drivers/video/backlight/ktd253-backlight.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Backlight driver for the Kinetic KTD253
  * Based on code and know-how from the Samsung GT-S7710
  * Gareth Phillips <gareth.phillips@samsung.com>
  */
 #include <linux/backlight.h>
 #include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/gpio/consumer.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/limits.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/property.h>
 #include <linux/slab.h>

 /* Current ratio is n/32 from 1/32 to 32/32 */
 #define KTD253_MIN_RATIO 1
 #define KTD253_MAX_RATIO 32
 #define KTD253_DEFAULT_RATIO 13

 #define KTD253_T_LOW_NS (200 + 10) /* Additional 10ns as safety factor */
 #define KTD253_T_HIGH_NS (200 + 10) /* Additional 10ns as safety factor */
 #define KTD253_T_OFF_CRIT_NS 100000 /* 100 us, now it doesn't look good */
 #define KTD253_T_OFF_MS 3

 struct ktd253_backlight {
 	struct device *dev;
 	struct backlight_device *bl;
 	struct gpio_desc *gpiod;
 	u16 ratio;
 };

 static void ktd253_backlight_set_max_ratio(struct ktd253_backlight *ktd253)
 {
 	gpiod_set_value_cansleep(ktd253->gpiod, 1);
 	ndelay(KTD253_T_HIGH_NS);
 	/* We always fall back to this when we power on */
 }

 static int ktd253_backlight_stepdown(struct ktd253_backlight *ktd253)
 {
 	/*
 	 * These GPIO operations absolutely can NOT sleep so no _cansleep
 	 * suffixes, and no using GPIO expanders on slow buses for this!
 	 *
 	 * The maximum number of cycles of the loop is 32  so the time taken
 	 * should nominally be:
 	 * (T_LOW_NS + T_HIGH_NS + loop_time) * 32
 	 *
 	 * Architectures do not always support ndelay() and we will get a few us
 	 * instead. If we get to a critical time limit an interrupt has likely
 	 * occured in the low part of the loop and we need to restart from the
 	 * top so we have the backlight in a known state.
 	 */
 	u64 ns;

 	ns = ktime_get_ns();
 	gpiod_set_value(ktd253->gpiod, 0);
 	ndelay(KTD253_T_LOW_NS);
 	gpiod_set_value(ktd253->gpiod, 1);
 	ns = ktime_get_ns() - ns;
 	if (ns >= KTD253_T_OFF_CRIT_NS) {
 		dev_err(ktd253->dev, "PCM on backlight took too long (%llu ns)\n", ns);
 		return -EAGAIN;
 	}
 	ndelay(KTD253_T_HIGH_NS);
 	return 0;
 }

 static int ktd253_backlight_update_status(struct backlight_device *bl)
 {
 	struct ktd253_backlight *ktd253 = bl_get_data(bl);
 	int brightness = backlight_get_brightness(bl);
 	u16 target_ratio;
 	u16 current_ratio = ktd253->ratio;
 	int ret;

 	dev_dbg(ktd253->dev, "new brightness/ratio: %d/32\n", brightness);

 	target_ratio = brightness;

 	if (target_ratio == current_ratio)
 		/* This is already right */
 		return 0;

 	if (target_ratio == 0) {
 		gpiod_set_value_cansleep(ktd253->gpiod, 0);
 		/*
 		 * We need to keep the GPIO low for at least this long
 		 * to actually switch the KTD253 off.
 		 */
 		msleep(KTD253_T_OFF_MS);
 		ktd253->ratio = 0;
 		return 0;
 	}

 	if (current_ratio == 0) {
 		ktd253_backlight_set_max_ratio(ktd253);
 		current_ratio = KTD253_MAX_RATIO;
 	}

