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 int (*notify)(struct device *, 38 int brightness); 39 void (*notify_after)(struct device *, 40 int brightness); 41 int (*check_fb)(struct device *, struct fb_info *); 42 void (*exit)(struct device *); 43 }; 44 45 static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness) 46 { 47 int err; 48 49 if (pb->enabled) 50 return; 51 52 err = regulator_enable(pb->power_supply); 53 if (err < 0) 54 dev_err(pb->dev, "failed to enable power supply\n"); 55 56 if (pb->enable_gpio) 57 gpiod_set_value(pb->enable_gpio, 1); 58 59 pwm_enable(pb->pwm); 60 pb->enabled = true; 61 } 62 63 static void pwm_backlight_power_off(struct pwm_bl_data *pb) 64 { 65 if (!pb->enabled) 66 return; 67 68 pwm_config(pb->pwm, 0, pb->period); 69 pwm_disable(pb->pwm); 70 71 if (pb->enable_gpio) 72 gpiod_set_value(pb->enable_gpio, 0); 73 74 regulator_disable(pb->power_supply); 75 pb->enabled = false; 76 } 77 78 static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness) 79 { 80 unsigned int lth = pb->lth_brightness; 81 int duty_cycle; 82 83 if (pb->levels) 84 duty_cycle = pb->levels[brightness]; 85 else 86 duty_cycle = brightness; 87 88 return (duty_cycle * (pb->period - lth) / pb->scale) + lth; 89 } 90 91 static int pwm_backlight_update_status(struct backlight_device *bl) 92 { 93 struct pwm_bl_data *pb = bl_get_data(bl); 94 int brightness = bl->props.brightness; 95 int duty_cycle; 96 97 if (bl->props.power != FB_BLANK_UNBLANK || 98 bl->props.fb_blank != FB_BLANK_UNBLANK || 99 bl->props.state & BL_CORE_FBBLANK) 100 brightness = 0; 101 102 if (pb->notify) 103 brightness = pb->notify(pb->dev, brightness); 104 105 if (brightness > 0) { 106 duty_cycle = compute_duty_cycle(pb, brightness); 107 pwm_config(pb->pwm, duty_cycle, pb->period); 108 pwm_backlight_power_on(pb, brightness); 109 } else 110 pwm_backlight_power_off(pb); 111 112 if (pb->notify_after) 113 pb->notify_after(pb->dev, brightness); 114 115 return 0; 116 } 117 118 static int pwm_backlight_check_fb(struct backlight_device *bl, 119 struct fb_info *info) 120 { 121 struct pwm_bl_data *pb = bl_get_data(bl); 122 123 return !pb->check_fb || pb->check_fb(pb->dev, info); 124 } 125 126 static const struct backlight_ops pwm_backlight_ops = { 127 .update_status = pwm_backlight_update_status, 128 .check_fb = pwm_backlight_check_fb, 129 }; 130 131 #ifdef CONFIG_OF 132 static int pwm_backlight_parse_dt(struct device *dev, 133 struct platform_pwm_backlight_data *data) 134 { 135 struct device_node *node = dev->of_node; 136 struct property *prop; 137 int length; 138 u32 value; 139 int ret; 140 141 if (!node) 142 return -ENODEV; 143 144 memset(data, 0, sizeof(*data)); 145 146 /* determine the number of brightness levels */ 147 prop = of_find_property(node, "brightness-levels", &length); 148 if (!prop) 149 return -EINVAL; 150 151 data->max_brightness = length / sizeof(u32); 152 153 /* read brightness levels from DT property */ 154 if (data->max_brightness > 0) { 155 size_t size = sizeof(*data->levels) * data->max_brightness; 156 157 data->levels = devm_kzalloc(dev, size, GFP_KERNEL); 158 if (!data->levels) 159 return -ENOMEM; 160 161 ret = of_property_read_u32_array(node, "brightness-levels", 162 data->levels, 163 data->max_brightness); 164 if (ret < 0) 165 return ret; 166 167 ret = of_property_read_u32(node, "default-brightness-level", 168 &value); 169 if (ret < 0) 170 return ret; 171 172 data->dft_brightness = value; 173 data->max_brightness--; 174 } 175 176 data->enable_gpio = -EINVAL; 177 return 0; 178 } 179 180 static struct of_device_id pwm_backlight_of_match[] = { 181 { .compatible = "pwm-backlight" }, 182 { } 183 }; 184 185 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match); 186 #else 187 static int pwm_backlight_parse_dt(struct device *dev, 188 struct platform_pwm_backlight_data *data) 189 { 190 return -ENODEV; 191 } 192 #endif 193 194 static int pwm_backlight_probe(struct platform_device *pdev) 195 { 196 struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev); 197 struct platform_pwm_backlight_data defdata; 198 struct backlight_properties props; 199 struct backlight_device *bl; 200 struct pwm_bl_data *pb; 201 int ret; 202 203 if (!data) { 204 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata); 205 if (ret < 0) { 206 dev_err(&pdev->dev, "failed to find platform data\n"); 207 return ret; 208 } 209 210 data = &defdata; 211 } 212 213 if (data->init) { 214 ret = data->init(&pdev->dev); 215 if (ret < 0) 216 return ret; 217 } 218 219 pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL); 220 if (!pb) { 221 ret = -ENOMEM; 222 goto err_alloc; 223 } 224 225 if (data->levels) { 226 unsigned int i; 227 228 for (i = 0; i <= data->max_brightness; i++) 229 if (data->levels[i] > pb->scale) 230 pb->scale = data->levels[i]; 231 232 pb->levels = data->levels; 