1 files changed, 320 insertions, 0 deletions
diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
new file mode 100644
index 00000000..1fea6273
--- /dev/null
+++ b/drivers/video/backlight/pwm_bl.c
@@ -0,0 +1,320 @@
+/*
+ * 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/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/slab.h>
+
+struct pwm_bl_data {
+	struct pwm_device	*pwm;
+	struct device		*dev;
+	unsigned int		period;
+	unsigned int		lth_brightness;
+	unsigned int		*levels;
+	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 int pwm_backlight_update_status(struct backlight_device *bl)
+{
+	struct pwm_bl_data *pb = bl_get_data(bl);
+	int brightness = bl->props.brightness;
+	int max = bl->props.max_brightness;
+
+	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) {
+		pwm_config(pb->pwm, 0, pb->period);
+		pwm_disable(pb->pwm);
+	} else {
+		int duty_cycle;
+
+		if (pb->levels) {
+			duty_cycle = pb->levels[brightness];
+			max = pb->levels[max];
+		} else {
+			duty_cycle = brightness;
+		}
+
+		duty_cycle = pb->lth_brightness +
+		     (duty_cycle * (pb->period - pb->lth_brightness) / max);
+		pwm_config(pb->pwm, duty_cycle, pb->period);
+		pwm_enable(pb->pwm);
+	}
+
+	if (pb->notify_after)
+		pb->notify_after(pb->dev, brightness);
+
+	return 0;
+}
+
+static int pwm_backlight_get_brightness(struct backlight_device *bl)
+{
+	return bl->props.brightness;
+}
+
+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,
+	.get_brightness	= pwm_backlight_get_brightness,
+	.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--;
+	}
+
+	/*
+	 * TODO: Most users of this driver use a number of GPIOs to control
+	 *       backlight power. Support for specifying these needs to be
+	 *       added.
+	 */
+
+	return 0;
+}
+
+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;
+}
+#endif
+
+static int pwm_backlight_probe(struct platform_device *pdev)
+{
+	struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
+	struct platform_pwm_backlight_data defdata;
+	struct backlight_properties props;
+	struct backlight_device *bl;
+	struct pwm_bl_data *pb;
+	unsigned int max;
+	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) {
+		dev_err(&pdev->dev, "no memory for state\n");
+		ret = -ENOMEM;
+		goto err_alloc;
+	}
+
+	if (data->levels) {
+		max = data->levels[data->max_brightness];
+		pb->levels = data->levels;
+	} else
+		max = 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->pwm = devm_pwm_get(&pdev->dev, NULL);
+	if (IS_ERR(pb->pwm)) {
+		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
+
+		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
+		if (IS_ERR(pb->pwm)) {
+			dev_err(&pdev->dev, "unable to request legacy PWM\n");
+			ret = PTR_ERR(pb->pwm);
+			goto err_alloc;
+		}
+	}
+
+	dev_dbg(&pdev->dev, "got pwm for backlight\n");
+
+	/*
+	 * 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 (data->pwm_period_ns > 0)
+		pwm_set_period(pb->pwm, data->pwm_period_ns);
+
+	pb->period = pwm_get_period(pb->pwm);
+	pb->lth_brightness = data->lth_brightness * (pb->period / max);
+
+	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);
+		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;
+	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_config(pb->pwm, 0, pb->period);
+	pwm_disable(pb->pwm);
+	if (pb->exit)
+		pb->exit(&pdev->dev);
+	return 0;
+}
+
+#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_config(pb->pwm, 0, pb->period);
+	pwm_disable(pb->pwm);
+	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 SIMPLE_DEV_PM_OPS(pwm_backlight_pm_ops, pwm_backlight_suspend,
+			 pwm_backlight_resume);
+
+static struct platform_driver pwm_backlight_driver = {
+	.driver		= {
+		.name		= "pwm-backlight",
+		.owner		= THIS_MODULE,
+		.pm		= &pwm_backlight_pm_ops,
+		.of_match_table	= of_match_ptr(pwm_backlight_of_match),
+	},
+	.probe		= pwm_backlight_probe,
+	.remove		= pwm_backlight_remove,
+};
+
+module_platform_driver(pwm_backlight_driver);
+
+MODULE_DESCRIPTION("PWM based Backlight Driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:pwm-backlight");
+