 	while (current_ratio != target_ratio) {
 		/*
 		 * These GPIO operations absolutely can NOT sleep so no
 		 * _cansleep suffixes, and no using GPIO expanders on
 		 * slow buses for this!
 		 */
 		ret = ktd253_backlight_stepdown(ktd253);
 		if (ret == -EAGAIN) {
 			/*
 			 * Something disturbed the backlight setting code when
 			 * running so we need to bring the PWM back to a known
 			 * state. This shouldn't happen too much.
 			 */
 			gpiod_set_value_cansleep(ktd253->gpiod, 0);
 			msleep(KTD253_T_OFF_MS);
 			ktd253_backlight_set_max_ratio(ktd253);
 			current_ratio = KTD253_MAX_RATIO;
 		} else if (current_ratio == KTD253_MIN_RATIO) {
 			/* After 1/32 we loop back to 32/32 */
 			current_ratio = KTD253_MAX_RATIO;
 		} else {
 			current_ratio--;
 		}
 	}
 	ktd253->ratio = current_ratio;

 	dev_dbg(ktd253->dev, "new ratio set to %d/32\n", target_ratio);

 	return 0;
 }

 static const struct backlight_ops ktd253_backlight_ops = {
 	.options	= BL_CORE_SUSPENDRESUME,
 	.update_status	= ktd253_backlight_update_status,
 };

 static int ktd253_backlight_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct backlight_device *bl;
 	struct ktd253_backlight *ktd253;
 	u32 max_brightness;
 	u32 brightness;
 	int ret;

 	ktd253 = devm_kzalloc(dev, sizeof(*ktd253), GFP_KERNEL);
 	if (!ktd253)
 		return -ENOMEM;
 	ktd253->dev = dev;

 	ret = device_property_read_u32(dev, "max-brightness", &max_brightness);
 	if (ret)
 		max_brightness = KTD253_MAX_RATIO;
 	if (max_brightness > KTD253_MAX_RATIO) {
 		/* Clamp brightness to hardware max */
 		dev_err(dev, "illegal max brightness specified\n");
 		max_brightness = KTD253_MAX_RATIO;
 	}

 	ret = device_property_read_u32(dev, "default-brightness", &brightness);
 	if (ret)
 		brightness = KTD253_DEFAULT_RATIO;
 	if (brightness > max_brightness) {
 		/* Clamp default brightness to max brightness */
 		dev_err(dev, "default brightness exceeds max brightness\n");
 		brightness = max_brightness;
 	}

 	ktd253->gpiod = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);
 	if (IS_ERR(ktd253->gpiod))
 		return dev_err_probe(dev, PTR_ERR(ktd253->gpiod),
 				     "gpio line missing or invalid.\n");
 	gpiod_set_consumer_name(ktd253->gpiod, dev_name(dev));
 	/* Bring backlight to a known off state */
 	msleep(KTD253_T_OFF_MS);

 	bl = devm_backlight_device_register(dev, dev_name(dev), dev, ktd253,
 					    &ktd253_backlight_ops, NULL);
 	if (IS_ERR(bl)) {
 		dev_err(dev, "failed to register backlight\n");
 		return PTR_ERR(bl);
 	}
 	bl->props.max_brightness = max_brightness;
 	/* When we just enable the GPIO line we set max brightness */
 	if (brightness) {
 		bl->props.brightness = brightness;
 		bl->props.power = BACKLIGHT_POWER_ON;
 	} else {
 		bl->props.brightness = 0;
 		bl->props.power = BACKLIGHT_POWER_OFF;
 	}

 	ktd253->bl = bl;
 	platform_set_drvdata(pdev, bl);
 	backlight_update_status(bl);

 	return 0;
 }

 static const struct of_device_id ktd253_backlight_of_match[] = {
 	{ .compatible = "kinetic,ktd253" },
 	{ .compatible = "kinetic,ktd259" },
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, ktd253_backlight_of_match);

 static struct platform_driver ktd253_backlight_driver = {
 	.driver = {
 		.name = "ktd253-backlight",
 		.of_match_table = ktd253_backlight_of_match,
 	},
 	.probe		= ktd253_backlight_probe,
 };
 module_platform_driver(ktd253_backlight_driver);

 MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
 MODULE_DESCRIPTION("Kinetic KTD253 Backlight Driver");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS("platform:ktd253-backlight");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Backlight driver for the Kinetic KTD253
	* Based on code and know-how from the Samsung GT-S7710
	* Gareth Phillips <gareth.phillips@samsung.com>
	*/
	#include <linux/backlight.h>
	#include <linux/delay.h>
	#include <linux/err.h>
	#include <linux/gpio/consumer.h>
	#include <linux/init.h>
	#include <linux/kernel.h>
	#include <linux/limits.h>
	#include <linux/module.h>
	#include <linux/of.h>
	#include <linux/platform_device.h>
	#include <linux/property.h>
	#include <linux/slab.h>

	/* Current ratio is n/32 from 1/32 to 32/32 */
	#define KTD253_MIN_RATIO 1
	#define KTD253_MAX_RATIO 32
	#define KTD253_DEFAULT_RATIO 13

	#define KTD253_T_LOW_NS (200 + 10) /* Additional 10ns as safety factor */
	#define KTD253_T_HIGH_NS (200 + 10) /* Additional 10ns as safety factor */
	#define KTD253_T_OFF_CRIT_NS 100000 /* 100 us, now it doesn't look good */
	#define KTD253_T_OFF_MS 3

	struct ktd253_backlight {
	struct device *dev;
	struct backlight_device *bl;
	struct gpio_desc *gpiod;
	u16 ratio;
	};

	static void ktd253_backlight_set_max_ratio(struct ktd253_backlight *ktd253)
	{
	gpiod_set_value_cansleep(ktd253->gpiod, 1);
	ndelay(KTD253_T_HIGH_NS);
	/* We always fall back to this when we power on */
	}

	static int ktd253_backlight_stepdown(struct ktd253_backlight *ktd253)
	{
	/*
	* These GPIO operations absolutely can NOT sleep so no _cansleep
	* suffixes, and no using GPIO expanders on slow buses for this!
	*
	* The maximum number of cycles of the loop is 32 so the time taken
	* should nominally be:
	* (T_LOW_NS + T_HIGH_NS + loop_time) * 32
	*
	* Architectures do not always support ndelay() and we will get a few us
	* instead. If we get to a critical time limit an interrupt has likely
	* occured in the low part of the loop and we need to restart from the
	* top so we have the backlight in a known state.
	*/
	u64 ns;

	ns = ktime_get_ns();
	gpiod_set_value(ktd253->gpiod, 0);
	ndelay(KTD253_T_LOW_NS);
	gpiod_set_value(ktd253->gpiod, 1);
	ns = ktime_get_ns() - ns;
	if (ns >= KTD253_T_OFF_CRIT_NS) {
	dev_err(ktd253->dev, "PCM on backlight took too long (%llu ns)\n", ns);
	return -EAGAIN;
	}
	ndelay(KTD253_T_HIGH_NS);
	return 0;
	}

	static int ktd253_backlight_update_status(struct backlight_device *bl)
	{
	struct ktd253_backlight *ktd253 = bl_get_data(bl);
	int brightness = backlight_get_brightness(bl);
	u16 target_ratio;
	u16 current_ratio = ktd253->ratio;
	int ret;

	dev_dbg(ktd253->dev, "new brightness/ratio: %d/32\n", brightness);

	target_ratio = brightness;

	if (target_ratio == current_ratio)
	/* This is already right */
	return 0;

	if (target_ratio == 0) {
	gpiod_set_value_cansleep(ktd253->gpiod, 0);
	/*
	* We need to keep the GPIO low for at least this long
	* to actually switch the KTD253 off.
	*/
	msleep(KTD253_T_OFF_MS);
	ktd253->ratio = 0;
	return 0;
	}

	if (current_ratio == 0) {
	ktd253_backlight_set_max_ratio(ktd253);
	current_ratio = KTD253_MAX_RATIO;
	}

