1 files changed, 399 insertions, 151 deletions

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 002f1ce22bd0..237d3d3f3bb1 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -1,22 +1,16 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
- * linux/drivers/video/backlight/pwm_bl.c
- *
- * simple PWM based backlight control, board code has to setup
+ * 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/delay.h>
 #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>
@@ -27,37 +21,39 @@
 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;
+	unsigned int		post_pwm_on_delay;
+	unsigned int		pwm_off_delay;
 	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)
+static void pwm_backlight_power_on(struct pwm_bl_data *pb)
 {
 	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->power_supply) {
+		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);
+	if (pb->post_pwm_on_delay)
+		msleep(pb->post_pwm_on_delay);
+
+	gpiod_set_value_cansleep(pb->enable_gpio, 1);
 
-	pwm_enable(pb->pwm);
 	pb->enabled = true;
 }
 
@@ -66,75 +62,167 @@ 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);
+	gpiod_set_value_cansleep(pb->enable_gpio, 0);
 
-	if (pb->enable_gpio)
-		gpiod_set_value_cansleep(pb->enable_gpio, 0);
+	if (pb->pwm_off_delay)
+		msleep(pb->pwm_off_delay);
 
-	regulator_disable(pb->power_supply);
+	if (pb->power_supply)
+		regulator_disable(pb->power_supply);
 	pb->enabled = false;
 }
 
-static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
+static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness, struct pwm_state *state)
 {
 	unsigned int lth = pb->lth_brightness;
-	int duty_cycle;
+	u64 duty_cycle;
 
 	if (pb->levels)
 		duty_cycle = pb->levels[brightness];
 	else
 		duty_cycle = brightness;
 
-	return (duty_cycle * (pb->period - lth) / pb->scale) + lth;
+	duty_cycle *= state->period - lth;
+	do_div(duty_cycle, pb->scale);
+
+	return duty_cycle + lth;
 }
 
 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;
+	int brightness = backlight_get_brightness(bl);
+	struct pwm_state state;
 
 	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_get_state(pb->pwm, &state);
+		state.duty_cycle = compute_duty_cycle(pb, brightness, &state);
+		state.enabled = true;
+		pwm_apply_might_sleep(pb->pwm, &state);
+
+		pwm_backlight_power_on(pb);
+	} else {
 		pwm_backlight_power_off(pb);
 
+		pwm_get_state(pb->pwm, &state);
+		state.duty_cycle = 0;
+		/*
+		 * We cannot assume a disabled PWM to drive its output to the
+		 * inactive state. If we have an enable GPIO and/or a regulator
+		 * we assume that this isn't relevant and we can disable the PWM
+		 * to save power. If however there is neither an enable GPIO nor
+		 * a regulator keep the PWM on be sure to get a constant
+		 * inactive output.
+		 */
+		state.enabled = !pb->power_supply && !pb->enable_gpio;
+		pwm_apply_might_sleep(pb->pwm, &state);
+	}
+
 	if (pb->notify_after)
 		pb->notify_after(pb->dev, brightness);
 
 	return 0;
 }
 
-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);
-}
-
 static const struct backlight_ops pwm_backlight_ops = {
 	.update_status	= pwm_backlight_update_status,
-	.check_fb	= pwm_backlight_check_fb,
 };
 
