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
*,
33 static int pwm_backlight_update_status(struct backlight_device
*bl
)
35 struct pwm_bl_data
*pb
= dev_get_drvdata(&bl
->dev
);
36 int brightness
= bl
->props
.brightness
;
37 int max
= bl
->props
.max_brightness
;
39 if (bl
->props
.power
!= FB_BLANK_UNBLANK
)
42 if (bl
->props
.fb_blank
!= FB_BLANK_UNBLANK
)
46 brightness
= pb
->notify(pb
->dev
, brightness
);
48 if (brightness
== 0) {
49 pwm_config(pb
->pwm
, 0, pb
->period
);
52 brightness
= pb
->lth_brightness
+
53 (brightness
* (pb
->period
- pb
->lth_brightness
) / max
);
54 pwm_config(pb
->pwm
, brightness
, pb
->period
);
60 static int pwm_backlight_get_brightness(struct backlight_device
*bl
)
62 return bl
->props
.brightness
;
65 static const struct backlight_ops pwm_backlight_ops
= {
66 .update_status
= pwm_backlight_update_status
,
67 .get_brightness
= pwm_backlight_get_brightness
,
70 static int pwm_backlight_probe(struct platform_device
*pdev
)
72 struct backlight_properties props
;
73 struct platform_pwm_backlight_data
*data
= pdev
->dev
.platform_data
;
74 struct backlight_device
*bl
;
75 struct pwm_bl_data
*pb
;
79 dev_err(&pdev
->dev
, "failed to find platform data\n");
84 ret
= data
->init(&pdev
->dev
);
89 pb
= kzalloc(sizeof(*pb
), GFP_KERNEL
);
91 dev_err(&pdev
->dev
, "no memory for state\n");
96 pb
->period
= data
->pwm_period_ns
;
97 pb
->notify
= data
->notify
;
98 pb
->lth_brightness
= data
->lth_brightness
*
99 (data
->pwm_period_ns
/ data
->max_brightness
);
100 pb
->dev
= &pdev
->dev
;
102 pb
->pwm
= pwm_request(data
->pwm_id
, "backlight");
103 if (IS_ERR(pb
->pwm
)) {
104 dev_err(&pdev
->dev
, "unable to request PWM for backlight\n");
105 ret
= PTR_ERR(pb
->pwm
);
108 dev_dbg(&pdev
->dev
, "got pwm for backlight\n");
110 memset(&props
, 0, sizeof(struct backlight_properties
));
111 props
.max_brightness
= data
->max_brightness
;
112 bl
= backlight_device_register(dev_name(&pdev
->dev
), &pdev
->dev
, pb
,
113 &pwm_backlight_ops
, &props
);
115 dev_err(&pdev
->dev
, "failed to register backlight\n");
120 bl
->props
.brightness
= data
->dft_brightness
;
121 backlight_update_status(bl
);
123 platform_set_drvdata(pdev
, bl
);
132 data
->exit(&pdev
->dev
);
136 static int pwm_backlight_remove(struct platform_device
*pdev
)
138 struct platform_pwm_backlight_data
*data
= pdev
->dev
.platform_data
;
139 struct backlight_device
*bl
= platform_get_drvdata(pdev
);
140 struct pwm_bl_data
*pb
= dev_get_drvdata(&bl
->dev
);
142 backlight_device_unregister(bl
);
143 pwm_config(pb
->pwm
, 0, pb
->period
);
144 pwm_disable(pb
->pwm
);
148 data
->exit(&pdev
->dev
);
153 static int pwm_backlight_suspend(struct platform_device
*pdev
,
156 struct backlight_device
*bl
= platform_get_drvdata(pdev
);
157 struct pwm_bl_data
*pb
= dev_get_drvdata(&bl
->dev
);
160 pb
->notify(pb
->dev
, 0);
161 pwm_config(pb
->pwm
, 0, pb
->period
);
162 pwm_disable(pb
->pwm
);
166 static int pwm_backlight_resume(struct platform_device
*pdev
)
168 struct backlight_device
*bl
= platform_get_drvdata(pdev
);
170 backlight_update_status(bl
);
174 #define pwm_backlight_suspend NULL
175 #define pwm_backlight_resume NULL
178 static struct platform_driver pwm_backlight_driver
= {
180 .name
= "pwm-backlight",
181 .owner
= THIS_MODULE
,
183 .probe
= pwm_backlight_probe
,
184 .remove
= pwm_backlight_remove
,
185 .suspend
= pwm_backlight_suspend
,
186 .resume
= pwm_backlight_resume
,
189 static int __init
pwm_backlight_init(void)
191 return platform_driver_register(&pwm_backlight_driver
);
193 module_init(pwm_backlight_init
);
195 static void __exit
pwm_backlight_exit(void)
197 platform_driver_unregister(&pwm_backlight_driver
);
199 module_exit(pwm_backlight_exit
);
201 MODULE_DESCRIPTION("PWM based Backlight Driver");
202 MODULE_LICENSE("GPL");
203 MODULE_ALIAS("platform:pwm-backlight");