1 files changed, 707 insertions, 0 deletions

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
new file mode 100644
index 000000000..c0523a026
--- /dev/null
+++ b/drivers/video/backlight/pwm_bl.c
@@ -0,0 +1,707 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Simple PWM based backlight control, board code has to setup
+ * 1) pin configuration so PWM waveforms can output
+ * 2) platform_data being correctly configured
+ */
+
+#include <linux/delay.h>
+#include <linux/gpio/consumer.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		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)
+{
+	struct pwm_state state;
+	int err;
+
+	pwm_get_state(pb->pwm, &state);
+	if (pb->enabled)
+		return;
+
+	err = regulator_enable(pb->power_supply);
+	if (err < 0)
+		dev_err(pb->dev, "failed to enable power supply\n");
+
+	state.enabled = true;
+	pwm_apply_state(pb->pwm, &state);
+
+	if (pb->post_pwm_on_delay)
+		msleep(pb->post_pwm_on_delay);
+
+	if (pb->enable_gpio)
+		gpiod_set_value_cansleep(pb->enable_gpio, 1);
+
+	pb->enabled = true;
+}
+
+static void pwm_backlight_power_off(struct pwm_bl_data *pb)
+{
+	struct pwm_state state;
+
+	pwm_get_state(pb->pwm, &state);
+	if (!pb->enabled)
+		return;
+
+	if (pb->enable_gpio)
+		gpiod_set_value_cansleep(pb->enable_gpio, 0);
+
+	if (pb->pwm_off_delay)
+		msleep(pb->pwm_off_delay);
+
+	state.enabled = false;
+	state.duty_cycle = 0;
+	pwm_apply_state(pb->pwm, &state);
+
+	regulator_disable(pb->power_supply);
+	pb->enabled = false;
+}
+
+static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
+{
+	unsigned int lth = pb->lth_brightness;
+	struct pwm_state state;
+	u64 duty_cycle;
+
+	pwm_get_state(pb->pwm, &state);
+
+	if (pb->levels)
+		duty_cycle = pb->levels[brightness];
+	else
+		duty_cycle = brightness;
+
+	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 = backlight_get_brightness(bl);
+	struct pwm_state state;
+
+	if (pb->notify)
+		brightness = pb->notify(pb->dev, brightness);
+
+	if (brightness > 0) {
+		pwm_get_state(pb->pwm, &state);
+		state.duty_cycle = compute_duty_cycle(pb, brightness);
+		pwm_apply_state(pb->pwm, &state);
+		pwm_backlight_power_on(pb);
+	} else {
+		pwm_backlight_power_off(pb);
+	}
+
+	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;
+
+	if (!node)
+		return -ENODEV;
+
+	memset(data, 0, sizeof(*data));
+
+	/*
+	 * 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 0;
+
+	num_levels = length / sizeof(u32);
+
+	/* read brightness levels from DT property */
+	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,
+						 num_levels);
+		if (ret < 0)
+			return ret;
+
+		ret = of_property_read_u32(node, "default-brightness-level",
+					   &value);
+		if (ret < 0)
+			return ret;
+
+		data->dft_brightness = value;
+
+		/*
+		 * 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;
+	}
+
+	return 0;
+}
+
+static const 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;
+}
+
+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 (!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.
+	 */
+	if (pb->enable_gpio)
+		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;
+
+	/*
+	 * 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.
+	 */
+	return active ? FB_BLANK_UNBLANK: FB_BLANK_POWERDOWN;
+}
+
+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_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;
+		}
+
+		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;
+	}
+
+	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);
+		goto err_alloc;
+	}
+
+	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");
+
+	/* 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
+	 * 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.
+	 */
+	if (!state.period && (data->pwm_period_ns > 0))
+		state.period = data->pwm_period_ns;
+
+	ret = pwm_apply_state(pb->pwm, &state);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to apply initial PWM state: %d\n",
+			ret);
+		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(&pdev->dev,
+				"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);
+		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;
+}
+
+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;
+}
+
+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);
+}
+
+#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;
+}
+
+static int pwm_backlight_resume(struct device *dev)
+{
+	struct backlight_device *bl = dev_get_drvdata(dev);
+
+	backlight_update_status(bl);
+
+	return 0;
+}
+#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 v2");
+MODULE_ALIAS("platform:pwm-backlight");