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(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(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 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_probe(struct platform_device *pdev) 196 { 197 struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev); 198 struct platform_pwm_backlight_data defdata; 199 struct backlight_properties props; 200 struct backlight_device *bl; 201 struct pwm_bl_data *pb; 202 int ret; 203 204 if (!data) { 205 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata); 206 if (ret < 0) { 207 dev_err(&pdev->dev, "failed to find platform data\n"); 208 return ret; 209 } 210 211 data = &defdata; 212 } 213 214 if (data->init) { 215 ret = data->init(&pdev->dev); 216 if (ret < 0) 217 return ret; 218 } 219 220 pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL); 221 if (!pb) { 222 ret = -ENOMEM; 223 goto err_alloc; 224 } 225 226 if (data->levels) { 227 unsigned int i; 228 229 for (i = 0; i <= data->max_brightness; i++) 230 if (data->levels[i] > pb->scale) 231 pb->scale = data->levels[i]; 232 233 pb->levels = data->levels; 234 } else 235 pb->scale = data->max_brightness; 236 237 pb->notify = data->notify; 238 pb->notify_after = data->notify_after; 239 pb->check_fb = data->check_fb; 240 pb->exit = data->exit; 241 pb->dev = &pdev->dev; 242 pb->enabled = false; 243 244 pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable"); 245 if (IS_ERR(pb->enable_gpio)) { 246 ret = PTR_ERR(pb->enable_gpio); 247 goto err_alloc; 248 } 249 250 /* 251 * Compatibility fallback for drivers still using the integer GPIO 252 * platform data. Must go away soon. 253 */ 254 if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) { 255 ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio, 256 GPIOF_OUT_INIT_HIGH, "enable"); 257 if (ret < 0) { 258 dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n", 259 data->enable_gpio, ret); 260 goto err_alloc; 261 } 262 263 pb->enable_gpio = gpio_to_desc(data->enable_gpio); 264 } 265 266 if (pb->enable_gpio) 267 gpiod_direction_output(pb->enable_gpio, 1); 268 269 pb->power_supply = devm_regulator_get(&pdev->dev, "power"); 270 if (IS_ERR(pb->power_supply)) { 271 ret = PTR_ERR(pb->power_supply); 272 goto err_alloc; 273 } 274 275 pb->pwm = devm_pwm_get(&pdev->dev, NULL); 276 if (IS_ERR(pb->pwm)) { 277 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n"); 278 pb->legacy = true; 279 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight"); 280 if (IS_ERR(pb->pwm)) { 281 dev_err(&pdev->dev, "unable to request legacy PWM\n"); 282 ret = PTR_ERR(pb->pwm); 283 goto err_alloc; 284 } 285 } 286 287 dev_dbg(&pdev->dev, "got pwm for backlight\n"); 288 289 /* 290 * The DT case will set the pwm_period_ns field to 0 and store the 291 * period, parsed from the DT, in the PWM device. For the non-DT case, 292 * set the period from platform data if it has not already been set 293 * via the PWM lookup table. 294 */ 295 pb->period = pwm_get_period(pb->pwm); 296 if (!pb->period && (data->pwm_period_ns > 0)) { 297 pb->period = data->pwm_period_ns; 298 pwm_set_period(pb->pwm, data->pwm_period_ns); 299 } 300 301 pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale); 302 303 memset(&props, 0, sizeof(struct backlight_properties)); 304 props.type = BACKLIGHT_RAW; 305 props.max_brightness = data->max_brightness; 306 bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb, 307 &pwm_backlight_ops, &props); 308 if (IS_ERR(bl)) { 309 dev_err(&pdev->dev, "failed to register backlight\n"); 310 ret = PTR_ERR(bl); 311 goto err_alloc; 312 } 313 314 if (data->dft_brightness > data->max_brightness) { 315 dev_warn(&pdev->dev, 316 "invalid default brightness level: %u, using %u\n", 317 data->dft_brightness, data->max_brightness); 318 data->dft_brightness = data->max_brightness; 319 } 320 321 bl->props.brightness = data->dft_brightness; 322 backlight_update_status(bl); 323 324 platform_set_drvdata(pdev, bl); 325 return 0; 326 327 err_alloc: 328 if (data->exit) 329 data->exit(&pdev->dev); 330 return ret; 331 } 332 333 static int pwm_backlight_remove(struct platform_device *pdev) 334 { 335 struct backlight_device *bl = platform_get_drvdata(pdev); 336 struct pwm_bl_data *pb = bl_get_data(bl); 337 338 backlight_device_unregister(bl); 339 pwm_backlight_power_off(pb); 340 341 if (pb->exit) 342 pb->exit(&pdev->dev); 343 if (pb->legacy) 344 pwm_free(pb->pwm); 345 346 return 0; 347 } 348 349 static void pwm_backlight_shutdown(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 pwm_backlight_power_off(pb); 355 } 356 357 #ifdef CONFIG_PM_SLEEP 358 static int pwm_backlight_suspend(struct device *dev) 359 { 360 struct backlight_device *bl = dev_get_drvdata(dev); 361 struct pwm_bl_data *pb = bl_get_data(bl); 362 363 if (pb->notify) 364 pb->notify(pb->dev, 0); 365 366 pwm_backlight_power_off(pb); 367 368 if (pb->notify_after) 369 pb->notify_after(pb->dev, 0); 370 371 return 0; 372 } 373 374 static int pwm_backlight_resume(struct device *dev) 375 { 376 struct backlight_device *bl = dev_get_drvdata(dev); 377 378 backlight_update_status(bl); 379 380 return 0; 381 } 382 #endif 383 384 static const struct dev_pm_ops pwm_backlight_pm_ops = { 385 #ifdef CONFIG_PM_SLEEP 386 .suspend = pwm_backlight_suspend, 387 .resume = pwm_backlight_resume, 388 .poweroff = pwm_backlight_suspend, 389 .restore = pwm_backlight_resume, 390 #endif 391 }; 392 393 static struct platform_driver pwm_backlight_driver = { 394 .driver = { 395 .name = "pwm-backlight", 396 .pm = &pwm_backlight_pm_ops, 397 .of_match_table = of_match_ptr(pwm_backlight_of_match), 398 }, 399 .probe = pwm_backlight_probe, 400 .remove = pwm_backlight_remove, 401 .shutdown = pwm_backlight_shutdown, 402 }; 403 404 module_platform_driver(pwm_backlight_driver); 405 406 MODULE_DESCRIPTION("PWM based Backlight Driver"); 407 MODULE_LICENSE("GPL"); 408 MODULE_ALIAS("platform:pwm-backlight"); 409