backlight: add led-backlight driver
authorTomi Valkeinen <tomi.valkeinen@ti.com>
Wed, 19 Feb 2020 19:46:10 +0000 (11:46 -0800)
committerTony Lindgren <tony@atomide.com>
Wed, 19 Feb 2020 21:15:39 +0000 (13:15 -0800)
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>
Acked-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Tony Lindgren <tony@atomide.com>
Tested-by: Tony Lindgren <tony@atomide.com>
Tested-by: Guido Günther <agx@sigxcpu.org>
Signed-off-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Tony Lindgren <tony@atomide.com>
drivers/video/backlight/Kconfig
drivers/video/backlight/Makefile
drivers/video/backlight/led_bl.c [new file with mode: 0644]

index 403707a..0093bbd 100644 (file)
@@ -456,6 +456,13 @@ 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
index 6f87770..0c1a152 100644 (file)
@@ -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 (file)
index 0000000..3f66549
--- /dev/null
@@ -0,0 +1,260 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2015-2019 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/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-level", &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 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;
+       }
+
+       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 = 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");
+               return PTR_ERR(priv->bl_dev);
+       }
+
+       for (i = 0; i < priv->nb_leds; i++)
+               led_sysfs_disable(priv->leds[i]);
+
+       backlight_update_status(priv->bl_dev);
+
+       return 0;
+}
+
+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;
+       int i;
+
+       backlight_device_unregister(bl);
+
+       led_bl_power_off(priv);
+       for (i = 0; i < priv->nb_leds; i++)
+               led_sysfs_enable(priv->leds[i]);
+
+       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");