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 dev_err(&pdev->dev, "failed to find platform data\n"); 73 return -EINVAL; 74 } 75 76 if (data->init) { 77 ret = data->init(&pdev->dev); 78 if (ret < 0) 79 return ret; 80 } 81 82 pb = kzalloc(sizeof(*pb), GFP_KERNEL); 83 if (!pb) { 84 dev_err(&pdev->dev, "no memory for state\n"); 85 ret = -ENOMEM; 86 goto err_alloc; 87 } 88 89 pb->period = data->pwm_period_ns; 90 pb->notify = data->notify; 91 92 pb->pwm = pwm_request(data->pwm_id, "backlight"); 93 if (IS_ERR(pb->pwm)) { 94 dev_err(&pdev->dev, "unable to request PWM for backlight\n"); 95 ret = PTR_ERR(pb->pwm); 96 goto err_pwm; 97 } else 98 dev_dbg(&pdev->dev, "got pwm for backlight\n"); 99 100 bl = backlight_device_register(pdev->name, &pdev->dev, 101 pb, &pwm_backlight_ops); 102 if (IS_ERR(bl)) { 103 dev_err(&pdev->dev, "failed to register backlight\n"); 104 ret = PTR_ERR(bl); 105 goto err_bl; 106 } 107 108 bl->props.max_brightness = data->max_brightness; 109 bl->props.brightness = data->dft_brightness; 110 backlight_update_status(bl); 111 112 platform_set_drvdata(pdev, bl); 113 return 0; 114 115 err_bl: 116 pwm_free(pb->pwm); 117 err_pwm: 118 kfree(pb); 119 err_alloc: 120 if (data->exit) 121 data->exit(&pdev->dev); 122 return ret; 123 } 124 125 static int pwm_backlight_remove(struct platform_device *pdev) 126 { 127 struct platform_pwm_backlight_data *data = pdev->dev.platform_data; 128 struct backlight_device *bl = platform_get_drvdata(pdev); 129 struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev); 130 131 backlight_device_unregister(bl); 132 pwm_config(pb->pwm, 0, pb->period); 133 pwm_disable(pb->pwm); 134 pwm_free(pb->pwm); 135 kfree(pb); 136 if (data->exit) 137 data->exit(&pdev->dev); 138 return 0; 139 } 140 141 #ifdef CONFIG_PM 142 static int pwm_backlight_suspend(struct platform_device *pdev, 143 pm_message_t state) 144 { 145 struct backlight_device *bl = platform_get_drvdata(pdev); 146 struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev); 147 148 pwm_config(pb->pwm, 0, pb->period); 149 pwm_disable(pb->pwm); 150 return 0; 151 } 152 153 static int pwm_backlight_resume(struct platform_device *pdev) 154 { 155 struct backlight_device *bl = platform_get_drvdata(pdev); 156 157 backlight_update_status(bl); 158 return 0; 159 } 160 #else 161 #define pwm_backlight_suspend NULL 162 #define pwm_backlight_resume NULL 163 #endif 164 165 static struct platform_driver pwm_backlight_driver = { 166 .driver = { 167 .name = "pwm-backlight", 168 .owner = THIS_MODULE, 169 }, 170 .probe = pwm_backlight_probe, 171 .remove = pwm_backlight_remove, 172 .suspend = pwm_backlight_suspend, 173 .resume = pwm_backlight_resume, 174 }; 175 176 static int __init pwm_backlight_init(void) 177 { 178 return platform_driver_register(&pwm_backlight_driver); 179 } 180 module_init(pwm_backlight_init); 181 182 static void __exit pwm_backlight_exit(void) 183 { 184 platform_driver_unregister(&pwm_backlight_driver); 185 } 186 module_exit(pwm_backlight_exit); 187 188 MODULE_DESCRIPTION("PWM based Backlight Driver"); 189 MODULE_LICENSE("GPL"); 190 MODULE_ALIAS("platform:pwm-backlight"); 191 192