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
pwm_backlight_power_on(struct pwm_bl_data * pb,int brightness)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
pwm_backlight_power_off(struct pwm_bl_data * pb)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
compute_duty_cycle(struct pwm_bl_data * pb,int brightness)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
pwm_backlight_update_status(struct backlight_device * bl)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
pwm_backlight_check_fb(struct backlight_device * bl,struct fb_info * info)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
pwm_backlight_parse_dt(struct device * dev,struct platform_pwm_backlight_data * data)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
pwm_backlight_parse_dt(struct device * dev,struct platform_pwm_backlight_data * data)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
pwm_backlight_probe(struct platform_device * pdev)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 GPIOD_OUT_HIGH);
246 if (IS_ERR(pb->enable_gpio)) {
247 ret = PTR_ERR(pb->enable_gpio);
248 goto err_alloc;
249 }
250
251 /*
252 * Compatibility fallback for drivers still using the integer GPIO
253 * platform data. Must go away soon.
254 */
255 if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
256 ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
257 GPIOF_OUT_INIT_HIGH, "enable");
258 if (ret < 0) {
259 dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
260 data->enable_gpio, ret);
261 goto err_alloc;
262 }
263
264 pb->enable_gpio = gpio_to_desc(data->enable_gpio);
265 }
266
267 pb->power_supply = devm_regulator_get(&pdev->dev, "power");
268 if (IS_ERR(pb->power_supply)) {
269 ret = PTR_ERR(pb->power_supply);
270 goto err_alloc;
271 }
272
273 pb->pwm = devm_pwm_get(&pdev->dev, NULL);
274 if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER
275 && !pdev->dev.of_node) {
276 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
277 pb->legacy = true;
278 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
279 }
280
281 if (IS_ERR(pb->pwm)) {
282 ret = PTR_ERR(pb->pwm);
283 if (ret != -EPROBE_DEFER)
284 dev_err(&pdev->dev, "unable to request PWM\n");
285 goto err_alloc;
286 }
287
288 dev_dbg(&pdev->dev, "got pwm for backlight\n");
289
290 /*
291 * The DT case will set the pwm_period_ns field to 0 and store the
292 * period, parsed from the DT, in the PWM device. For the non-DT case,
293 * set the period from platform data if it has not already been set
294 * via the PWM lookup table.
295 */
296 pb->period = pwm_get_period(pb->pwm);
297 if (!pb->period && (data->pwm_period_ns > 0)) {
298 pb->period = data->pwm_period_ns;
299 pwm_set_period(pb->pwm, data->pwm_period_ns);
300 }
301
302 pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
303
304 memset(&props, 0, sizeof(struct backlight_properties));
305 props.type = BACKLIGHT_RAW;
306 props.max_brightness = data->max_brightness;
307 bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
308 &pwm_backlight_ops, &props);
309 if (IS_ERR(bl)) {
310 dev_err(&pdev->dev, "failed to register backlight\n");
311 ret = PTR_ERR(bl);
312 goto err_alloc;
313 }
314
315 if (data->dft_brightness > data->max_brightness) {
316 dev_warn(&pdev->dev,
317 "invalid default brightness level: %u, using %u\n",
318 data->dft_brightness, data->max_brightness);
319 data->dft_brightness = data->max_brightness;
320 }
321
322 bl->props.brightness = data->dft_brightness;
323 backlight_update_status(bl);
324
325 platform_set_drvdata(pdev, bl);
326 return 0;
327
328 err_alloc:
329 if (data->exit)
330 data->exit(&pdev->dev);
331 return ret;
332 }
333
pwm_backlight_remove(struct platform_device * pdev)334 static int pwm_backlight_remove(struct platform_device *pdev)
335 {
336 struct backlight_device *bl = platform_get_drvdata(pdev);
337 struct pwm_bl_data *pb = bl_get_data(bl);
338
339 backlight_device_unregister(bl);
340 pwm_backlight_power_off(pb);
341
342 if (pb->exit)
343 pb->exit(&pdev->dev);
344 if (pb->legacy)
345 pwm_free(pb->pwm);
346
347 return 0;
348 }
349
pwm_backlight_shutdown(struct platform_device * pdev)350 static void pwm_backlight_shutdown(struct platform_device *pdev)
351 {
352 struct backlight_device *bl = platform_get_drvdata(pdev);
353 struct pwm_bl_data *pb = bl_get_data(bl);
354
355 pwm_backlight_power_off(pb);
356 }
357
358 #ifdef CONFIG_PM_SLEEP
pwm_backlight_suspend(struct device * dev)359 static int pwm_backlight_suspend(struct device *dev)
360 {
361 struct backlight_device *bl = dev_get_drvdata(dev);
362 struct pwm_bl_data *pb = bl_get_data(bl);
363
364 if (pb->notify)
365 pb->notify(pb->dev, 0);
366
367 pwm_backlight_power_off(pb);
368
369 if (pb->notify_after)
370 pb->notify_after(pb->dev, 0);
371
372 return 0;
373 }
374
pwm_backlight_resume(struct device * dev)375 static int pwm_backlight_resume(struct device *dev)
376 {
377 struct backlight_device *bl = dev_get_drvdata(dev);
378
379 backlight_update_status(bl);
380
381 return 0;
382 }
383 #endif
384
385 static const struct dev_pm_ops pwm_backlight_pm_ops = {
386 #ifdef CONFIG_PM_SLEEP
387 .suspend = pwm_backlight_suspend,
388 .resume = pwm_backlight_resume,
389 .poweroff = pwm_backlight_suspend,
390 .restore = pwm_backlight_resume,
391 #endif
392 };
393
394 static struct platform_driver pwm_backlight_driver = {
395 .driver = {
396 .name = "pwm-backlight",
397 .pm = &pwm_backlight_pm_ops,
398 .of_match_table = of_match_ptr(pwm_backlight_of_match),
399 },
400 .probe = pwm_backlight_probe,
401 .remove = pwm_backlight_remove,
402 .shutdown = pwm_backlight_shutdown,
403 };
404
405 module_platform_driver(pwm_backlight_driver);
406
407 MODULE_DESCRIPTION("PWM based Backlight Driver");
408 MODULE_LICENSE("GPL");
409 MODULE_ALIAS("platform:pwm-backlight");
410