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/gpio.h> 14 #include <linux/of_gpio.h> 15 #include <linux/module.h> 16 #include <linux/kernel.h> 17 #include <linux/init.h> 18 #include <linux/platform_device.h> 19 #include <linux/fb.h> 20 #include <linux/backlight.h> 21 #include <linux/err.h> 22 #include <linux/pwm.h> 23 #include <linux/pwm_backlight.h> 24 #include <linux/regulator/consumer.h> 25 #include <linux/slab.h> 26 27 struct pwm_bl_data { 28 struct pwm_device *pwm; 29 struct device *dev; 30 unsigned int period; 31 unsigned int lth_brightness; 32 unsigned int *levels; 33 bool enabled; 34 struct regulator *power_supply; 35 int enable_gpio; 36 unsigned long enable_gpio_flags; 37 unsigned int scale; 38 int (*notify)(struct device *, 39 int brightness); 40 void (*notify_after)(struct device *, 41 int brightness); 42 int (*check_fb)(struct device *, struct fb_info *); 43 void (*exit)(struct device *); 44 }; 45 46 static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness) 47 { 48 int err; 49 50 if (pb->enabled) 51 return; 52 53 err = regulator_enable(pb->power_supply); 54 if (err < 0) 55 dev_err(pb->dev, "failed to enable power supply\n"); 56 57 if (gpio_is_valid(pb->enable_gpio)) { 58 if (pb->enable_gpio_flags & PWM_BACKLIGHT_GPIO_ACTIVE_LOW) 59 gpio_set_value(pb->enable_gpio, 0); 60 else 61 gpio_set_value(pb->enable_gpio, 1); 62 } 63 64 pwm_enable(pb->pwm); 65 pb->enabled = true; 66 } 67 68 static void pwm_backlight_power_off(struct pwm_bl_data *pb) 69 { 70 if (!pb->enabled) 71 return; 72 73 pwm_config(pb->pwm, 0, pb->period); 74 pwm_disable(pb->pwm); 75 76 if (gpio_is_valid(pb->enable_gpio)) { 77 if (pb->enable_gpio_flags & PWM_BACKLIGHT_GPIO_ACTIVE_LOW) 78 gpio_set_value(pb->enable_gpio, 1); 79 else 80 gpio_set_value(pb->enable_gpio, 0); 81 } 82 83 regulator_disable(pb->power_supply); 84 pb->enabled = false; 85 } 86 87 static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness) 88 { 89 unsigned int lth = pb->lth_brightness; 90 int duty_cycle; 91 92 if (pb->levels) 93 duty_cycle = pb->levels[brightness]; 94 else 95 duty_cycle = brightness; 96 97 return (duty_cycle * (pb->period - lth) / pb->scale) + lth; 98 } 99 100 static int pwm_backlight_update_status(struct backlight_device *bl) 101 { 102 struct pwm_bl_data *pb = bl_get_data(bl); 103 int brightness = bl->props.brightness; 104 int duty_cycle; 105 106 if (bl->props.power != FB_BLANK_UNBLANK || 107 bl->props.fb_blank != FB_BLANK_UNBLANK || 108 bl->props.state & BL_CORE_FBBLANK) 109 brightness = 0; 110 111 if (pb->notify) 112 brightness = pb->notify(pb->dev, brightness); 113 114 if (brightness > 0) { 115 duty_cycle = compute_duty_cycle(pb, brightness); 116 pwm_config(pb->pwm, duty_cycle, pb->period); 117 pwm_backlight_power_on(pb, brightness); 118 } else 119 pwm_backlight_power_off(pb); 120 121 if (pb->notify_after) 122 pb->notify_after(pb->dev, brightness); 123 124 return 0; 125 } 126 127 static int pwm_backlight_get_brightness(struct backlight_device *bl) 128 { 129 return bl->props.brightness; 130 } 131 132 static int pwm_backlight_check_fb(struct backlight_device *bl, 133 struct fb_info *info) 134 { 135 struct pwm_bl_data *pb = bl_get_data(bl); 136 137 return !pb->check_fb || pb->check_fb(pb->dev, info); 138 } 139 140 static const struct backlight_ops pwm_backlight_ops = { 141 .update_status = pwm_backlight_update_status, 142 .get_brightness = pwm_backlight_get_brightness, 143 .check_fb = pwm_backlight_check_fb, 144 }; 145 146 #ifdef CONFIG_OF 147 static int pwm_backlight_parse_dt(struct