| 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 device_node *node = pdev->dev.of_node; |
| 202 | struct pwm_bl_data *pb; |
| 203 | int initial_blank = FB_BLANK_UNBLANK; |
| 204 | struct pwm_args pargs; |
| 205 | int ret; |
| 206 | |
| 207 | if (!data) { |
| 208 | ret = pwm_backlight_parse_dt(&pdev->dev, &defdata); |
| 209 | if (ret < 0) { |
| 210 | dev_err(&pdev->dev, "failed to find platform data\n"); |
| 211 | return ret; |
| 212 | } |
| 213 | |
| 214 | data = &defdata; |
| 215 | } |
| 216 | |
| 217 | if (data->init) { |
| 218 | ret = data->init(&pdev->dev); |
| 219 | if (ret < 0) |
| 220 | return ret; |
| 221 | } |
| 222 | |
| 223 | pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL); |
| 224 | if (!pb) { |
| 225 | ret = -ENOMEM; |
| 226 | goto err_alloc; |
| 227 | } |
| 228 | |
| 229 | if (data->levels) { |
| 230 | unsigned int i; |
| 231 | |
| 232 | for (i = 0; i <= data->max_brightness; i++) |
| 233 | if (data->levels[i] > pb->scale) |
| 234 | pb->scale = data->levels[i]; |
| 235 | |
| 236 | pb->levels = data->levels; |
| 237 | } else |
| 238 | pb->scale = data->max_brightness; |
| 239 | |
| 240 | pb->notify = data->notify; |
| 241 | pb->notify_after = data->notify_after; |
| 242 | pb->check_fb = data->check_fb; |
| 243 | pb->exit = data->exit; |
| 244 | pb->dev = &pdev->dev; |
| 245 | pb->enabled = false; |
| 246 | |
| 247 | pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable", |
| 248 | GPIOD_ASIS); |
| 249 | if (IS_ERR(pb->enable_gpio)) { |
| 250 | ret = PTR_ERR(pb->enable_gpio); |
| 251 | goto err_alloc; |
| 252 | } |
| 253 | |
| 254 | /* |
| 255 | * Compatibility fallback for drivers still using the integer GPIO |
| 256 | * platform data. Must go away soon. |
| 257 | */ |
| 258 | if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) { |
| 259 | ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio, |
| 260 | GPIOF_OUT_INIT_HIGH, "enable"); |
| 261 | if (ret < 0) { |
| 262 | dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n", |
| 263 | data->enable_gpio, ret); |
| 264 | goto err_alloc; |
| 265 | } |
| 266 | |
| 267 | pb->enable_gpio = gpio_to_desc(data->enable_gpio); |
| 268 | } |
| 269 | |
| 270 | if (pb->enable_gpio) { |
| 271 | /* |
| 272 | * If the driver is probed from the device tree and there is a |
| 273 | * phandle link pointing to the backlight node, it is safe to |
| 274 | * assume that another driver will enable the backlight at the |
| 275 | * appropriate time. Therefore, if it is disabled, keep it so. |
| 276 | */ |
| 277 | if (node && node->phandle && |
| 278 | gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_OUT && |
| 279 | gpiod_get_value(pb->enable_gpio) == 0) |
| 280 | initial_blank = FB_BLANK_POWERDOWN; |
| 281 | else |
| 282 | gpiod_direction_output(pb->enable_gpio, 1); |
| 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_alloc; |
| 289 | } |
| 290 | |
| 291 | if (node && node->phandle && !regulator_is_enabled(pb->power_supply)) |
| 292 | initial_blank = FB_BLANK_POWERDOWN; |
| 293 | |
| 294 | pb->pwm = devm_pwm_get(&pdev->dev, NULL); |
| 295 | if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) { |
| 296 | dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n"); |
| 297 | pb->legacy = true; |
| 298 | pb->pwm = pwm_request(data->pwm_id, "pwm-backlight"); |
| 299 | } |
| 300 | |
| 301 | if (IS_ERR(pb->pwm)) { |
| 302 | ret = PTR_ERR(pb->pwm); |
| 303 | if (ret != -EPROBE_DEFER) |
| 304 | dev_err(&pdev->dev, "unable to request PWM\n"); |
| 305 | goto err_alloc; |
| 306 | } |
| 307 | |
| 308 | dev_dbg(&pdev->dev, "got pwm for backlight\n"); |
| 309 | |
| 310 | /* |
| 311 | * FIXME: pwm_apply_args() should be removed when switching to |
| 312 | * the atomic PWM API. |
| 313 | */ |
| 314 | pwm_apply_args(pb->pwm); |
| 315 | |
| 316 | /* |
| 317 | * The DT case will set the pwm_period_ns field to 0 and store the |
| 318 | * period, parsed from the DT, in the PWM device. For the non-DT case, |
