backlight: add led-backlight driver

From: Tomi Valkeinen <[email protected]>

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 <[email protected]>

Signed-off-by Jean-Jacques Hiblot <[email protected]>

Acked-by Pavel Machek <[email protected]>

Reviewed-by Daniel Thompson <[email protected]>

Acked-by Lee Jones <[email protected]>

Acked-by Tony Lindgren <[email protected]>

Tested-by Tony Lindgren <[email protected]>

Signed-off-by Pavel Machek <[email protected]>

---
 drivers/video/backlight/Kconfig  |   7 ++
 drivers/video/backlight/Makefile |   1 +
 drivers/video/backlight/led_bl.c | 260 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 268 insertions(+)
 create mode 100644 drivers/video/backlight/led_bl.c

Hi!

Here's the version of the driver I have. AFAICT default-brightness-level handling is ok, so does not need to be changed.

Lee, it would be easiest for me if you could apply it to your tree and push, but given enough time I can push it to Linus, too.

Quoted 19 lines

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 <[email protected]>

Signed-off-by Jean-Jacques Hiblot <[email protected]>

Acked-by Pavel Machek <[email protected]>

Reviewed-by Daniel Thompson <[email protected]>

Acked-by Lee Jones <[email protected]>

Acked-by Tony Lindgren <[email protected]>

Tested-by Tony Lindgren <[email protected]>

Signed-off-by Pavel Machek <[email protected]>

---
 drivers/video/backlight/Kconfig  |   7 ++
 drivers/video/backlight/Makefile |   1 +
 drivers/video/backlight/led_bl.c | 260 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 268 insertions(+)
 create mode 100644 drivers/video/backlight/led_bl.c

Quoted 6 lines

Here's the version of the driver I have. AFAICT default-brightness-level handling is ok, so does not need to be changed.

Lee, it would be easiest for me if you could apply it to your tree and push, but given enough time I can push it to Linus, too.

Oh you're using quoted-printable for patches.. Got it applied now, and it still works. Below is also the related dts change that I tested with.

Feel free to pick the dts change too, naturally that should not be applied before the driver.

If you guys instead want me to pick these both into my fixes branch, just let me know and I'll do the explaining why these are needed as fixes. Basically we no longer have a way to enable the LCD backlight for droid4 manually starting with v5.6-rc1 unlike earlier.

Hi!

Quoted 33 lines

Quoted 19 lines

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 <[email protected]>

Signed-off-by Jean-Jacques Hiblot <[email protected]>

Acked-by Pavel Machek <[email protected]>

Reviewed-by Daniel Thompson <[email protected]>

Acked-by Lee Jones <[email protected]>

Acked-by Tony Lindgren <[email protected]>

Tested-by Tony Lindgren <[email protected]>

Signed-off-by Pavel Machek <[email protected]>

---
 drivers/video/backlight/Kconfig  |   7 ++
 drivers/video/backlight/Makefile |   1 +
 drivers/video/backlight/led_bl.c | 260 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 268 insertions(+)
 create mode 100644 drivers/video/backlight/led_bl.c

Quoted 6 lines

Here's the version of the driver I have. AFAICT default-brightness-level handling is ok, so does not need to be changed.

Lee, it would be easiest for me if you could apply it to your tree and push, but given enough time I can push it to Linus, too.

Oh you're using quoted-printable for patches.. Got it applied now, and it still works. Below is also the related dts change that I tested with.

Feel free to pick the dts change too, naturally that should not be applied before the driver.

Quoted 5 lines

If you guys instead want me to pick these both into my fixes branch, just let me know and I'll do the explaining why these are needed as fixes. Basically we no longer have a way to enable the LCD backlight for droid4 manually starting with v5.6-rc1 unlike earlier.

If you are willing to do that, it looks like good solution from my point of view.