device *dev, 148 struct platform_pwm_backlight_data *data) 149 { 150 struct device_node *node = dev->of_node; 151 enum of_gpio_flags flags; 152 struct property *prop; 153 int length; 154 u32 value; 155 int ret; 156 157 if (!node) 158 return -ENODEV; 159 160 memset(data, 0, sizeof(*data)); 161 162 /* determine the number of brightness levels */ 163 prop = of_find_property(node, "brightness-levels", &length); 164 if (!prop) 165 return -EINVAL; 166 167 data->max_brightness = length / sizeof(u32); 168 169 /* read brightness levels from DT property */ 170 if (data->max_brightness > 0) { 171 size_t size = sizeof(*data->levels) * data->max_brightness; 172 173 data->levels = devm_kzalloc(dev, size, GFP_KERNEL); 174 if (!data->levels) 175 return -ENOMEM; 176 177 ret = of_property_read_u32_array(node, "brightness-levels", 178 data->levels, 179 data->max_brightness); 180 if (ret < 0) 181 return ret; 182 183 ret = of_property_read_u32(node, "default-brightness-level", 184 &value); 185 if (ret < 0) 186 return ret; 187 188 data->dft_brightness = value; 189 data->max_brightness--; 190 } 191 192 data->enable_gpio = of_get_named_gpio_flags(node, "enable-gpios", 0, 193 &flags); 194 if (data->enable_gpio == -EPROBE_DEFER) 195 return -EPROBE_DEFER; 196 197 if (gpio_is_valid(data->enable_gpio) && (flags & OF_GPIO_ACTIVE_LOW)) 198 data->enable_gpio_flags |= PWM_BACKLIGHT_GPIO_ACTIVE_LOW; 199 200 return 0; 201 } 202 203 static struct of_device_id pwm_backlight_of_match[] = { 204 { .compatible = "pwm-backlight" }, 205 { } 206 }; 207 208 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match); 209 #else 210 static int pwm_backlight_parse_dt(struct device *dev, 211 struct platform_pwm_backlight_data *data) 212 { 213 return -ENODEV; 214 } 215 #endif 216 217 static int pwm_backlight_probe(struct platform_device *pdev) 218 { 219 struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev); 220 struct platform_pwm_backlight_data defdata; 221 struct backlight_properties props; 222 struct backlight_device *bl; 223 struct pwm_bl_data *pb; 224 int ret; 225 226 if (!data) { 227 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata); 228 if (ret < 0) { 229 dev_err(&pdev->dev, "failed to find platform data\n"); 230 return ret; 231 } 232 233 data = &defdata; 234 } 235 236 if (data->init) { 237 ret = data->init(&pdev->dev); 238 if (ret < 0) 239 return ret; 240 } 241 242 pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL); 243 if (!pb) { 244 dev_err(&pdev->dev, "no memory for state\n"); 245 ret = -ENOMEM; 246 goto err_alloc; 247 } 248 249 if (data->levels) { 250 unsigned int i; 251 252 for (i = 0; i <= data->max_brightness; i++) 253 if (data->levels[i] > pb->scale) 254 pb->scale = data->levels[i]; 255 256 pb->levels = data->levels; 257 } else 258 pb->scale = data->max_brightness; 259 260 pb->enable_gpio = data->enable_gpio; 261 pb->enable_gpio_flags = data->enable_gpio_flags; 262 pb->notify = data->notify; 263 pb->notify_after = data->notify_after; 264 pb->check_fb = data->check_fb; 265 pb->exit = data->exit; 266 pb->dev = &pdev->dev; 267 pb->enabled = false; 268 269 if (gpio_is_valid(pb->enable_gpio)) { 270 unsigned long flags; 271 272 if (pb->enable_gpio_flags & PWM_BACKLIGHT_GPIO_ACTIVE_LOW) 273 flags = GPIOF_OUT_INIT_HIGH; 274 else 275 flags = GPIOF_OUT_INIT_LOW; 276 277 ret = gpio_request_one(pb->enable_gpio, flags, "enable"); 278 if (ret < 0) { 279 dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n", 280 pb->enable_gpio, ret); 281 goto err_alloc; 282 } 283 } 284 285 pb->power_supply = devm_regulator_get(&pdev->dev, "power"); 286 if (IS_ERR(pb->power_supply)) { 287 ret = PTR_ERR(pb->power_supply); 288 goto err_gpio; 289 } 290 291 pb->pwm = devm_pwm_get(&pdev->dev, NULL); 292 if (IS_ERR(pb->pwm)) { 293 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n"); 294 295 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight"); 296 if (IS_ERR(pb->pwm)) { 297 dev_err(&pdev->dev, "unable to request legacy PWM\n"); 298 ret = PTR_ERR(pb->pwm); 299 goto err_gpio; 300 } 301 } 302 303 dev_dbg(&pdev->dev, "got pwm for backlight\n"); 304 305 /* 306 * The DT case will set the pwm_period_ns field to 0 and store the 307 * period, parsed from the DT, in the PWM device. For the non-DT case, 308 * set the period from platform data. 309 */ 310 if (data->pwm_period_ns > 0) 311 pwm_set_period(pb->pwm, data->pwm_period_ns); 312 313 pb->period = pwm_get_period(pb->pwm); 314 pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale); 315 316 memset(&props, 0, sizeof(struct backlight_properties)); 317 props.type = BACKLIGHT_RAW; 318 props.max_brightness = data->max_brightness; 319 bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb, 320 &pwm_backlight_ops, &props); 321 if (IS_ERR(bl)) { 322 dev_err(&pdev->dev, "failed to register backlight\n"); 323 ret = PTR_ERR(bl); 324 goto err_gpio; 325 } 326 327 if (data->dft_brightness > data->max_brightness) { 328 dev_warn(&pdev->dev, 329 "invalid default brightness level: %u, using %u\n", 330 data->dft_brightness, data->max_brightness); 331 data->dft_brightness = data->max_brightness; 332 } 333 334 bl->props.brightness = data->dft_brightness; 335 backlight_update_status(bl); 336 337 platform_set_drvdata(pdev, bl); 338 return 0; 339 340 err_gpio: 341 if (gpio_is_valid(pb->enable_gpio)) 342 gpio_free(pb->enable_gpio); 343 err_alloc: 344 if (data->exit) 345 data->exit(&pdev->dev); 346 return ret; 347 } 348 349 static int pwm_backlight_remove(struct platform_device *pdev) 350 { 351 struct backlight_device *bl = platform_get_drvdata(pdev); 352 struct pwm_bl_data *pb = bl_get_data(bl); 353 354 backlight_device_unregister(bl); 355 pwm_backlight_power_off(pb); 356 357 if (pb->exit) 358 pb->exit(&pdev->dev); 359 360 return 0; 361 } 362 363 #ifdef CONFIG_PM_SLEEP 364 static int pwm_backlight_suspend(struct device *dev) 365 { 366 struct backlight_device *bl = dev_get_drvdata(dev); 367 struct pwm_bl_data *pb = bl_get_data(bl); 368 369 if (pb->notify) 370 pb->notify(pb->dev, 0); 371 372 pwm_backlight_power_off(pb); 373 374 if (pb->notify_after) 375 pb->notify_after(pb->dev, 0); 376 377 return 0; 378 } 379 380 static int pwm_backlight_resume(struct device *dev) 381 { 382 struct backlight_device *bl = dev_get_drvdata(dev); 383 384 backlight_update_status(bl); 385 386 return 0; 387 } 388 #endif 389 390 static const struct dev_pm_ops pwm_backlight_pm_ops = { 391 #ifdef CONFIG_PM_SLEEP 392 .suspend = pwm_backlight_suspend, 393 .resume = pwm_backlight_resume, 394 .poweroff = pwm_backlight_suspend, 395 .restore = pwm_backlight_resume, 396 #endif 397 }; 398 399 static struct platform_driver pwm_backlight_driver = { 400 .driver = { 401 .name = "pwm-backlight", 402 .owner = THIS_MODULE, 403 .pm = &pwm_backlight_pm_ops, 404 .of_match_table = of_match_ptr(pwm_backlight_of_match), 405 }, 406 .probe = pwm_backlight_probe, 407 .remove = pwm_backlight_remove, 408 }; 409 410 module_platform_driver(pwm_backlight_driver); 411 412 MODULE_DESCRIPTION("PWM based Backlight Driver"); 413 MODULE_LICENSE("GPL"); 414 MODULE_ALIAS("platform:pwm-backlight"); 415