--- /dev/null
+/*
+ * 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(pb->enable_gpio, 1);
+
+ pwm_enable(pb->pwm);
+ pb->enabled = true;
+}
+
+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(pb->enable_gpio, 0);
+
+ 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;
+ int duty_cycle;
+
+ if (pb->levels)
+ duty_cycle = pb->levels[brightness];
+ else
+ duty_cycle = brightness;
+
+ return (duty_cycle * (pb->period - lth) / pb->scale) + 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;
+
+ 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;
+}
+
+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
+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;
+}
+
+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 = dev_get_platdata(&pdev->dev);
+ struct platform_pwm_backlight_data defdata;
+ struct backlight_properties props;
+ struct backlight_device *bl;
+ struct pwm_bl_data *pb;
+ 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");
+ 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 (pb->enable_gpio)
+ 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)) {
+ ret = PTR_ERR(pb->pwm);
+ if (ret == -EPROBE_DEFER)
+ goto err_alloc;
+
+ 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)) {
+ 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 it has not already been set
+ * via the PWM lookup table.
+ */
+ pb->period = pwm_get_period(pb->pwm);
+ if (!pb->period && (data->pwm_period_ns > 0)) {
+ pb->period = data->pwm_period_ns;
+ pwm_set_period(pb->pwm, 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);
+ 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_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");
+MODULE_ALIAS("platform:pwm-backlight");
Code Review / kvmfornfv.git / blobdiff