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8#include <linux/delay.h>
9#include <linux/gpio/consumer.h>
10#include <linux/module.h>
11#include <linux/kernel.h>
12#include <linux/init.h>
13#include <linux/platform_device.h>
14#include <linux/fb.h>
15#include <linux/backlight.h>
16#include <linux/err.h>
17#include <linux/pwm.h>
18#include <linux/pwm_backlight.h>
19#include <linux/regulator/consumer.h>
20#include <linux/slab.h>
21
22struct pwm_bl_data {
23 struct pwm_device *pwm;
24 struct device *dev;
25 unsigned int lth_brightness;
26 unsigned int *levels;
27 bool enabled;
28 struct regulator *power_supply;
29 struct gpio_desc *enable_gpio;
30 unsigned int scale;
31 bool legacy;
32 unsigned int post_pwm_on_delay;
33 unsigned int pwm_off_delay;
34 int (*notify)(struct device *,
35 int brightness);
36 void (*notify_after)(struct device *,
37 int brightness);
38 int (*check_fb)(struct device *, struct fb_info *);
39 void (*exit)(struct device *);
40};
41
42static void pwm_backlight_power_on(struct pwm_bl_data *pb)
43{
44 struct pwm_state state;
45 int err;
46
47 pwm_get_state(pb->pwm, &state);
48 if (pb->enabled)
49 return;
50
51 err = regulator_enable(pb->power_supply);
52 if (err < 0)
53 dev_err(pb->dev, "failed to enable power supply\n");
54
55 state.enabled = true;
56 pwm_apply_state(pb->pwm, &state);
57
58 if (pb->post_pwm_on_delay)
59 msleep(pb->post_pwm_on_delay);
60
61 if (pb->enable_gpio)
62 gpiod_set_value_cansleep(pb->enable_gpio, 1);
63
64 pb->enabled = true;
65}
66
67static void pwm_backlight_power_off(struct pwm_bl_data *pb)
68{
69 struct pwm_state state;
70
71 pwm_get_state(pb->pwm, &state);
72 if (!pb->enabled)
73 return;
74
75 if (pb->enable_gpio)
76 gpiod_set_value_cansleep(pb->enable_gpio, 0);
77
78 if (pb->pwm_off_delay)
79 msleep(pb->pwm_off_delay);
80
81 state.enabled = false;
82 state.duty_cycle = 0;
83 pwm_apply_state(pb->pwm, &state);
84
85 regulator_disable(pb->power_supply);
86 pb->enabled = false;
87}
88
89static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
90{
91 unsigned int lth = pb->lth_brightness;
92 struct pwm_state state;
93 u64 duty_cycle;
94
95 pwm_get_state(pb->pwm, &state);
96
97 if (pb->levels)
98 duty_cycle = pb->levels[brightness];
99 else
100 duty_cycle = brightness;
101
102 duty_cycle *= state.period - lth;
103 do_div(duty_cycle, pb->scale);
104
105 return duty_cycle + lth;
106}
107
108static int pwm_backlight_update_status(struct backlight_device *bl)
109{
110 struct pwm_bl_data *pb = bl_get_data(bl);
111 int brightness = backlight_get_brightness(bl);
112 struct pwm_state state;
113
114 if (pb->notify)
115 brightness = pb->notify(pb->dev, brightness);
116
117 if (brightness > 0) {
118 pwm_get_state(pb->pwm, &state);
119 state.duty_cycle = compute_duty_cycle(pb, brightness);
120 pwm_apply_state(pb->pwm, &state);
121 pwm_backlight_power_on(pb);
122 } else {
123 pwm_backlight_power_off(pb);
124 }
125
126 if (pb->notify_after)
127 pb->notify_after(pb->dev, brightness);
128
129 return 0;
130}
131
132static 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
140static const struct backlight_ops pwm_backlight_ops = {
141 .update_status = pwm_backlight_update_status,
142 .check_fb = pwm_backlight_check_fb,
143};
144
145#ifdef CONFIG_OF
146#define PWM_LUMINANCE_SHIFT 16
147#define PWM_LUMINANCE_SCALE (1 << PWM_LUMINANCE_SHIFT)
148
149
150
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159
160
161
162
163
164static u64 cie1931(unsigned int lightness)
165{
166 u64 retval;
167
168
169
170
171
172
173
174
175 lightness *= 100;
176 if (lightness <= (8 * PWM_LUMINANCE_SCALE)) {
177 retval = DIV_ROUND_CLOSEST(lightness * 10, 9033);
178 } else {
179 retval = (lightness + (16 * PWM_LUMINANCE_SCALE)) / 116;
180 retval *= retval * retval;
