Release 4.11 drivers/video/backlight/pwm_bl.c

/*
 * linux/drivers/video/backlight/pwm_bl.c
 *
 * simple PWM based backlight control, board code has to setup
 * 1) pin configuration so PWM waveforms can output
 * 2) platform_data being correctly configured
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/gpio/consumer.h>
#include <linux/gpio.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/fb.h>
#include <linux/backlight.h>
#include <linux/err.h>
#include <linux/pwm.h>
#include <linux/pwm_backlight.h>
#include <linux/regulator/consumer.h>
#include <linux/slab.h>


struct pwm_bl_data {
	
struct pwm_device	*pwm;
	
struct device		*dev;
	
unsigned int		period;
	
unsigned int		lth_brightness;
	
unsigned int		*levels;
	
bool			enabled;
	
struct regulator	*power_supply;
	
struct gpio_desc	*enable_gpio;
	
unsigned int		scale;
	
bool			legacy;
	
int			(*notify)(struct device *,
					  int brightness);
	
void			(*notify_after)(struct device *,
					int brightness);
	
int			(*check_fb)(struct device *, struct fb_info *);
	
void			(*exit)(struct device *);
};



static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
{
	int err;

	if (pb->enabled)
		return;

	err = regulator_enable(pb->power_supply);
	if (err < 0)
		dev_err(pb->dev, "failed to enable power supply\n");

	if (pb->enable_gpio)
		gpiod_set_value_cansleep(pb->enable_gpio, 1);

	pwm_enable(pb->pwm);
	pb->enabled = true;
}

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static void pwm_backlight_power_off(struct pwm_bl_data *pb)
{
	if (!pb->enabled)
		return;

	pwm_config(pb->pwm, 0, pb->period);
	pwm_disable(pb->pwm);

	if (pb->enable_gpio)
		gpiod_set_value_cansleep(pb->enable_gpio, 0);

	regulator_disable(pb->power_supply);
	pb->enabled = false;
}

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static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
{
	unsigned int lth = pb->lth_brightness;
	int duty_cycle;

	if (pb->levels)
		duty_cycle = pb->levels[brightness];
	else
		duty_cycle = brightness;

	return (duty_cycle * (pb->period - lth) / pb->scale) + lth;
}

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static int pwm_backlight_update_status(struct backlight_device *bl)
{
	struct pwm_bl_data *pb = bl_get_data(bl);
	int brightness = bl->props.brightness;
	int duty_cycle;

	if (bl->props.power != FB_BLANK_UNBLANK ||
	    bl->props.fb_blank != FB_BLANK_UNBLANK ||
	    bl->props.state & BL_CORE_FBBLANK)
		brightness = 0;

	if (pb->notify)
		brightness = pb->notify(pb->dev, brightness);

	if (brightness > 0) {
		duty_cycle = compute_duty_cycle(pb, brightness);
		pwm_config(pb->pwm, duty_cycle, pb->period);
		pwm_backlight_power_on(pb, brightness);
	} else
		pwm_backlight_power_off(pb);

	if (pb->notify_after)
		pb->notify_after(pb->dev, brightness);

	return 0;
}

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Philipp Zabel
15
10.34%
1
9.09%
Thierry Reding
12
8.28%
3
27.27%
Alexandre Courbot
11
7.59%
2
18.18%
Arun Murthy
9
6.21%
1
9.09%
Ben Dooks
4
2.76%
1
9.09%
Jingoo Han
1
0.69%
1
9.09%
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145
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11
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static int pwm_backlight_check_fb(struct backlight_device *bl,
				  struct fb_info *info)
{
	struct pwm_bl_data *pb = bl_get_data(bl);

	return !pb->check_fb || pb->check_fb(pb->dev, info);
}

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static const struct backlight_ops pwm_backlight_ops = {
	.update_status	= pwm_backlight_update_status,
	.check_fb	= pwm_backlight_check_fb,
};

