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/consumer.h> 14 #include <linux/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 struct gpio_desc *enable_gpio; 36 unsigned int scale; 37 bool legacy; 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 (pb->enable_gpio) 58 gpiod_set_value_cansleep(pb->enable_gpio, 1); 59 60 pwm_enable(pb->pwm); 61 pb->enabled = true; 62 } 63 64 static void pwm_backlight_power_off(struct pwm_bl_data *pb) 65 { 66 if (!pb->enabled) 67 return; 68 69 pwm_config(pb->pwm, 0, pb->period); 70 pwm_disable(pb->pwm); 71 72 if (pb->enable_gpio) 73 gpiod_set_value_cansleep(pb->enable_gpio, 0); 74 75 regulator_disable(pb->power_supply); 76 pb->enabled = false; 77 } 78 79 static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness) 80 { 81 unsigned int lth = pb->lth_brightness; 82 int duty_cycle; 83 84 if (pb->levels) 85 duty_cycle = pb->levels[brightness]; 86 else 87 duty_cycle = brightness; 88 89 return (duty_cycle * (pb->period - lth) / pb->scale) + lth; 90 } 91 92 static int pwm_backlight_update_status(struct backlight_device *bl) 93 { 94 struct pwm_bl_data *pb = bl_get_data(bl); 95 int brightness = bl->props.brightness; 96 int duty_cycle; 97 98 if (bl->props.power != FB_BLANK_UNBLANK || 99 bl->props.fb_blank != FB_BLANK_UNBLANK || 100 bl->props.state & BL_CORE_FBBLANK) 101 brightness = 0; 102 103 if (pb->notify) 104 brightness = pb->notify(pb->dev, brightness); 105 106 if (brightness > 0) { 107 duty_cycle = compute_duty_cycle(pb, brightness); 108 pwm_config(pb->pwm, duty_cycle, pb->period); 109 pwm_backlight_power_on(pb, brightness); 110 } else 111 pwm_backlight_power_off(pb); 112 113 if (pb->notify_after) 114 pb->notify_after(pb->dev, brightness); 115 116 return 0; 117 } 118 119 static int pwm_backlight_check_fb(struct backlight_device *bl, 120 struct fb_info *info) 121 { 122 struct pwm_bl_data *pb = bl_get_data(bl); 123 124 return !pb->check_fb || pb->check_fb(pb->dev, info); 125 } 126 127 static const struct backlight_ops pwm_backlight_ops = { 128 .update_status = pwm_backlight_update_status, 129 .check_fb = pwm_backlight_check_fb, 130 }; 131 132 #ifdef CONFIG_OF 133 static int pwm_backlight_parse_dt(struct device *dev, 134 struct platform_pwm_backlight_data *data) 135 { 136 struct device_node *node = dev->of_node; 137 struct property *prop; 138 int length; 139 u32 value; 140 int ret; 141 142 if (!node) 143 return -ENODEV; 144 145 memset(data, 0, sizeof(*data)); 146 147 /* determine the number of brightness levels */ 148 prop = of_find_property(node, "brightness-levels", &length); 149 if (!prop) 150 return -EINVAL; 151 152 data->max_brightness = length / sizeof(u32); 153 154 /* read brightness levels from DT property */ 155 if (data->max_brightness > 0) { 156 size_t size = sizeof(*data->levels) * data->max_brightness; 157 158 data->levels = devm_kzalloc(dev, size, GFP_KERNEL); 159 if (!data->levels) 160 return -ENOMEM; 161 162 ret = of_property_read_u32_array(node, "brightness-levels", 163 data->levels, 164 data->max_brightness); 165 if (ret < 0) 166 return ret; 167 168 ret = of_property_read_u32(node, "default-brightness-level", 169 &value); 170 if (ret < 0) 171 return ret; 172 173 data->dft_brightness = value; 174 data->max_brightness--; 175 } 176 177 data->enable_gpio = -EINVAL; 178 return 0; 179 } 180 181 static const struct of_device_id pwm_backlight_of_match[] = { 182 { .compatible = "pwm-backlight" }, 183 { } 184 }; 185 186 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match); 187 #else 188 static int pwm_backlight_parse_dt(struct device *dev, 189 struct platform_pwm_backlight_data *data) 190 { 191 return -ENODEV; 192 } 193 #endif 194 195 static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb) 196 { 197 struct device_node *node = pb->dev->of_node; 198 199 /* Not booted with device tree or no phandle link to the node */ 200 if (!node || !node->phandle) 201 return FB_BLANK_UNBLANK; 202 203 /* 204 * If the driver is probed from the device tree and there is a 205 * phandle link pointing to the backlight node, it is safe to 206 * assume that another driver will enable the backlight at the 207 * appropriate time. Therefore, if it is disabled, keep it so. 208 */ 209 210 /* if the enable GPIO is disabled, do not enable the backlight */ 211 if (pb->enable_gpio && gpiod_get_value(pb->enable_gpio) == 0) 212 return FB_BLANK_POWERDOWN; 213 214 /* The regulator is disabled, do not enable the backlight */ 215 if (!regulator_is_enabled(pb->power_supply)) 216 return FB_BLANK_POWERDOWN; 217 218 /* The PWM is disabled, keep it like this */ 219 if (!pwm_is_enabled(pb->pwm)) 220 return FB_BLANK_POWERDOWN; 221 222 return FB_BLANK_UNBLANK; 223 } 224 225 static int pwm_backlight_probe(struct platform_device *pdev) 226 { 227 struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev); 228 struct platform_pwm_backlight_data defdata; 229 struct backlight_properties props; 230 struct backlight_device *bl; 231 struct device_node *node = pdev->dev.of_node; 232 struct pwm_bl_data *pb; 233 struct pwm_args pargs; 234 int ret; 235 236 if (!data) { 237 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata); 238 if (ret < 0) { 239 dev_err(&pdev->dev, "failed to find platform data\n"); 240 return ret; 241 } 242 243 data = &defdata; 244 } 245 246 if (data->init) { 247 ret = data->init(&pdev->dev); 248 if (ret < 0) 249 return ret; 250 } 251 252 pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL); 253 if (!pb) { 254 ret = -ENOMEM; 255 goto err_alloc; 256 } 257 258 if (data->levels) { 259 unsigned int i; 260 261 for (i = 0; i <= data->max_brightness; i++) 262 if (data->levels[i] > pb->scale) 263 pb->scale = data->levels[i]; 264 265 pb->levels = data->levels; 266 } else 267 pb->scale = data->max_brightness; 268 269 pb->notify = data->notify; 270 pb->notify_after = data->notify_after; 271 pb->check_fb = data->check_fb; 272 pb->exit = data->exit; 273 pb->dev = &pdev->dev; 274 pb->enabled = false; 275 276 pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable", 277 GPIOD_ASIS); 278 if (IS_ERR(pb->enable_gpio)) { 279 ret = PTR_ERR(pb->enable_gpio); 280 goto err_alloc; 281 } 282 283 /* 284 * Compatibility fallback for drivers still using the integer GPIO 285 * platform data. Must go away soon. 286 */ 287 if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) { 288 ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio, 289 GPIOF_OUT_INIT_HIGH, "enable"); 290 if (ret < 0) { 291 dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n", 292 data->enable_gpio, ret); 293 goto err_alloc; 294 } 295 296 pb->enable_gpio = gpio_to_desc(data->enable_gpio); 297 } 298 299 /* 300 * If the GPIO is not known to be already configured as output, that 301 * is, if gpiod_get_direction returns either GPIOF_DIR_IN or -EINVAL, 302 * change the direction to output and set the GPIO as active. 303 * Do not force the GPIO to active when it was already output as it 304 * could cause backlight flickering or we would enable the backlight too 305 * early. Leave the decision of the initial backlight state for later. 