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Subject[PATCH v10 6/6] backlight: add led-backlight driver
Date
From: Tomi Valkeinen <tomi.valkeinen@ti.com>

This patch adds a led-backlight driver (led_bl), which is similar to
pwm_bl except the driver uses a LED class driver to adjust the
brightness in the HW. Multiple LEDs can be used for a single backlight.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
---
drivers/video/backlight/Kconfig | 7 +
drivers/video/backlight/Makefile | 1 +
drivers/video/backlight/led_bl.c | 258 +++++++++++++++++++++++++++++++
3 files changed, 266 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..718fa3e03eac
--- /dev/null
+++ b/drivers/video/backlight/led_bl.c
@@ -0,0 +1,258 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2015-2019 Texas Instruments Incorporated - http://www.ti.com/
+ * Authors: Tomi Valkeinen <tomi.valkeinen@ti.com>
+ * Jean-Jacques Hiblot <jjhiblot@ti.com>
+ */
+
+#include <linux/backlight.h>
+#include <linux/leds.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+struct led_bl_data {
+ struct device *dev;
+ struct backlight_device *bl_dev;
+ struct led_classdev **leds;
+ bool enabled;
+ int nb_leds;
+ unsigned int *levels;
+ unsigned int default_brightness;
+ unsigned int max_brightness;
+};
+
+static void led_bl_set_brightness(struct led_bl_data *priv, int level)
+{
+ int i;
+ int bkl_brightness;
+
+ if (priv->levels)
+ bkl_brightness = priv->levels[level];
+ else
+ bkl_brightness = level;
+
+ for (i = 0; i < priv->nb_leds; i++)
+ led_set_brightness(priv->leds[i], bkl_brightness);
+
+ priv->enabled = true;
+}
+
+static void led_bl_power_off(struct led_bl_data *priv)
+{
+ int i;
+
+ if (!priv->enabled)
+ return;
+
+ for (i = 0; i < priv->nb_leds; i++)
+ led_set_brightness(priv->leds[i], LED_OFF);
+
+ 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_get_leds(struct device *dev,
+ struct led_bl_data *priv)
+{
+ int i, nb_leds, ret;
+ struct device_node *node = dev->of_node;
+ struct led_classdev **leds;
+ unsigned int max_brightness;
+ unsigned int default_brightness;
+
+ ret = of_count_phandle_with_args(node, "leds", NULL);
+ if (ret < 0) {
+ dev_err(dev, "Unable to get led count\n");
+ return -EINVAL;
+ }
+
+ nb_leds = ret;
+ if (nb_leds < 1) {
+ dev_err(dev, "At least one LED must be specified!\n");
+ return -EINVAL;
+ }
+
+ leds = devm_kzalloc(dev, sizeof(struct led_classdev *) * nb_leds,
+ GFP_KERNEL);
+ if (!leds)
+ return -ENOMEM;
+
+ for (i = 0; i < nb_leds; i++) {
+ leds[i] = devm_of_led_get(dev, i);
+ if (IS_ERR(leds[i]))
+ return PTR_ERR(leds[i]);
+ }
+
+ /* check that the LEDs all have the same brightness range */
+ max_brightness = leds[0]->max_brightness;
+ for (i = 1; i < nb_leds; i++) {
+ if (max_brightness != leds[i]->max_brightness) {
+ dev_err(dev, "LEDs must have identical ranges\n");
+ return -EINVAL;
+ }
+ }
+
+ /* get the default brightness from the first LED from the list */
+ default_brightness = leds[0]->brightness;
+
+ priv->nb_leds = nb_leds;
+ priv->leds = leds;
+ priv->max_brightness = max_brightness;
+ priv->default_brightness = default_brightness;
+
+ return 0;
+}
+
+static int led_bl_parse_levels(struct device *dev,
+ struct led_bl_data *priv)
+{
+ struct device_node *node = dev->of_node;
+ int num_levels;
+ u32 value;
+ int ret;
+
+ if (!node)
+ return -ENODEV;
+
+ num_levels = of_property_count_u32_elems(node, "brightness-levels");
+ if (num_levels > 1) {
+ int i;
+ unsigned int db;
+ u32 *levels = NULL;
+
+ 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;
+
+ /*
+ * Try to map actual LED brightness to backlight brightness
+ * level
+ */
+ db = priv->default_brightness;
+ for (i = 0 ; i < num_levels; i++) {
+ if ((i && db > levels[i-1]) && db <= levels[i])
+ break;
+ }
+ priv->default_brightness = i;
+ priv->max_brightness = num_levels - 1;
+ priv->levels = levels;
+ } else if (num_levels >= 0)
+ dev_warn(dev, "Not enough levels defined\n");
+
+ ret = of_property_read_u32(node, "default-brightness", &value);
+ if (!ret && value <= priv->max_brightness)
+ priv->default_brightness = value;
+ else if (!ret && value > priv->max_brightness)
+ dev_warn(dev, "Invalid default brightness. Ignoring it\n");
+
+ return 0;
+}
+
+static void led_bl_cleanup(void *data)
+{
+ struct led_bl_data *priv = data;
+ int i;
+
+ led_bl_power_off(priv);
+ for (i = 0; i < priv->nb_leds; i++)
+ led_sysfs_enable(priv->leds[i]);
+}
+
+static int led_bl_probe(struct platform_device *pdev)
+{
+ struct backlight_properties props;
+ struct led_bl_data *priv;
+ int ret, i;
+
+ priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ platform_set_drvdata(pdev, priv);
+
+ priv->dev = &pdev->dev;
+
+ ret = led_bl_get_leds(&pdev->dev, priv);
+ if (ret)
+ return ret;
+
+ ret = led_bl_parse_levels(&pdev->dev, priv);
+ if (ret < 0) {
+ dev_err(&pdev->dev, "Failed to parse DT data\n");
+ return ret;
+ }
+
+ ret = devm_add_action_or_reset(&pdev->dev, led_bl_cleanup, priv);
+ if (ret)
+ return ret;
+
+ for (i = 0; i < priv->nb_leds; i++)
+ led_sysfs_disable(priv->leds[i]);
+
+ memset(&props, 0, sizeof(struct backlight_properties));
+ props.type = BACKLIGHT_RAW;
+ props.max_brightness = priv->max_brightness;
+ props.brightness = priv->default_brightness;
+ props.power = (priv->default_brightness > 0) ? FB_BLANK_POWERDOWN :
+ FB_BLANK_UNBLANK;
+ priv->bl_dev = devm_backlight_device_register(&pdev->dev,
+ 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");
+ return PTR_ERR(priv->bl_dev);
+ }
+
+ backlight_update_status(priv->bl_dev);
+
+ 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 = led_bl_of_match,
+ },
+ .probe = led_bl_probe,
+};
+
+module_platform_driver(led_bl_driver);
+
+MODULE_DESCRIPTION("LED based Backlight Driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:led-backlight");
--
2.17.1
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