[PATCH 3/4] backlight: add led-backlight driver

Jean-Jacques Hiblot
2019-07-01T15:14:55Z

From: Tomi Valkeinen <tomi.valkeinen@ti.com>

This patch adds a led-backlight driver (led_bl), which is mostly similar to
pwm_bl except the driver uses a LED class driver to adjust the brightness
in the HW.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
---
drivers/video/backlight/Kconfig | 7 +
drivers/video/backlight/Makefile | 1 +
drivers/video/backlight/led_bl.c | 217 +++++++++++++++++++++++++++++++
3 files changed, 225 insertions(+)
create mode 100644 drivers/video/backlight/led_bl.c

diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index 8b081d61773e..585a1787618c 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -458,6 +458,13 @@ config BACKLIGHT_RAVE_SP
help
Support for backlight control on RAVE SP device.

+config BACKLIGHT_LED
+ tristate "Generic LED based Backlight Driver"
+ depends on LEDS_CLASS && OF
+ help
+ If you have a LCD backlight adjustable by LED class driver, say Y
+ to enable this driver.
+
endif # BACKLIGHT_CLASS_DEVICE

endmenu
diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index 63c507c07437..2a67642966a5 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -57,3 +57,4 @@ obj-$(CONFIG_BACKLIGHT_TPS65217) += tps65217_bl.o
obj-$(CONFIG_BACKLIGHT_WM831X) += wm831x_bl.o
obj-$(CONFIG_BACKLIGHT_ARCXCNN) += arcxcnn_bl.o
obj-$(CONFIG_BACKLIGHT_RAVE_SP) += rave-sp-backlight.o
+obj-$(CONFIG_BACKLIGHT_LED) += led_bl.o
diff --git a/drivers/video/backlight/led_bl.c b/drivers/video/backlight/led_bl.c
new file mode 100644
index 000000000000..e699924cc2bc
--- /dev/null
+++ b/drivers/video/backlight/led_bl.c
@@ -0,0 +1,217 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2015-2018 Texas Instruments Incorporated - http://www.ti.com/
+ * Author: Tomi Valkeinen <tomi.valkeinen@ti.com>
+ *
+ * Based on pwm_bl.c
+ */
+
+#include <linux/backlight.h>
+#include <linux/gpio/consumer.h>
+#include <linux/leds.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+
+struct led_bl_data {
+ struct device *dev;
+ struct backlight_device *bl_dev;
+
+ unsigned int *levels;
+ bool enabled;
+ struct regulator *power_supply;
+ struct gpio_desc *enable_gpio;
+
+ struct led_classdev *led_cdev;
+
+ unsigned int max_brightness;
+ unsigned int default_brightness;
+};
+
+static void led_bl_set_brightness(struct led_bl_data *priv, int brightness)
+{
+ int err;
+
+ if (!priv->enabled) {
+ err = regulator_enable(priv->power_supply);
+ if (err < 0)
+ dev_err(priv->dev, "failed to enable power supply\n");
+
+ if (priv->enable_gpio)
+ gpiod_set_value_cansleep(priv->enable_gpio, 1);
+ }
+
+ led_set_brightness(priv->led_cdev, priv->levels[brightness]);
+
+ priv->enabled = true;
+}
+
+static void led_bl_power_off(struct led_bl_data *priv)
+{
+ if (!priv->enabled)
+ return;
+
+ led_set_brightness(priv->led_cdev, LED_OFF);
+
+ if (priv->enable_gpio)
+ gpiod_set_value_cansleep(priv->enable_gpio, 0);
+
+ regulator_disable(priv->power_supply);
+
+ priv->enabled = false;
+}
+
+static int led_bl_update_status(struct backlight_device *bl)
+{
+ struct led_bl_data *priv = bl_get_data(bl);
+ int brightness = bl->props.brightness;
+
+ if (bl->props.power != FB_BLANK_UNBLANK ||
+ bl->props.fb_blank != FB_BLANK_UNBLANK ||