181 retval += 1ULL << (2*PWM_LUMINANCE_SHIFT - 1);
182 retval >>= 2*PWM_LUMINANCE_SHIFT;
183 }
184
185 return retval;
186}
187
188
189
190
191
192static
193int pwm_backlight_brightness_default(struct device *dev,
194 struct platform_pwm_backlight_data *data,
195 unsigned int period)
196{
197 unsigned int i;
198 u64 retval;
199
200
201
202
203
204
205 data->max_brightness =
206 min((int)DIV_ROUND_UP(period, fls(period)), 4096);
207
208 data->levels = devm_kcalloc(dev, data->max_brightness,
209 sizeof(*data->levels), GFP_KERNEL);
210 if (!data->levels)
211 return -ENOMEM;
212
213
214 for (i = 0; i < data->max_brightness; i++) {
215 retval = cie1931((i * PWM_LUMINANCE_SCALE) /
216 data->max_brightness) * period;
217 retval = DIV_ROUND_CLOSEST_ULL(retval, PWM_LUMINANCE_SCALE);
218 if (retval > UINT_MAX)
219 return -EINVAL;
220 data->levels[i] = (unsigned int)retval;
221 }
222
223 data->dft_brightness = data->max_brightness / 2;
224 data->max_brightness--;
225
226 return 0;
227}
228
229static int pwm_backlight_parse_dt(struct device *dev,
230 struct platform_pwm_backlight_data *data)
231{
232 struct device_node *node = dev->of_node;
233 unsigned int num_levels;
234 unsigned int num_steps = 0;
235 struct property *prop;
236 unsigned int *table;
237 int length;
238 u32 value;
239 int ret;
240
241 if (!node)
242 return -ENODEV;
243
244 memset(data, 0, sizeof(*data));
245
246
247
248
249
250 of_property_read_u32(node, "post-pwm-on-delay-ms",
251 &data->post_pwm_on_delay);
252 of_property_read_u32(node, "pwm-off-delay-ms", &data->pwm_off_delay);
253
254
255
256
257
258 prop = of_find_property(node, "brightness-levels", &length);
259 if (!prop)
260 return 0;
261
262 num_levels = length / sizeof(u32);
263
264
265 if (num_levels > 0) {
266 size_t size = sizeof(*data->levels) * num_levels;
267
268 data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
269 if (!data->levels)
270 return -ENOMEM;
271
272 ret = of_property_read_u32_array(node, "brightness-levels",
273 data->levels,
274 num_levels);
275 if (ret < 0)
276 return ret;
277
278 ret = of_property_read_u32(node, "default-brightness-level",
279 &value);
280 if (ret < 0)
281 return ret;
282
283 data->dft_brightness = value;
284
285
286
287
288
289
290 of_property_read_u32(node, "num-interpolated-steps",
291 &num_steps);
292
293
294
295
296
297
298 if (num_steps) {
299 unsigned int num_input_levels = num_levels;
300 unsigned int i;
301 u32 x1, x2, x, dx;
302 u32 y1, y2;
303 s64 dy;
304
305 if (num_input_levels < 2) {
306 dev_err(dev, "can't interpolate\n");
307 return -EINVAL;
308 }
309
310
311
312
313
314
315 num_levels = (num_input_levels - 1) * num_steps + 1;
316 dev_dbg(dev, "new number of brightness levels: %d\n",
317 num_levels);
318
319
320
321
322
323 size = sizeof(*table) * num_levels;
324 table = devm_kzalloc(dev, size, GFP_KERNEL);
325 if (!table)
326 return -ENOMEM;
327
328
329
330
331 dx = num_steps;
332 for (i = 0; i < num_input_levels - 1; i++) {
333 x1 = i * dx;
334 x2 = x1 + dx;
335 y1 = data->levels[i];
336 y2 = data->levels[i + 1];
337 dy = (s64)y2 - y1;
338
339 for (x = x1; x < x2; x++) {
340 table[x] = y1 +
341 div_s64(dy * (x - x1), dx);
342 }
343 }
344
345 table[x2] = y2;
346
347
348
349
350
351
352 devm_kfree(dev, data->levels);
353 data->levels = table;
354 }
355
356 data->max_brightness = num_levels - 1;
357 }
358
359 return 0;
360}
361
362static const struct of_device_id pwm_backlight_of_match[] = {
363 { .compatible = "pwm-backlight" },
364 { }
365};
366
367MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
368#else
369static int pwm_backlight_parse_dt(struct device *dev,
370 struct platform_pwm_backlight_data *data)
371{
372 return -ENODEV;
373}
374
375static
376int pwm_backlight_brightness_default(struct device *dev,
377 struct platform_pwm_backlight_data *data,