 #ifdef CONFIG_OF
+#define PWM_LUMINANCE_SHIFT	16
+#define PWM_LUMINANCE_SCALE	(1 << PWM_LUMINANCE_SHIFT) /* luminance scale */
+
+/*
+ * CIE lightness to PWM conversion.
+ *
+ * The CIE 1931 lightness formula is what actually describes how we perceive
+ * light:
+ *          Y = (L* / 903.3)           if L* ≤ 8
+ *          Y = ((L* + 16) / 116)^3    if L* > 8
+ *
+ * Where Y is the luminance, the amount of light coming out of the screen, and
+ * is a number between 0.0 and 1.0; and L* is the lightness, how bright a human
+ * perceives the screen to be, and is a number between 0 and 100.
+ *
+ * The following function does the fixed point maths needed to implement the
+ * above formula.
+ */
+static u64 cie1931(unsigned int lightness)
+{
+	u64 retval;
+
+	/*
+	 * @lightness is given as a number between 0 and 1, expressed
+	 * as a fixed-point number in scale
+	 * PWM_LUMINANCE_SCALE. Convert to a percentage, still
+	 * expressed as a fixed-point number, so the above formulas
+	 * can be applied.
+	 */
+	lightness *= 100;
+	if (lightness <= (8 * PWM_LUMINANCE_SCALE)) {
+		retval = DIV_ROUND_CLOSEST(lightness * 10, 9033);
+	} else {
+		retval = (lightness + (16 * PWM_LUMINANCE_SCALE)) / 116;
+		retval *= retval * retval;
+		retval += 1ULL << (2*PWM_LUMINANCE_SHIFT - 1);
+		retval >>= 2*PWM_LUMINANCE_SHIFT;
+	}
+
+	return retval;
+}
+
+/*
+ * Create a default correction table for PWM values to create linear brightness
+ * for LED based backlights using the CIE1931 algorithm.
+ */
+static
+int pwm_backlight_brightness_default(struct device *dev,
+				     struct platform_pwm_backlight_data *data,
+				     unsigned int period)
+{
+	unsigned int i;
+	u64 retval;
+
+	/*
+	 * Once we have 4096 levels there's little point going much higher...
+	 * neither interactive sliders nor animation benefits from having
+	 * more values in the table.
+	 */
+	data->max_brightness =
+		min((int)DIV_ROUND_UP(period, fls(period)), 4096);
+
+	data->levels = devm_kcalloc(dev, data->max_brightness,
+				    sizeof(*data->levels), GFP_KERNEL);
+	if (!data->levels)
+		return -ENOMEM;
+
+	/* Fill the table using the cie1931 algorithm */
+	for (i = 0; i < data->max_brightness; i++) {
+		retval = cie1931((i * PWM_LUMINANCE_SCALE) /
+				 data->max_brightness) * period;
+		retval = DIV_ROUND_CLOSEST_ULL(retval, PWM_LUMINANCE_SCALE);
+		if (retval > UINT_MAX)
+			return -EINVAL;
+		data->levels[i] = (unsigned int)retval;
+	}
+
+	data->dft_brightness = data->max_brightness / 2;
+	data->max_brightness--;
+
+	return 0;
+}
+
 static int pwm_backlight_parse_dt(struct device *dev,
 				  struct platform_pwm_backlight_data *data)
 {
 	struct device_node *node = dev->of_node;
+	unsigned int num_levels;
+	unsigned int num_steps = 0;
 	struct property *prop;
+	unsigned int *table;
 	int length;
 	u32 value;
 	int ret;
@@ -144,24 +232,34 @@ static int pwm_backlight_parse_dt(struct device *dev,
 
 	memset(data, 0, sizeof(*data));
 
-	/* determine the number of brightness levels */
+	/*
+	 * These values are optional and set as 0 by default, the out values
+	 * are modified only if a valid u32 value can be decoded.
+	 */
+	of_property_read_u32(node, "post-pwm-on-delay-ms",
+			     &data->post_pwm_on_delay);
+	of_property_read_u32(node, "pwm-off-delay-ms", &data->pwm_off_delay);
+
+	/*
+	 * Determine the number of brightness levels, if this property is not
+	 * set a default table of brightness levels will be used.
+	 */
 	prop = of_find_property(node, "brightness-levels", &length);
 	if (!prop)
-		return -EINVAL;
+		return 0;
 
-	data->max_brightness = length / sizeof(u32);
+	num_levels = 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 (num_levels > 0) {
+		data->levels = devm_kcalloc(dev, num_levels,
+					    sizeof(*data->levels), GFP_KERNEL);
 		if (!data->levels)
 			return -ENOMEM;
 
 		ret = of_property_read_u32_array(node, "brightness-levels",
 						 data->levels,
-						 data->max_brightness);
+						 num_levels);
 		if (ret < 0)
 			return ret;
 
