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 #include <linux/slab.h> 23 24 struct pwm_bl_data { 25 struct pwm_device *pwm; 26 struct device *dev; 27 unsigned int period; 28 unsigned int lth_brightness; 29 int (*notify)(struct device *, 30 int brightness); 31 int (*check_fb)(struct device *, struct fb_info *); 32 }; 33 34 static int pwm_backlight_update_status(struct backlight_device *bl) 35 { 36 struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev); 37 int brightness = bl->props.brightness; 38 int max = bl->props.max_brightness; 39 40 if (bl->props.power != FB_BLANK_UNBLANK) 41 brightness = 0; 42 43 if (bl->props.fb_blank != FB_BLANK_UNBLANK) 44 brightness = 0; 45 46 if (pb->notify) 47 brightness = pb->notify(pb->dev, brightness); 48 49 if (brightness == 0) { 50 pwm_config(pb->pwm, 0, pb->period); 51 pwm_disable(pb->pwm); 52 } else { 53 brightness = pb->lth_brightness + 54 (brightness * (pb->period - pb->lth_brightness) / max); 55 pwm_config(pb->pwm, brightness, pb->period); 56 pwm_enable(pb->pwm); 57 } 58 return 0; 59 } 60 61 static int pwm_backlight_get_brightness(struct backlight_device *bl) 62 { 63 return bl->props.brightness; 64 } 65 66 static int pwm_backlight_check_fb(struct backlight_device *bl, 67 struct fb_info *info) 68 { 69 struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev); 70 71 return !pb->check_fb || pb->check_fb(pb->dev, info); 72 } 73 74 static const struct backlight_ops pwm_backlight_ops = { 75 .update_status = pwm_backlight_update_status, 76 .get_brightness = pwm_backlight_get_brightness, 77 .check_fb = pwm_backlight_check_fb, 78 }; 79 80 static int pwm_backlight_probe(struct platform_device *pdev) 81 { 82 struct backlight_properties props; 83 struct platform_pwm_backlight_data *data = pdev->dev.platform_data; 84 struct backlight_device *bl; 85 struct pwm_bl_data *pb; 86 int ret; 87 88 if (!data) { 89 dev_err(&pdev->dev, "failed to find platform data\n"); 90 return -EINVAL; 91 } 92 93 if (data->init) { 94 ret = data->init(&pdev->dev); 95 if (ret < 0) 96 return ret; 97 } 98 99 pb = kzalloc(sizeof(*pb), GFP_KERNEL); 100 if (!pb) { 101 dev_err(&pdev->dev, "no memory for state\n"); 102 ret = -ENOMEM; 103 goto err_alloc; 104 } 105 106 pb->period = data->pwm_period_ns; 107 pb->notify = data->notify; 108 pb->check_fb = data->check_fb; 109 pb->lth_brightness = data->lth_brightness * 110 (data->pwm_period_ns / data->max_brightness); 111 pb->dev = &pdev->dev; 112 113 pb->pwm = pwm_request(data->pwm_id, "backlight"); 114 if (IS_ERR(pb->pwm)) { 115 dev_err(&pdev->dev, "unable to request PWM for backlight\n"); 116 ret = PTR_ERR(pb->pwm); 117 goto err_pwm; 118 } else 119 dev_dbg(&pdev->dev, "got pwm for backlight\n"); 120 121 memset(&props, 0, sizeof(struct backlight_properties)); 122 props.type = BACKLIGHT_RAW; 123 props.max_brightness = data->max_brightness; 124 bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb, 125 &pwm_backlight_ops, &props); 126 if (IS_ERR(bl)) { 127 dev_err(&pdev->dev, "failed to register backlight\n"); 128 ret = PTR_ERR(bl); 129 goto err_bl; 130 } 131 132 bl->props.brightness = data->dft_brightness; 133 backlight_update_status(bl); 134 135 platform_set_drvdata(pdev, bl); 136 return 0; 137 138 err_bl: 139 pwm_free(pb->pwm); 140 err_pwm: 141 kfree(pb); 142 err_alloc: 143 if (data->exit) 144 data->exit(&pdev->dev); 145 return ret; 146 } 147 148 static int pwm_backlight_remove(struct platform_device *pdev) 149 { 150 struct platform_pwm_backlight_data *data = pdev->dev.platform_data; 151 struct backlight_device *bl = platform_get_drvdata(pdev); 152 struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev); 153 154 backlight_device_unregister(bl); 155 pwm_config(pb->pwm, 0, pb->period); 156 pwm_disable(pb->pwm); 157 pwm_free(pb->pwm); 158 kfree(pb); 159 if (data->exit) 160 data->exit(&pdev->dev); 161 return 0; 162 } 163 164 #ifdef CONFIG_PM 165 static int pwm_backlight_suspend(struct platform_device *pdev, 166 pm_message_t state) 167 { 168 struct backlight_device *bl = platform_get_drvdata(pdev); 169 struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev); 170 171 if (pb->notify) 172 pb->notify(pb->dev, 0); 173 pwm_config(pb->pwm, 0, pb->period); 174 pwm_disable(pb->pwm); 175 return 0; 176 } 177 178 static int pwm_backlight_resume(struct platform_device *pdev) 179 { 180 struct backlight_device *bl = platform_get_drvdata(pdev); 181 182 backlight_update_status(bl); 183 return 0; 184 } 185 #else 186 #define pwm_backlight_suspend NULL 187 #define pwm_backlight_resume NULL 188 #endif 189 190 static struct platform_driver pwm_backlight_driver = { 191 .driver = { 192 .name = "pwm-backlight", 193 .owner = THIS_MODULE, 194 }, 195 .probe = pwm_backlight_probe, 196 .remove = pwm_backlight_remove, 197 .suspend = pwm_backlight_suspend, 198 .resume = pwm_backlight_resume, 199 }; 200 201 static int __init pwm_backlight_init(void) 202 { 203 return platform_driver_register(&pwm_backlight_driver); 204 } 205 module_init(pwm_backlight_init); 206 207 static void __exit pwm_backlight_exit(void) 208 { 209 platform_driver_unregister(&pwm_backlight_driver); 210 } 211 module_exit(pwm_backlight_exit); 212 213 MODULE_DESCRIPTION("PWM based Backlight Driver"); 214 MODULE_LICENSE("GPL"); 215 MODULE_ALIAS("platform:pwm-backlight"); 216 217