306 */ 307 if (pb->enable_gpio && 308 gpiod_get_direction(pb->enable_gpio) != GPIOF_DIR_OUT) 309 gpiod_direction_output(pb->enable_gpio, 1); 310 311 pb->power_supply = devm_regulator_get(&pdev->dev, "power"); 312 if (IS_ERR(pb->power_supply)) { 313 ret = PTR_ERR(pb->power_supply); 314 goto err_alloc; 315 } 316 317 pb->pwm = devm_pwm_get(&pdev->dev, NULL); 318 if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) { 319 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n"); 320 pb->legacy = true; 321 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight"); 322 } 323 324 if (IS_ERR(pb->pwm)) { 325 ret = PTR_ERR(pb->pwm); 326 if (ret != -EPROBE_DEFER) 327 dev_err(&pdev->dev, "unable to request PWM\n"); 328 goto err_alloc; 329 } 330 331 dev_dbg(&pdev->dev, "got pwm for backlight\n"); 332 333 /* 334 * FIXME: pwm_apply_args() should be removed when switching to 335 * the atomic PWM API. 336 */ 337 pwm_apply_args(pb->pwm); 338 339 /* 340 * The DT case will set the pwm_period_ns field to 0 and store the 341 * period, parsed from the DT, in the PWM device. For the non-DT case, 342 * set the period from platform data if it has not already been set 343 * via the PWM lookup table. 344 */ 345 pwm_get_args(pb->pwm, &pargs); 346 pb->period = pargs.period; 347 if (!pb->period && (data->pwm_period_ns > 0)) 348 pb->period = data->pwm_period_ns; 349 350 pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale); 351 352 memset(&props, 0, sizeof(struct backlight_properties)); 353 props.type = BACKLIGHT_RAW; 354 props.max_brightness = data->max_brightness; 355 bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb, 356 &pwm_backlight_ops, &props); 357 if (IS_ERR(bl)) { 358 dev_err(&pdev->dev, "failed to register backlight\n"); 359 ret = PTR_ERR(bl); 360 if (pb->legacy) 361 pwm_free(pb->pwm); 362 goto err_alloc; 363 } 364 365 if (data->dft_brightness > data->max_brightness) { 366 dev_warn(&pdev->dev, 367 "invalid default brightness level: %u, using %u\n", 368 data->dft_brightness, data->max_brightness); 369 data->dft_brightness = data->max_brightness; 370 } 371 372 bl->props.brightness = data->dft_brightness; 373 bl->props.power = pwm_backlight_initial_power_state(pb); 374 backlight_update_status(bl); 375 376 platform_set_drvdata(pdev, bl); 377 return 0; 378 379 err_alloc: 380 if (data->exit) 381 data->exit(&pdev->dev); 382 return ret; 383 } 384 385 static int pwm_backlight_remove(struct platform_device *pdev) 386 { 387 struct backlight_device *bl = platform_get_drvdata(pdev); 388 struct pwm_bl_data *pb = bl_get_data(bl); 389 390 backlight_device_unregister(bl); 391 pwm_backlight_power_off(pb); 392 393 if (pb->exit) 394 pb->exit(&pdev->dev); 395 if (pb->legacy) 396 pwm_free(pb->pwm); 397 398 return 0; 399 } 400 401 static void pwm_backlight_shutdown(struct platform_device *pdev) 402 { 403 struct backlight_device *bl = platform_get_drvdata(pdev); 404 struct pwm_bl_data *pb = bl_get_data(bl); 405 406 pwm_backlight_power_off(pb); 407 } 408 409 #ifdef CONFIG_PM_SLEEP 410 static int pwm_backlight_suspend(struct device *dev) 411 { 412 struct backlight_device *bl = dev_get_drvdata(dev); 413 struct pwm_bl_data *pb = bl_get_data(bl); 414 415 if (pb->notify) 416 pb->notify(pb->dev, 0); 417 418 pwm_backlight_power_off(pb); 419 420 if (pb->notify_after) 421 pb->notify_after(pb->dev, 0); 422 423 return 0; 424 } 425 426 static int pwm_backlight_resume(struct device *dev) 427 { 428 struct backlight_device *bl = dev_get_drvdata(dev); 429 430 backlight_update_status(bl); 431 432 return 0; 433 } 434 #endif 435 436 static const struct dev_pm_ops pwm_backlight_pm_ops = { 437 #ifdef CONFIG_PM_SLEEP 438 .suspend = pwm_backlight_suspend, 439 .resume = pwm_backlight_resume, 440 .poweroff = pwm_backlight_suspend, 441 .restore = pwm_backlight_resume, 442 #endif 443 }; 444 445 static struct platform_driver pwm_backlight_driver = { 446 .driver = { 447 .name = "pwm-backlight", 448 .pm = &pwm_backlight_pm_ops, 449 .of_match_table = of_match_ptr(pwm_backlight_of_match), 450 }, 451 .probe = pwm_backlight_probe, 452 .remove = pwm_backlight_remove, 453 .shutdown = pwm_backlight_shutdown, 454 }; 455 456 module_platform_driver(pwm_backlight_driver); 457 458 MODULE_DESCRIPTION("PWM based Backlight Driver"); 459 MODULE_LICENSE("GPL"); 460 MODULE_ALIAS("platform:pwm-backlight"); 461