@@ -171,14 +269,85 @@ static int pwm_backlight_parse_dt(struct device *dev,
 			return ret;
 
 		data->dft_brightness = value;
-		data->max_brightness--;
+
+		/*
+		 * This property is optional, if is set enables linear
+		 * interpolation between each of the values of brightness levels
+		 * and creates a new pre-computed table.
+		 */
+		of_property_read_u32(node, "num-interpolated-steps",
+				     &num_steps);
+
+		/*
+		 * Make sure that there is at least two entries in the
+		 * brightness-levels table, otherwise we can't interpolate
+		 * between two points.
+		 */
+		if (num_steps) {
+			unsigned int num_input_levels = num_levels;
+			unsigned int i;
+			u32 x1, x2, x, dx;
+			u32 y1, y2;
+			s64 dy;
+
+			if (num_input_levels < 2) {
+				dev_err(dev, "can't interpolate\n");
+				return -EINVAL;
+			}
+
+			/*
+			 * Recalculate the number of brightness levels, now
+			 * taking in consideration the number of interpolated
+			 * steps between two levels.
+			 */
+			num_levels = (num_input_levels - 1) * num_steps + 1;
+			dev_dbg(dev, "new number of brightness levels: %d\n",
+				num_levels);
+
+			/*
+			 * Create a new table of brightness levels with all the
+			 * interpolated steps.
+			 */
+			table = devm_kcalloc(dev, num_levels, sizeof(*table),
+					     GFP_KERNEL);
+			if (!table)
+				return -ENOMEM;
+			/*
+			 * Fill the interpolated table[x] = y
+			 * by draw lines between each (x1, y1) to (x2, y2).
+			 */
+			dx = num_steps;
+			for (i = 0; i < num_input_levels - 1; i++) {
+				x1 = i * dx;
+				x2 = x1 + dx;
+				y1 = data->levels[i];
+				y2 = data->levels[i + 1];
+				dy = (s64)y2 - y1;
+
+				for (x = x1; x < x2; x++) {
+					table[x] = y1 +
+						div_s64(dy * (x - x1), dx);
+				}
+			}
+			/* Fill in the last point, since no line starts here. */
+			table[x2] = y2;
+
+			/*
+			 * As we use interpolation lets remove current
+			 * brightness levels table and replace for the
+			 * new interpolated table.
+			 */
+			devm_kfree(dev, data->levels);
+			data->levels = table;
+		}
+
+		data->max_brightness = num_levels - 1;
 	}
 
-	data->enable_gpio = -EINVAL;
 	return 0;
 }
 
-static struct of_device_id pwm_backlight_of_match[] = {
+static const struct of_device_id pwm_backlight_of_match[] = {
 	{ .compatible = "pwm-backlight" },
 	{ }
 };
@@ -190,15 +359,74 @@ static int pwm_backlight_parse_dt(struct device *dev,
 {
 	return -ENODEV;
 }
+
+static
+int pwm_backlight_brightness_default(struct device *dev,
+				     struct platform_pwm_backlight_data *data,
+				     unsigned int period)
+{
+	return -ENODEV;
+}
 #endif
 