#ifdef CONFIG_OF


static int pwm_backlight_parse_dt(struct device *dev,
				  struct platform_pwm_backlight_data *data)
{
	struct device_node *node = dev->of_node;
	struct property *prop;
	int length;
	u32 value;
	int ret;

	if (!node)
		return -ENODEV;

	memset(data, 0, sizeof(*data));

	/* determine the number of brightness levels */
	prop = of_find_property(node, "brightness-levels", &length);
	if (!prop)
		return -EINVAL;

	data->max_brightness = length / sizeof(u32);

	/* read brightness levels from DT property */
	if (data->max_brightness > 0) {
		size_t size = sizeof(*data->levels) * data->max_brightness;

		data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
		if (!data->levels)
			return -ENOMEM;

		ret = of_property_read_u32_array(node, "brightness-levels",
						 data->levels,
						 data->max_brightness);
		if (ret < 0)
			return ret;

		ret = of_property_read_u32(node, "default-brightness-level",
					   &value);
		if (ret < 0)
			return ret;

		data->dft_brightness = value;
		data->max_brightness--;
	}

	data->enable_gpio = -EINVAL;
	return 0;
}

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static struct of_device_id pwm_backlight_of_match[] = {
	{ .compatible = "pwm-backlight" },
	{ }
};

MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
#else


static int pwm_backlight_parse_dt(struct device *dev,
				  struct platform_pwm_backlight_data *data)
{
	return -ENODEV;
}
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#endif



static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
{
	struct device_node *node = pb->dev->of_node;

	/* Not booted with device tree or no phandle link to the node */
	if (!node || !node->phandle)
		return FB_BLANK_UNBLANK;

	/*
         * If the driver is probed from the device tree and there is a
         * phandle link pointing to the backlight node, it is safe to
         * assume that another driver will enable the backlight at the
         * appropriate time. Therefore, if it is disabled, keep it so.
         */

	/* if the enable GPIO is disabled, do not enable the backlight */
	if (pb->enable_gpio && gpiod_get_value(pb->enable_gpio) == 0)
		return FB_BLANK_POWERDOWN;

	/* The regulator is disabled, do not enable the backlight */
	if (!regulator_is_enabled(pb->power_supply))
		return FB_BLANK_POWERDOWN;

	/* The PWM is disabled, keep it like this */
	if (!pwm_is_enabled(pb->pwm))
		return FB_BLANK_POWERDOWN;

	return FB_BLANK_UNBLANK;
}

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static int pwm_backlight_probe(struct platform_device *pdev)
{
	struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
	struct platform_pwm_backlight_data defdata;
	struct backlight_properties props;
	struct backlight_device *bl;
	struct device_node *node = pdev->dev.of_node;
	struct pwm_bl_data *pb;
	struct pwm_args pargs;
	int ret;

	if (!data) {
		ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
		if (ret < 0) {
			dev_err(&pdev->dev, "failed to find platform data\n");
			return ret;
		}

		data = &defdata;
	}

	if (data->init) {
		ret = data->init(&pdev->dev);
		if (ret < 0)
			return ret;
	}

	pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
	if (!pb) {
		ret = -ENOMEM;
		goto err_alloc;
	}

	if (data->levels) {
		unsigned int i;

		for (i = 0; i <= data->max_brightness; i++)
			if (data->levels[i] > pb->scale)
				pb->scale = data->levels[i];

		pb->levels = data->levels;
	} else
		pb->scale = data->max_brightness;

	pb->notify = data->notify;
	pb->notify_after = data->notify_after;
	pb->check_fb = data->check_fb;
	pb->exit = data->exit;
	pb->dev = &pdev->dev;
	pb->enabled = false;

	pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
						  GPIOD_ASIS);
	if (IS_ERR(pb->enable_gpio)) {
		ret = PTR_ERR(pb->enable_gpio);
		goto err_alloc;
	}

