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