+static bool pwm_backlight_is_linear(struct platform_pwm_backlight_data *data)
+{
+	unsigned int nlevels = data->max_brightness + 1;
+	unsigned int min_val = data->levels[0];
+	unsigned int max_val = data->levels[nlevels - 1];
+	/*
+	 * Multiplying by 128 means that even in pathological cases such
+	 * as (max_val - min_val) == nlevels the error at max_val is less
+	 * than 1%.
+	 */
+	unsigned int slope = (128 * (max_val - min_val)) / nlevels;
+	unsigned int margin = (max_val - min_val) / 20; /* 5% */
+	int i;
+
+	for (i = 1; i < nlevels; i++) {
+		unsigned int linear_value = min_val + ((i * slope) / 128);
+		unsigned int delta = abs(linear_value - data->levels[i]);
+
+		if (delta > margin)
+			return false;
+	}
+
+	return true;
+}
+
 static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
 {
 	struct device_node *node = pb->dev->of_node;
+	bool active = true;
+
+	/*
+	 * If the enable GPIO is present, observable (either as input
+	 * or output) and off then the backlight is not currently active.
+	 * */
+	if (pb->enable_gpio && gpiod_get_value_cansleep(pb->enable_gpio) == 0)
+		active = false;
+
+	if (pb->power_supply && !regulator_is_enabled(pb->power_supply))
+		active = false;
+
+	if (!pwm_is_enabled(pb->pwm))
+		active = false;
+
+	/*
+	 * Synchronize the enable_gpio with the observed state of the
+	 * hardware.
+	 */
+	gpiod_direction_output(pb->enable_gpio, active);
+
+	/*
+	 * Do not change pb->enabled here! pb->enabled essentially
+	 * tells us if we own one of the regulator's use counts and
+	 * right now we do not.
+	 */
 
 	/* Not booted with device tree or no phandle link to the node */
 	if (!node || !node->phandle)
-		return FB_BLANK_UNBLANK;
+		return BACKLIGHT_POWER_ON;
 
 	/*
 	 * If the driver is probed from the device tree and there is a
@@ -206,20 +434,7 @@ static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
 	 * 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;
+	return active ? BACKLIGHT_POWER_ON : BACKLIGHT_POWER_OFF;
 }
 
 static int pwm_backlight_probe(struct platform_device *pdev)
@@ -228,17 +443,16 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 	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;
+	struct pwm_state state;
+	unsigned int i;
 	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;
-		}
+		if (ret < 0)
+			return dev_err_probe(&pdev->dev, ret,
+					     "failed to find platform data\n");
 
 		data = &defdata;
 	}
@@ -255,86 +469,45 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 		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->post_pwm_on_delay = data->post_pwm_on_delay;
+	pb->pwm_off_delay = data->pwm_off_delay;
 
 	pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
 						  GPIOD_ASIS);
 	if (IS_ERR(pb->enable_gpio)) {
-		ret = PTR_ERR(pb->enable_gpio);
+		ret = dev_err_probe(&pdev->dev, PTR_ERR(pb->enable_gpio),
+				    "failed to acquire enable GPIO\n");
 		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");
+	pb->power_supply = devm_regulator_get_optional(&pdev->dev, "power");
 	if (IS_ERR(pb->power_supply)) {
 		ret = PTR_ERR(pb->power_supply);
-		goto err_alloc;
+		if (ret == -ENODEV) {
+			pb->power_supply = NULL;
+		} else {
+			dev_err_probe(&pdev->dev, ret,
+				      "failed to acquire power regulator\n");
+			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");
+		ret = dev_err_probe(&pdev->dev, PTR_ERR(pb->pwm),
+				    "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);
+	/* Sync up PWM state. */
+	pwm_init_state(pb->pwm, &state);
 
 	/*
 	 * The DT case will set the pwm_period_ns field to 0 and store the
@@ -342,23 +515,80 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 	 * 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;
+	if (!state.period && (data->pwm_period_ns > 0))
+		state.period = data->pwm_period_ns;
 
-	pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
+	ret = pwm_apply_might_sleep(pb->pwm, &state);
+	if (ret) {
+		dev_err_probe(&pdev->dev, ret,
+			      "failed to apply initial PWM state");
+		goto err_alloc;
+	}
 