| 319 | * set the period from platform data if it has not already been set |
| 320 | * via the PWM lookup table. |
| 321 | */ |
| 322 | pwm_get_args(pb->pwm, &pargs); |
| 323 | pb->period = pargs.period; |
| 324 | if (!pb->period && (data->pwm_period_ns > 0)) |
| 325 | pb->period = data->pwm_period_ns; |
| 326 | |
| 327 | pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale); |
| 328 | |
| 329 | memset(&props, 0, sizeof(struct backlight_properties)); |
| 330 | props.type = BACKLIGHT_RAW; |
| 331 | props.max_brightness = data->max_brightness; |
| 332 | bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb, |
| 333 | &pwm_backlight_ops, &props); |
| 334 | if (IS_ERR(bl)) { |
| 335 | dev_err(&pdev->dev, "failed to register backlight\n"); |
| 336 | ret = PTR_ERR(bl); |
| 337 | if (pb->legacy) |
| 338 | pwm_free(pb->pwm); |
| 339 | goto err_alloc; |
| 340 | } |
| 341 | |
| 342 | if (data->dft_brightness > data->max_brightness) { |
| 343 | dev_warn(&pdev->dev, |
| 344 | "invalid default brightness level: %u, using %u\n", |
| 345 | data->dft_brightness, data->max_brightness); |
| 346 | data->dft_brightness = data->max_brightness; |
| 347 | } |
| 348 | |
| 349 | bl->props.brightness = data->dft_brightness; |
| 350 | bl->props.power = initial_blank; |
| 351 | backlight_update_status(bl); |
| 352 | |
| 353 | platform_set_drvdata(pdev, bl); |
| 354 | return 0; |
| 355 | |
| 356 | err_alloc: |
| 357 | if (data->exit) |
| 358 | data->exit(&pdev->dev); |
| 359 | return ret; |
| 360 | } |
| 361 | |
| 362 | static int pwm_backlight_remove(struct platform_device *pdev) |
| 363 | { |
| 364 | struct backlight_device *bl = platform_get_drvdata(pdev); |
| 365 | struct pwm_bl_data *pb = bl_get_data(bl); |
| 366 | |
| 367 | backlight_device_unregister(bl); |
| 368 | pwm_backlight_power_off(pb); |
| 369 | |
| 370 | if (pb->exit) |
| 371 | pb->exit(&pdev->dev); |
| 372 | if (pb->legacy) |
| 373 | pwm_free(pb->pwm); |
| 374 | |
| 375 | return 0; |
| 376 | } |
| 377 | |
| 378 | static void pwm_backlight_shutdown(struct platform_device *pdev) |
| 379 | { |
| 380 | struct backlight_device *bl = platform_get_drvdata(pdev); |
| 381 | struct pwm_bl_data *pb = bl_get_data(bl); |
| 382 | |
| 383 | pwm_backlight_power_off(pb); |
| 384 | } |
| 385 | |
| 386 | #ifdef CONFIG_PM_SLEEP |
| 387 | static int pwm_backlight_suspend(struct device *dev) |
| 388 | { |
| 389 | struct backlight_device *bl = dev_get_drvdata(dev); |
| 390 | struct pwm_bl_data *pb = bl_get_data(bl); |
| 391 | |
| 392 | if (pb->notify) |
| 393 | pb->notify(pb->dev, 0); |
| 394 | |
| 395 | pwm_backlight_power_off(pb); |
| 396 | |
| 397 | if (pb->notify_after) |
| 398 | pb->notify_after(pb->dev, 0); |
| 399 | |
| 400 | return 0; |
| 401 | } |
| 402 | |
| 403 | static int pwm_backlight_resume(struct device *dev) |
| 404 | { |
| 405 | struct backlight_device *bl = dev_get_drvdata(dev); |
| 406 | |
| 407 | backlight_update_status(bl); |
| 408 | |
| 409 | return 0; |
| 410 | } |
| 411 | #endif |
| 412 | |
| 413 | static const struct dev_pm_ops pwm_backlight_pm_ops = { |
| 414 | #ifdef CONFIG_PM_SLEEP |
| 415 | .suspend = pwm_backlight_suspend, |
| 416 | .resume = pwm_backlight_resume, |
| 417 | .poweroff = pwm_backlight_suspend, |
| 418 | .restore = pwm_backlight_resume, |
| 419 | #endif |
| 420 | }; |
| 421 | |
| 422 | static struct platform_driver pwm_backlight_driver = { |
| 423 | .driver = { |
| 424 | .name = "pwm-backlight", |
| 425 | .pm = &pwm_backlight_pm_ops, |
| 426 | .of_match_table = of_match_ptr(pwm_backlight_of_match), |
| 427 | }, |
| 428 | .probe = pwm_backlight_probe, |
| 429 | .remove = pwm_backlight_remove, |
| 430 | .shutdown = pwm_backlight_shutdown, |
| 431 | }; |
| 432 | |
| 433 | module_platform_driver(pwm_backlight_driver); |
| 434 | |
| 435 | MODULE_DESCRIPTION("PWM based Backlight Driver"); |
| 436 | MODULE_LICENSE("GPL"); |
| 437 | MODULE_ALIAS("platform:pwm-backlight"); |