233 } else 234 pb->scale = data->max_brightness; 235 236 pb->notify = data->notify; 237 pb->notify_after = data->notify_after; 238 pb->check_fb = data->check_fb; 239 pb->exit = data->exit; 240 pb->dev = &pdev->dev; 241 pb->enabled = false; 242 243 pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable"); 244 if (IS_ERR(pb->enable_gpio)) { 245 ret = PTR_ERR(pb->enable_gpio); 246 goto err_alloc; 247 } 248 249 /* 250 * Compatibility fallback for drivers still using the integer GPIO 251 * platform data. Must go away soon. 252 */ 253 if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) { 254 ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio, 255 GPIOF_OUT_INIT_HIGH, "enable"); 256 if (ret < 0) { 257 dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n", 258 data->enable_gpio, ret); 259 goto err_alloc; 260 } 261 262 pb->enable_gpio = gpio_to_desc(data->enable_gpio); 263 } 264 265 if (pb->enable_gpio) 266 gpiod_direction_output(pb->enable_gpio, 1); 267 268 pb->power_supply = devm_regulator_get(&pdev->dev, "power"); 269 if (IS_ERR(pb->power_supply)) { 270 ret = PTR_ERR(pb->power_supply); 271 goto err_alloc; 272 } 273 274 pb->pwm = devm_pwm_get(&pdev->dev, NULL); 275 if (IS_ERR(pb->pwm)) { 276 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n"); 277 278 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight"); 279 if (IS_ERR(pb->pwm)) { 280 dev_err(&pdev->dev, "unable to request legacy PWM\n"); 281 ret = PTR_ERR(pb->pwm); 282 goto err_alloc; 283 } 284 } 285 286 dev_dbg(&pdev->dev, "got pwm for backlight\n"); 287 288 /* 289 * The DT case will set the pwm_period_ns field to 0 and store the 290 * period, parsed from the DT, in the PWM device. For the non-DT case, 291 * set the period from platform data if it has not already been set 292 * via the PWM lookup table. 293 */ 294 pb->period = pwm_get_period(pb->pwm); 295 if (!pb->period && (data->pwm_period_ns > 0)) { 296 pb->period = data->pwm_period_ns; 297 pwm_set_period(pb->pwm, data->pwm_period_ns); 298 } 299 300 pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale); 301 302 memset(&props, 0, sizeof(struct backlight_properties)); 303 props.type = BACKLIGHT_RAW; 304 props.max_brightness = data->max_brightness; 305 bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb, 306 &pwm_backlight_ops, &props); 307 if (IS_ERR(bl)) { 308 dev_err(&pdev->dev, "failed to register backlight\n"); 309 ret = PTR_ERR(bl); 310 goto err_alloc; 311 } 312 313 if (data->dft_brightness > data->max_brightness) { 314 dev_warn(&pdev->dev, 315 "invalid default brightness level: %u, using %u\n", 316 data->dft_brightness, data->max_brightness); 317 data->dft_brightness = data->max_brightness; 318 } 319 320 bl->props.brightness = data->dft_brightness; 321 backlight_update_status(bl); 322 323 platform_set_drvdata(pdev, bl); 324 return 0; 325 326 err_alloc: 327 if (data->exit) 328 data->exit(&pdev->dev); 329 return ret; 330 } 331 332 static int pwm_backlight_remove(struct platform_device *pdev) 333 { 334 struct backlight_device *bl = platform_get_drvdata(pdev); 335 struct pwm_bl_data *pb = bl_get_data(bl); 336 337 backlight_device_unregister(bl); 338 pwm_backlight_power_off(pb); 339 340 if (pb->exit) 341 pb->exit(&pdev->dev); 342 343 return 0; 344 } 345 346 static void pwm_backlight_shutdown(struct platform_device *pdev) 347 { 348 struct backlight_device *bl = platform_get_drvdata(pdev); 349 struct pwm_bl_data *pb = bl_get_data(bl); 350 351 pwm_backlight_power_off(pb); 352 } 353 354 #ifdef CONFIG_PM_SLEEP 355 static int pwm_backlight_suspend(struct device *dev) 356 { 357 struct backlight_device *bl = dev_get_drvdata(dev); 358 struct pwm_bl_data *pb = bl_get_data(bl); 359 360 if (pb->notify) 361 pb->notify(pb->dev, 0); 362 363 pwm_backlight_power_off(pb); 364 365 if (pb->notify_after) 366 pb->notify_after(pb->dev, 0); 367 368 return 0; 369 } 370 371 static int pwm_backlight_resume(struct device *dev) 372 { 373 struct backlight_device *bl = dev_get_drvdata(dev); 374 375 backlight_update_status(bl); 376 377 return 0; 378 } 379 #endif 380 381 static const struct dev_pm_ops pwm_backlight_pm_ops = { 382 #ifdef CONFIG_PM_SLEEP 383 .suspend = pwm_backlight_suspend, 384 .resume = pwm_backlight_resume, 385 .poweroff = pwm_backlight_suspend, 386 .restore = pwm_backlight_resume, 387 #endif 388 }; 389 390 static struct platform_driver pwm_backlight_driver = { 391 .driver = { 392 .name = "pwm-backlight", 393 .pm = &pwm_backlight_pm_ops, 394 .of_match_table = of_match_ptr(pwm_backlight_of_match), 395 }, 396 .probe = pwm_backlight_probe, 397 .remove = pwm_backlight_remove, 398 .shutdown = pwm_backlight_shutdown, 399 }; 400 401 module_platform_driver(pwm_backlight_driver); 402 403 MODULE_DESCRIPTION("PWM based Backlight Driver"); 404 MODULE_LICENSE("GPL"); 405 MODULE_ALIAS("platform:pwm-backlight"); 406