	/*
         * Compatibility fallback for drivers still using the integer GPIO
         * platform data. Must go away soon.
         */
	if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
		ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
					    GPIOF_OUT_INIT_HIGH, "enable");
		if (ret < 0) {
			dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
				data->enable_gpio, ret);
			goto err_alloc;
		}

		pb->enable_gpio = gpio_to_desc(data->enable_gpio);
	}

	/*
         * If the GPIO is not known to be already configured as output, that
         * is, if gpiod_get_direction returns either GPIOF_DIR_IN or -EINVAL,
         * change the direction to output and set the GPIO as active.
         * Do not force the GPIO to active when it was already output as it
         * could cause backlight flickering or we would enable the backlight too
         * early. Leave the decision of the initial backlight state for later.
         */
	if (pb->enable_gpio &&
	    gpiod_get_direction(pb->enable_gpio) != GPIOF_DIR_OUT)
		gpiod_direction_output(pb->enable_gpio, 1);

	pb->power_supply = devm_regulator_get(&pdev->dev, "power");
	if (IS_ERR(pb->power_supply)) {
		ret = PTR_ERR(pb->power_supply);
		goto err_alloc;
	}

	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) {
		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
		pb->legacy = true;
		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
	}

	if (IS_ERR(pb->pwm)) {
		ret = PTR_ERR(pb->pwm);
		if (ret != -EPROBE_DEFER)
			dev_err(&pdev->dev, "unable to request PWM\n");
		goto err_alloc;
	}

	dev_dbg(&pdev->dev, "got pwm for backlight\n");

	/*
         * FIXME: pwm_apply_args() should be removed when switching to
         * the atomic PWM API.
         */
	pwm_apply_args(pb->pwm);

	/*
         * The DT case will set the pwm_period_ns field to 0 and store the
         * period, parsed from the DT, in the PWM device. For the non-DT case,
         * set the period from platform data if it has not already been set
         * via the PWM lookup table.
         */
	pwm_get_args(pb->pwm, &pargs);
	pb->period = pargs.period;
	if (!pb->period && (data->pwm_period_ns > 0))
		pb->period = data->pwm_period_ns;

	pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);

	memset(&props, 0, sizeof(struct backlight_properties));
	props.type = BACKLIGHT_RAW;
	props.max_brightness = data->max_brightness;
	bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
				       &pwm_backlight_ops, &props);
	if (IS_ERR(bl)) {
		dev_err(&pdev->dev, "failed to register backlight\n");
		ret = PTR_ERR(bl);
		if (pb->legacy)
			pwm_free(pb->pwm);
		goto err_alloc;
	}

	if (data->dft_brightness > data->max_brightness) {
		dev_warn(&pdev->dev,
			 "invalid default brightness level: %u, using %u\n",
			 data->dft_brightness, data->max_brightness);
		data->dft_brightness = data->max_brightness;
	}

	bl->props.brightness = data->dft_brightness;
	bl->props.power = pwm_backlight_initial_power_state(pb);
	backlight_update_status(bl);

	platform_set_drvdata(pdev, bl);
	return 0;

err_alloc:
	if (data->exit)
		data->exit(&pdev->dev);
	return ret;
}

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14.89%
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67
8.04%
2
6.06%
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42
5.04%
2
6.06%
Vladimir Zapolskiy
42
5.04%
3
9.09%
Mike Dunn
40
4.80%
1
3.03%
Ben Dooks
39
4.68%
3
9.09%
Matthew Garrett
31
3.72%
2
6.06%
Boris Brezillon
23
2.76%
1
3.03%
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17
2.04%
1
3.03%
Nicolas Ferre
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1.08%
1
3.03%
Arun Murthy
8
0.96%
1
3.03%
Robert Morell
8
0.96%
1
3.03%
Dilan Lee
8
0.96%
1
3.03%
Julia Lawall
6
0.72%
1
3.03%
Jingoo Han
4
0.48%
1
3.03%
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3
0.36%
1
3.03%
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0.12%
1
3.03%
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0.12%
1
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833
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static int pwm_backlight_remove(struct platform_device *pdev)
{
	struct backlight_device *bl = platform_get_drvdata(pdev);
	struct pwm_bl_data *pb = bl_get_data(bl);