378 unsigned int period)
379{
380 return -ENODEV;
381}
382#endif
383
384static bool pwm_backlight_is_linear(struct platform_pwm_backlight_data *data)
385{
386 unsigned int nlevels = data->max_brightness + 1;
387 unsigned int min_val = data->levels[0];
388 unsigned int max_val = data->levels[nlevels - 1];
389
390
391
392
393
394 unsigned int slope = (128 * (max_val - min_val)) / nlevels;
395 unsigned int margin = (max_val - min_val) / 20;
396 int i;
397
398 for (i = 1; i < nlevels; i++) {
399 unsigned int linear_value = min_val + ((i * slope) / 128);
400 unsigned int delta = abs(linear_value - data->levels[i]);
401
402 if (delta > margin)
403 return false;
404 }
405
406 return true;
407}
408
409static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
410{
411 struct device_node *node = pb->dev->of_node;
412 bool active = true;
413
414
415
416
417
418 if (pb->enable_gpio && gpiod_get_value_cansleep(pb->enable_gpio) == 0)
419 active = false;
420
421 if (!regulator_is_enabled(pb->power_supply))
422 active = false;
423
424 if (!pwm_is_enabled(pb->pwm))
425 active = false;
426
427
428
429
430
431 if (pb->enable_gpio)
432 gpiod_direction_output(pb->enable_gpio, active);
433
434
435
436
437
438
439
440
441 if (!node || !node->phandle)
442 return FB_BLANK_UNBLANK;
443
444
445
446
447
448
449
450 return active ? FB_BLANK_UNBLANK: FB_BLANK_POWERDOWN;
451}
452
453static int pwm_backlight_probe(struct platform_device *pdev)
454{
455 struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
456 struct platform_pwm_backlight_data defdata;
457 struct backlight_properties props;
458 struct backlight_device *bl;
459 struct device_node *node = pdev->dev.of_node;
460 struct pwm_bl_data *pb;
461 struct pwm_state state;
462 unsigned int i;
463 int ret;
464
465 if (!data) {
466 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
467 if (ret < 0) {
468 dev_err(&pdev->dev, "failed to find platform data\n");
469 return ret;
470 }
471
472 data = &defdata;
473 }
474
475 if (data->init) {
476 ret = data->init(&pdev->dev);
477 if (ret < 0)
478 return ret;
479 }
480
481 pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
482 if (!pb) {
483 ret = -ENOMEM;
484 goto err_alloc;
485 }
486
487 pb->notify = data->notify;
488 pb->notify_after = data->notify_after;
489 pb->check_fb = data->check_fb;
490 pb->exit = data->exit;
491 pb->dev = &pdev->dev;
492 pb->enabled = false;
493 pb->post_pwm_on_delay = data->post_pwm_on_delay;
494 pb->pwm_off_delay = data->pwm_off_delay;
495
496 pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
497 GPIOD_ASIS);
498 if (IS_ERR(pb->enable_gpio)) {
499 ret = PTR_ERR(pb->enable_gpio);
500 goto err_alloc;
501 }
502
503 pb->power_supply = devm_regulator_get(&pdev->dev, "power");
504 if (IS_ERR(pb->power_supply)) {
505 ret = PTR_ERR(pb->power_supply);
506 goto err_alloc;
507 }
508
509 pb->pwm = devm_pwm_get(&pdev->dev, NULL);
510 if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) {
511 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
512 pb->legacy = true;
513 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
514 }
515
516 if (IS_ERR(pb->pwm)) {
517 ret = PTR_ERR(pb->pwm);
518 if (ret != -EPROBE_DEFER)
519 dev_err(&pdev->dev, "unable to request PWM\n");
520 goto err_alloc;
521 }
522
523 dev_dbg(&pdev->dev, "got pwm for backlight\n");
524
525
526 pwm_init_state(pb->pwm, &state);
527
528
529
530
531
532
533
534 if (!state.period && (data->pwm_period_ns > 0))
535 state.period = data->pwm_period_ns;
536
537 ret = pwm_apply_state(pb->pwm, &state);
538 if (ret) {
539 dev_err(&pdev->dev, "failed to apply initial PWM state: %d\n",
540 ret);
541 goto err_alloc;
542 }
543
544 memset(&props, 0, sizeof(struct backlight_properties));
545
546 if (data->levels) {
547 pb->levels = data->levels;
548