	while (current_ratio != target_ratio) {
	/*
	* These GPIO operations absolutely can NOT sleep so no
	* _cansleep suffixes, and no using GPIO expanders on
	* slow buses for this!
	*/
	ret = ktd253_backlight_stepdown(ktd253);
	if (ret == -EAGAIN) {
	/*
	* Something disturbed the backlight setting code when
	* running so we need to bring the PWM back to a known
	* state. This shouldn't happen too much.
	*/
	gpiod_set_value_cansleep(ktd253->gpiod, 0);
	msleep(KTD253_T_OFF_MS);
	ktd253_backlight_set_max_ratio(ktd253);
	current_ratio = KTD253_MAX_RATIO;
	} else if (current_ratio == KTD253_MIN_RATIO) {
	/* After 1/32 we loop back to 32/32 */
	current_ratio = KTD253_MAX_RATIO;
	} else {
	current_ratio--;
	}
	}
	ktd253->ratio = current_ratio;

	dev_dbg(ktd253->dev, "new ratio set to %d/32\n", target_ratio);

	return 0;
	}

	static const struct backlight_ops ktd253_backlight_ops = {
	.options = BL_CORE_SUSPENDRESUME,
	.update_status = ktd253_backlight_update_status,
	};

	static int ktd253_backlight_probe(struct platform_device *pdev)
	{
	struct device *dev = &pdev->dev;
	struct backlight_device *bl;
	struct ktd253_backlight *ktd253;
	u32 max_brightness;
	u32 brightness;
	int ret;

	ktd253 = devm_kzalloc(dev, sizeof(*ktd253), GFP_KERNEL);
	if (!ktd253)
	return -ENOMEM;
	ktd253->dev = dev;

	ret = device_property_read_u32(dev, "max-brightness", &max_brightness);
	if (ret)
	max_brightness = KTD253_MAX_RATIO;
	if (max_brightness > KTD253_MAX_RATIO) {
	/* Clamp brightness to hardware max */
	dev_err(dev, "illegal max brightness specified\n");
	max_brightness = KTD253_MAX_RATIO;
	}

	ret = device_property_read_u32(dev, "default-brightness", &brightness);
	if (ret)
	brightness = KTD253_DEFAULT_RATIO;
	if (brightness > max_brightness) {
	/* Clamp default brightness to max brightness */
	dev_err(dev, "default brightness exceeds max brightness\n");
	brightness = max_brightness;
	}

	ktd253->gpiod = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);
	if (IS_ERR(ktd253->gpiod))
	return dev_err_probe(dev, PTR_ERR(ktd253->gpiod),
	"gpio line missing or invalid.\n");
	gpiod_set_consumer_name(ktd253->gpiod, dev_name(dev));
	/* Bring backlight to a known off state */
	msleep(KTD253_T_OFF_MS);

	bl = devm_backlight_device_register(dev, dev_name(dev), dev, ktd253,
	&ktd253_backlight_ops, NULL);
	if (IS_ERR(bl)) {
	dev_err(dev, "failed to register backlight\n");
	return PTR_ERR(bl);
	}
	bl->props.max_brightness = max_brightness;
	/* When we just enable the GPIO line we set max brightness */
	if (brightness) {
	bl->props.brightness = brightness;
	bl->props.power = BACKLIGHT_POWER_ON;
	} else {
	bl->props.brightness = 0;
	bl->props.power = BACKLIGHT_POWER_OFF;
	}

	ktd253->bl = bl;
	platform_set_drvdata(pdev, bl);
	backlight_update_status(bl);

	return 0;
	}

	static const struct of_device_id ktd253_backlight_of_match[] = {
	{ .compatible = "kinetic,ktd253" },
	{ .compatible = "kinetic,ktd259" },
	{ /* sentinel */ }
	};
	MODULE_DEVICE_TABLE(of, ktd253_backlight_of_match);

	static struct platform_driver ktd253_backlight_driver = {
	.driver = {
	.name = "ktd253-backlight",
	.of_match_table = ktd253_backlight_of_match,
	},
	.probe = ktd253_backlight_probe,
	};
	module_platform_driver(ktd253_backlight_driver);

	MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
	MODULE_DESCRIPTION("Kinetic KTD253 Backlight Driver");
	MODULE_LICENSE("GPL");
	MODULE_ALIAS("platform:ktd253-backlight");