+ bl->props.state & BL_CORE_FBBLANK)
+ brightness = 0;
+
+ if (brightness > 0)
+ led_bl_set_brightness(priv, brightness);
+ else
+ led_bl_power_off(priv);
+
+ return 0;
+}
+
+static const struct backlight_ops led_bl_ops = {
+ .update_status = led_bl_update_status,
+};
+
+static int led_bl_parse_dt(struct device *dev,
+ struct led_bl_data *priv)
+{
+ struct device_node *node = dev->of_node;
+ int num_levels;
+ u32 *levels;
+ u32 value;
+ int ret;
+
+ if (!node)
+ return -ENODEV;
+
+ num_levels = of_property_count_u32_elems(node, "brightness-levels");
+ if (num_levels < 0)
+ return num_levels;
+
+ levels = devm_kzalloc(dev, sizeof(u32) * num_levels, GFP_KERNEL);
+ if (!levels)
+ return -ENOMEM;
+
+ ret = of_property_read_u32_array(node, "brightness-levels",
+ levels,
+ num_levels);
+ if (ret < 0)
+ return ret;
+
+ ret = of_property_read_u32(node, "default-brightness-level", &value);
+ if (ret < 0)
+ return ret;
+
+ if (value >= num_levels) {
+ dev_err(dev, "invalid default-brightness-level\n");
+ return -EINVAL;
+ }
+
+ priv->levels = levels;
+ priv->max_brightness = num_levels - 1;
+ priv->default_brightness = value;
+
+ return 0;
+}
+
+static int led_bl_probe(struct platform_device *pdev)
+{
+ struct backlight_properties props;
+ struct led_bl_data *priv;
+ int ret;
+
+ priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ platform_set_drvdata(pdev, priv);
+
+ priv->dev = &pdev->dev;
+ priv->led_cdev = to_led_classdev(pdev->dev.parent);
+
+ ret = led_bl_parse_dt(&pdev->dev, priv);
+ if (ret < 0) {
+ if (ret != -EPROBE_DEFER)
+ dev_err(&pdev->dev, "failed to parse DT data\n");
+ return ret;
+ }
+
+ priv->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
+ GPIOD_OUT_LOW);
+ if (IS_ERR(priv->enable_gpio)) {
+ ret = PTR_ERR(priv->enable_gpio);
+ goto err;
+ }
+
+ priv->power_supply = devm_regulator_get(&pdev->dev, "power");
+ if (IS_ERR(priv->power_supply)) {
+ ret = PTR_ERR(priv->power_supply);
+ goto err;
+ }
+
+ memset(&props, 0, sizeof(struct backlight_properties));
+ props.type = BACKLIGHT_RAW;
+ props.max_brightness = priv->max_brightness;
+ priv->bl_dev = backlight_device_register(dev_name(&pdev->dev),
+ &pdev->dev, priv, &led_bl_ops, &props);
+ if (IS_ERR(priv->bl_dev)) {
+ dev_err(&pdev->dev, "failed to register backlight\n");
+ ret = PTR_ERR(priv->bl_dev);
+ goto err;
+ }
+
+ priv->bl_dev->props.brightness = priv->default_brightness;
+ backlight_update_status(priv->bl_dev);
+
+ return 0;
+
+err:
+
+ return ret;
+}
+
+static int led_bl_remove(struct platform_device *pdev)
+{
+ struct led_bl_data *priv = platform_get_drvdata(pdev);
+ struct backlight_device *bl = priv->bl_dev;
+
+ backlight_device_unregister(bl);
+
+ led_bl_power_off(priv);
+
+ return 0;
+}
+
+static const struct of_device_id led_bl_of_match[] = {
+ { .compatible = "led-backlight" },
+ { }
+};
+
+MODULE_DEVICE_TABLE(of, led_bl_of_match);
+
+static struct platform_driver led_bl_driver = {
+ .driver = {
+ .name = "led-backlight",
+ .of_match_table = of_match_ptr(led_bl_of_match),
+ },
+ .probe = led_bl_probe,
+ .remove = led_bl_remove,
+};
+
+module_platform_driver(led_bl_driver);
+
+MODULE_DESCRIPTION("LED based Backlight Driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:led-backlight");
--
2.17.1