549
550
551
552
553
554 for (i = 0; i <= data->max_brightness; i++)
555 if (data->levels[i] > pb->scale)
556 pb->scale = data->levels[i];
557
558 if (pwm_backlight_is_linear(data))
559 props.scale = BACKLIGHT_SCALE_LINEAR;
560 else
561 props.scale = BACKLIGHT_SCALE_NON_LINEAR;
562 } else if (!data->max_brightness) {
563
564
565
566
567
568
569
570
571
572 pwm_get_state(pb->pwm, &state);
573
574 ret = pwm_backlight_brightness_default(&pdev->dev, data,
575 state.period);
576 if (ret < 0) {
577 dev_err(&pdev->dev,
578 "failed to setup default brightness table\n");
579 goto err_alloc;
580 }
581
582 for (i = 0; i <= data->max_brightness; i++) {
583 if (data->levels[i] > pb->scale)
584 pb->scale = data->levels[i];
585
586 pb->levels = data->levels;
587 }
588
589 props.scale = BACKLIGHT_SCALE_NON_LINEAR;
590 } else {
591
592
593
594
595 pb->scale = data->max_brightness;
596 }
597
598 pb->lth_brightness = data->lth_brightness * (div_u64(state.period,
599 pb->scale));
600
601 props.type = BACKLIGHT_RAW;
602 props.max_brightness = data->max_brightness;
603 bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
604 &pwm_backlight_ops, &props);
605 if (IS_ERR(bl)) {
606 dev_err(&pdev->dev, "failed to register backlight\n");
607 ret = PTR_ERR(bl);
608 if (pb->legacy)
609 pwm_free(pb->pwm);
610 goto err_alloc;
611 }
612
613 if (data->dft_brightness > data->max_brightness) {
614 dev_warn(&pdev->dev,
615 "invalid default brightness level: %u, using %u\n",
616 data->dft_brightness, data->max_brightness);
617 data->dft_brightness = data->max_brightness;
618 }
619
620 bl->props.brightness = data->dft_brightness;
621 bl->props.power = pwm_backlight_initial_power_state(pb);
622 backlight_update_status(bl);
623
624 platform_set_drvdata(pdev, bl);
625 return 0;
626
627err_alloc:
628 if (data->exit)
629 data->exit(&pdev->dev);
630 return ret;
631}
632
633static int pwm_backlight_remove(struct platform_device *pdev)
634{
635 struct backlight_device *bl = platform_get_drvdata(pdev);
636 struct pwm_bl_data *pb = bl_get_data(bl);
637
638 backlight_device_unregister(bl);
639 pwm_backlight_power_off(pb);
640
641 if (pb->exit)
642 pb->exit(&pdev->dev);
643 if (pb->legacy)
644 pwm_free(pb->pwm);
645
646 return 0;
647}
648
649static void pwm_backlight_shutdown(struct platform_device *pdev)
650{
651 struct backlight_device *bl = platform_get_drvdata(pdev);
652 struct pwm_bl_data *pb = bl_get_data(bl);
653
654 pwm_backlight_power_off(pb);
655}
656
657#ifdef CONFIG_PM_SLEEP
658static int pwm_backlight_suspend(struct device *dev)
659{
660 struct backlight_device *bl = dev_get_drvdata(dev);
661 struct pwm_bl_data *pb = bl_get_data(bl);
662
663 if (pb->notify)
664 pb->notify(pb->dev, 0);
665
666 pwm_backlight_power_off(pb);
667
668 if (pb->notify_after)
669 pb->notify_after(pb->dev, 0);
670
671 return 0;
672}
673
674static int pwm_backlight_resume(struct device *dev)
675{
676 struct backlight_device *bl = dev_get_drvdata(dev);
677
678 backlight_update_status(bl);
679
680 return 0;
681}
682#endif
683
684static const struct dev_pm_ops pwm_backlight_pm_ops = {
685#ifdef CONFIG_PM_SLEEP
686 .suspend = pwm_backlight_suspend,
687 .resume = pwm_backlight_resume,
688 .poweroff = pwm_backlight_suspend,
689 .restore = pwm_backlight_resume,
690#endif
691};
692
693static struct platform_driver pwm_backlight_driver = {
694 .driver = {
695 .name = "pwm-backlight",
696 .pm = &pwm_backlight_pm_ops,
697 .of_match_table = of_match_ptr(pwm_backlight_of_match),
698 },
699 .probe = pwm_backlight_probe,
700 .remove = pwm_backlight_remove,
701 .shutdown = pwm_backlight_shutdown,
702};
703
704module_platform_driver(pwm_backlight_driver);
705
706MODULE_DESCRIPTION("PWM based Backlight Driver");
707MODULE_LICENSE("GPL v2");
708MODULE_ALIAS("platform:pwm-backlight");
709