check_fb = pwm_backlight_check_fb,
86 static int pwm_backlight_probe(struct platform_device *pdev)
88 struct backlight_properties props;
89 struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
90 struct backlight_device *bl;
91 struct pwm_bl_data *pb;
95 dev_err(&pdev->dev, "failed to find platform data\n");
100 ret = data->init(&pdev->dev);
105 pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
107 dev_err(&pdev->dev, "no memory for state\n");
112 pb->period = data->pwm_period_ns;
113 pb->notify = data->notify;
114 pb->notify_after = data->notify_after;
115 pb->check_fb = data->check_fb;
116 pb->lth_brightness = data->lth_brightness *
117 (data->pwm_period_ns / data->max_brightness);
118 pb->dev = &pdev->dev;
120 pb->pwm = pwm_request(data->pwm_id, "backlight");
121 if (IS_ERR(pb->pwm)) {
122 dev_err(&pdev->dev, "unable to request PWM for backlight\n");
123 ret = PTR_ERR(pb->pwm);
126 dev_dbg(&pdev->dev, "got pwm for backlight\n");
128 memset(&props, 0, sizeof(struct backlight_properties));
129 props.type = BACKLIGHT_RAW;
130 props.max_brightness = data->max_brightness;
131 bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
132 &pwm_backlight_ops, &props);
134 dev_err(&pdev->dev, "failed to register backlight\n");
139 bl->props.brightness = data->dft_brightness;
140 backlight_update_status(bl);
142 platform_set_drvdata(pdev, bl);
149 data->exit(&pdev->dev);
153 static int pwm_backlight_remove(struct platform_device *pdev)
155 struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
156 struct backlight_device *bl = platform_get_drvdata(pdev);
157 struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
159 backlight_device_unregister(bl);
160 pwm_config(pb->pwm, 0, pb->period);
161 pwm_disable(pb->pwm);
164 data->exit(&pdev->dev);
169 static int pwm_backlight_suspend(struct device *dev)
171 struct backlight_device *bl = dev_get_drvdata(dev);
172 struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
175 pb->notify(pb->dev, 0);
176 pwm_config(pb->pwm, 0, pb->period);
177 pwm_disable(pb->pwm);
178 if (pb->notify_after)
179 pb->notify_after(pb->dev, 0);
183 static int pwm_backlight_resume(struct device *dev)
185 struct backlight_device *bl = dev_get_drvdata(dev);
187 backlight_update_status(bl);
191 static SIMPLE_DEV_PM_OPS(pwm_backlight_pm_ops, pwm_backlight_suspend,
192 pwm_backlight_resume);
196 static struct platform_driver pwm_backlight_driver = {
198 .name = "pwm-backlight",
199 .owner = THIS_MODULE,
201 .pm = &pwm_backlight_pm_ops,
204 .probe = pwm_backlight_probe,
205 .remove = pwm_backlight_remove,
208 module_platform_driver(pwm_backlight_driver);
210 MODULE_DESCRIPTION("PWM based Backlight Driver");
211 MODULE_LICENSE("GPL");
212 MODULE_ALIAS("platform:pwm-backlight");