	backlight_device_unregister(bl);
	pwm_backlight_power_off(pb);

	if (pb->exit)
		pb->exit(&pdev->dev);
	if (pb->legacy)
		pwm_free(pb->pwm);

	return 0;
}

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Vladimir Zapolskiy
13
17.81%
1
16.67%
Thierry Reding
3
4.11%
2
33.33%
Jingoo Han
1
1.37%
1
16.67%
Total
73
100.00%
6
100.00%



static void pwm_backlight_shutdown(struct platform_device *pdev)
{
	struct backlight_device *bl = platform_get_drvdata(pdev);
	struct pwm_bl_data *pb = bl_get_data(bl);

	pwm_backlight_power_off(pb);
}

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#ifdef CONFIG_PM_SLEEP


static int pwm_backlight_suspend(struct device *dev)
{
	struct backlight_device *bl = dev_get_drvdata(dev);
	struct pwm_bl_data *pb = bl_get_data(bl);

	if (pb->notify)
		pb->notify(pb->dev, 0);

	pwm_backlight_power_off(pb);

	if (pb->notify_after)
		pb->notify_after(pb->dev, 0);

	return 0;
}

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4
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Mark Brown
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5.48%
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1
1.37%
1
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1
1.37%
1
14.29%
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static int pwm_backlight_resume(struct device *dev)
{
	struct backlight_device *bl = dev_get_drvdata(dev);

	backlight_update_status(bl);

	return 0;
}
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#endif


static const struct dev_pm_ops pwm_backlight_pm_ops = {
#ifdef CONFIG_PM_SLEEP
	.suspend = pwm_backlight_suspend,
	.resume = pwm_backlight_resume,
	.poweroff = pwm_backlight_suspend,
	.restore = pwm_backlight_resume,
#endif
};


static struct platform_driver pwm_backlight_driver = {
	.driver		= {
		.name		= "pwm-backlight",
		.pm		= &pwm_backlight_pm_ops,
		.of_match_table	= of_match_ptr(pwm_backlight_of_match),
        },
	.probe		= pwm_backlight_probe,
	.remove		= pwm_backlight_remove,
	.shutdown	= pwm_backlight_shutdown,
};


module_platform_driver(pwm_backlight_driver);

MODULE_DESCRIPTION("PWM based Backlight Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:pwm-backlight");
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Philipp Zabel
163
7.93%
3
6.00%
Peter Ujfalusi
130
6.33%
3
6.00%
Alexandre Courbot
83
4.04%
4
8.00%
Robert Morell
68
3.31%
1
2.00%
Ben Dooks
61
2.97%
4
8.00%
Vladimir Zapolskiy
58
2.82%
3
6.00%
Dilan Lee
56
2.73%
1
2.00%
Mike Dunn
44
2.14%
1
2.00%
Matthew Garrett
31
1.51%
2
4.00%
Huayi Li
30
1.46%
1
2.00%
Boris Brezillon
23
1.12%
1
2.00%
Arun Murthy
21
1.02%
1
2.00%
Alexandre Belloni
17
0.83%
1
2.00%
Mark Brown
17
0.83%
1
2.00%
Marc Zyngier
13
0.63%
1
2.00%
Jingoo Han
11
0.54%
3
6.00%
Nicolas Ferre
9
0.44%
1
2.00%
Lothar Waßmann
7
0.34%
1
2.00%
Julia Lawall
6
0.29%
1
2.00%
Geert Uytterhoeven
3
0.15%
1
2.00%
Tejun Heo
3
0.15%
1
2.00%
Axel Lin
2
0.10%
2
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Maxime Ripard
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Sachin Kamat
1
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Directory: drivers/video/backlight

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