 	memset(&props, 0, sizeof(struct backlight_properties));
+
+	if (data->levels) {
+		pb->levels = data->levels;
+
+		/*
+		 * For the DT case, only when brightness levels is defined
+		 * data->levels is filled. For the non-DT case, data->levels
+		 * can come from platform data, however is not usual.
+		 */
+		for (i = 0; i <= data->max_brightness; i++)
+			if (data->levels[i] > pb->scale)
+				pb->scale = data->levels[i];
+
+		if (pwm_backlight_is_linear(data))
+			props.scale = BACKLIGHT_SCALE_LINEAR;
+		else
+			props.scale = BACKLIGHT_SCALE_NON_LINEAR;
+	} else if (!data->max_brightness) {
+		/*
+		 * If no brightness levels are provided and max_brightness is
+		 * not set, use the default brightness table. For the DT case,
+		 * max_brightness is set to 0 when brightness levels is not
+		 * specified. For the non-DT case, max_brightness is usually
+		 * set to some value.
+		 */
+
+		/* Get the PWM period (in nanoseconds) */
+		pwm_get_state(pb->pwm, &state);
+
+		ret = pwm_backlight_brightness_default(&pdev->dev, data,
+						       state.period);
+		if (ret < 0) {
+			dev_err_probe(&pdev->dev, ret,
+				      "failed to setup default brightness table\n");
+			goto err_alloc;
+		}
+
+		for (i = 0; i <= data->max_brightness; i++) {
+			if (data->levels[i] > pb->scale)
+				pb->scale = data->levels[i];
+
+			pb->levels = data->levels;
+		}
+
+		props.scale = BACKLIGHT_SCALE_NON_LINEAR;
+	} else {
+		/*
+		 * That only happens for the non-DT case, where platform data
+		 * sets the max_brightness value.
+		 */
+		pb->scale = data->max_brightness;
+	}
+
+	pb->lth_brightness = data->lth_brightness * (div_u64(state.period,
+				pb->scale));
+
 	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);
+		ret = dev_err_probe(&pdev->dev, PTR_ERR(bl),
+				    "failed to register backlight\n");
 		goto err_alloc;
 	}
 
@@ -382,28 +612,34 @@ err_alloc:
 	return ret;
 }
 
-static int pwm_backlight_remove(struct platform_device *pdev)
+static void pwm_backlight_remove(struct platform_device *pdev)
 {
 	struct backlight_device *bl = platform_get_drvdata(pdev);
 	struct pwm_bl_data *pb = bl_get_data(bl);
+	struct pwm_state state;
 
 	backlight_device_unregister(bl);
 	pwm_backlight_power_off(pb);
+	pwm_get_state(pb->pwm, &state);
+	state.duty_cycle = 0;
+	state.enabled = false;
+	pwm_apply_might_sleep(pb->pwm, &state);
 
 	if (pb->exit)
 		pb->exit(&pdev->dev);
-	if (pb->legacy)
-		pwm_free(pb->pwm);
-
-	return 0;
 }
 
 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);
+	struct pwm_state state;
 
 	pwm_backlight_power_off(pb);
+	pwm_get_state(pb->pwm, &state);
+	state.duty_cycle = 0;
+	state.enabled = false;
+	pwm_apply_might_sleep(pb->pwm, &state);
 }
 
 #ifdef CONFIG_PM_SLEEP
@@ -411,12 +647,24 @@ 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);
+	struct pwm_state state;
 
 	if (pb->notify)
 		pb->notify(pb->dev, 0);
 
 	pwm_backlight_power_off(pb);
 
+	/*
+	 * Note that disabling the PWM doesn't guarantee that the output stays
+	 * at its inactive state. However without the PWM disabled, the PWM
+	 * driver refuses to suspend. So disable here even though this might
+	 * enable the backlight on poorly designed boards.
+	 */
+	pwm_get_state(pb->pwm, &state);
+	state.duty_cycle = 0;
+	state.enabled = false;
+	pwm_apply_might_sleep(pb->pwm, &state);
+
 	if (pb->notify_after)
 		pb->notify_after(pb->dev, 0);
 
@@ -456,5 +704,5 @@ static struct platform_driver pwm_backlight_driver = {
 module_platform_driver(pwm_backlight_driver);
 
 MODULE_DESCRIPTION("PWM based Backlight Driver");
-MODULE_LICENSE("GPL");
+MODULE_LICENSE("GPL v2");
 MODULE_ALIAS("platform:pwm-backlight");