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 casts to the PWM id (0/1/2/3 on PXA) 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 unsigned int period; 26 int (*notify)(int brightness); 27 }; 28 29 static int pwm_backlight_update_status(struct backlight_device *bl) 30 { 31 struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev); 32 int brightness = bl->props.brightness; 33 int max = bl->props.max_brightness; 34 35 if (bl->props.power != FB_BLANK_UNBLANK) 36 brightness = 0; 37 38 if (bl->props.fb_blank != FB_BLANK_UNBLANK) 39 brightness = 0; 40 41 if (pb->notify) 42 brightness = pb->notify(brightness); 43 44 if (brightness == 0) { 45 pwm_config(pb->pwm, 0, pb->period); 46 pwm_disable(pb->pwm); 47 } else { 48 pwm_config(pb->pwm, brightness * pb->period / max, pb->period); 49 pwm_enable(pb->pwm); 50 } 51 return 0; 52 } 53 54 static int pwm_backlight_get_brightness(struct backlight_device *bl) 55 { 56 return bl->props.brightness; 57 } 58 59 static struct backlight_ops pwm_backlight_ops = { 60 .update_status = pwm_backlight_update_status, 61 .get_brightness = pwm_backlight_get_brightness, 62 }; 63 64 static int pwm_backlight_probe(struct platform_device *pdev) 65 { 66 struct platform_pwm_backlight_data *data = pdev->dev.platform_data; 67 struct backlight_device *bl; 68 struct pwm_bl_data *pb; 69 int ret; 70 71 if (!data) 72 return -EINVAL; 73 74 if (data->init) { 75 ret = data->init(&pdev->dev); 76 if (ret < 0) 77 return ret; 78 } 79 80 pb = kzalloc(sizeof(*pb), GFP_KERNEL); 81 if (!pb) { 82 ret = -ENOMEM; 83 goto err_alloc; 84 } 85 86 pb->period = data->pwm_period_ns; 87 pb->notify = data->notify; 88 89 pb->pwm = pwm_request(data->pwm_id, "backlight"); 90 if (IS_ERR(pb->pwm)) { 91 dev_err(&pdev->dev, "unable to request PWM for backlight\n"); 92 ret = PTR_ERR(pb->pwm); 93 goto err_pwm; 94 } 95 96 bl = backlight_device_register(pdev->name, &pdev->dev, 97 pb, &pwm_backlight_ops); 98 if (IS_ERR(bl)) { 99 dev_err(&pdev->dev, "failed to register backlight\n"); 100 ret = PTR_ERR(bl); 101 goto err_bl; 102 } 103 104 bl->props.max_brightness = data->max_brightness; 105 bl->props.brightness = data->dft_brightness; 106 backlight_update_status(bl); 107 108 platform_set_drvdata(pdev, bl); 109 return 0; 110 111 err_bl: 112 pwm_free(pb->pwm); 113 err_pwm: 114 kfree(pb); 115 err_alloc: 116 if (data->exit) 117 data->exit(&pdev->dev); 118 return ret; 119 } 120 121 static int pwm_backlight_remove(struct platform_device *pdev) 122 { 123 struct platform_pwm_backlight_data *data = pdev->dev.platform_data; 124 struct backlight_device *bl = platform_get_drvdata(pdev); 125 struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev); 126 127 backlight_device_unregister(bl); 128 pwm_config(pb->pwm, 0, pb->period); 129 pwm_disable(pb->pwm); 130 pwm_free(pb->pwm); 131 kfree(pb); 132 if (data->exit) 133 data->exit(&pdev->dev); 134 return 0; 135 } 136 137 #ifdef CONFIG_PM 138 static int pwm_backlight_suspend(struct platform_device *pdev, 139 pm_message_t state) 140 { 141 struct backlight_device *bl = platform_get_drvdata(pdev); 142 struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev); 143 144 pwm_config(pb->pwm, 0, pb->period); 145 pwm_disable(pb->pwm); 146 return 0; 147 } 148 149 static int pwm_backlight_resume(struct platform_device *pdev) 150 { 151 struct backlight_device *bl = platform_get_drvdata(pdev); 152 153 backlight_update_status(bl); 154 return 0; 155 } 156 #else 157 #define pwm_backlight_suspend NULL 158 #define pwm_backlight_resume NULL 159 #endif 160 161 static struct platform_driver pwm_backlight_driver = { 162 .driver = { 163 .name = "pwm-backlight", 164 .owner = THIS_MODULE, 165 }, 166 .probe = pwm_backlight_probe, 167 .remove = pwm_backlight_remove, 168 .suspend = pwm_backlight_suspend, 169 .resume = pwm_backlight_resume, 170 }; 171 172 static int __init pwm_backlight_init(void) 173 { 174 return platform_driver_register(&pwm_backlight_driver); 175 } 176 module_init(pwm_backlight_init); 177 178 static void __exit pwm_backlight_exit(void) 179 { 180 platform_driver_unregister(&pwm_backlight_driver); 181 } 182 module_exit(pwm_backlight_exit); 183 184 MODULE_DESCRIPTION("PWM based Backlight Driver"); 185 MODULE_LICENSE("GPL"); 186