Quoted 6 lines

Quoted 5 lines

If you guys instead want me to pick these both into my fixes branch, just let me know and I'll do the explaining why these are needed as fixes. Basically we no longer have a way to enable the LCD backlight for droid4 manually starting with v5.6-rc1 unlike earlier.

Quoted 2 lines

If you are willing to do that, it looks like good solution from my point of view.

OK. I'll apply them but won't push out yet in case Lee is already applying the driver change..

Pavel, care to ack the dts patch?

Quoted 21 lines · Pavel Machek

From: Tomi Valkeinen <[email protected]>

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 <[email protected]>

Signed-off-by Jean-Jacques Hiblot <[email protected]>

Acked-by Pavel Machek <[email protected]>

Reviewed-by Daniel Thompson <[email protected]>

Acked-by Lee Jones <[email protected]>

Acked-by Tony Lindgren <[email protected]>

Tested-by Tony Lindgren <[email protected]>

Signed-off-by Pavel Machek <[email protected]>

---
 drivers/video/backlight/Kconfig  |   7 ++
 drivers/video/backlight/Makefile |   1 +
 drivers/video/backlight/led_bl.c | 260 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 268 insertions(+)
 create mode 100644 drivers/video/backlight/led_bl.c

Quoted 8 lines

Hi!

Here's the version of the driver I have. AFAICT default-brightness-level handling is ok, so does not need to be changed.

Lee, it would be easiest for me if you could apply it to your tree and push, but given enough time I can push it to Linus, too.

Oh you're using quoted-printable for patches.. Got it applied now, and it still works. Below is also the related dts change that I tested with.

Feel free to pick the dts change too, naturally that should not be applied before the driver.

If you guys instead want me to pick these both into my fixes branch, just let me know and I'll do the explaining why these are needed as fixes. Basically we no longer have a way to enable the LCD backlight for droid4 manually starting with v5.6-rc1 unlike earlier.

Regards,

Tony

8< ------------------
From tony Mon Sep 17 00:00:00 2001
From: Tony Lindgren <[email protected]>
Date: Wed, 19 Feb 2020 11:25:27 -0800
Subject: [PATCH] ARM: dts: droid4: Configure LED backlight for lm3532

With the LED backlight changes merged, we still need the dts configured to have backlight working for droid4. Based on an earlier patch from Pavel Machek <[email protected]>, let's configure the backlight but update the value range to be more usable.

We have a range of 256 register values split into 8 steps, so we can generate the brightness levels backwards with:

$ for i in 0 1 2 3 4 5 6 7; do echo "255 - ${i} * (256 / 8)" | bc; done

To avoid more confusion why the LCD backlight is still not on, let's also enable LED backlight as a loadable module for omap2plus_defconfig.

Cc Merlijn Wajer <[email protected]>

Cc Pavel Machek <[email protected]>

Signed-off-by Tony Lindgren <[email protected]>

---
 arch/arm/boot/dts/motorola-mapphone-common.dtsi | 13 +++++++++++--
 arch/arm/configs/omap2plus_defconfig            |  1 +
 2 files changed, 12 insertions(+), 2 deletions(-)

arch/arm/boot/dts/motorola-mapphone-common.dtsi +11 -2

@@ -182,6 +182,14 @@ vibrator {
 		pwm-names = "enable", "direction";
 		direction-duty-cycle-ns = <10000000>;
 	};
+
+	backlight: backlight {
+		compatible = "led-backlight";
+
+		leds = <&backlight_led>;
+		brightness-levels = <31 63 95 127 159 191 223 255>;
+		default-brightness-level = <6>;
+	};
 };
 
 &dss {

@@ -205,6 +213,8 @@ lcd0: display {
 		vddi-supply = <&lcd_regulator>;
 		reset-gpios = <&gpio4 5 GPIO_ACTIVE_HIGH>;	/* gpio101 */
 
+		backlight = <&backlight>;
+
 		width-mm = <50>;
 		height-mm = <89>;
 

@@ -393,12 +403,11 @@ led-controller@38 {
 		ramp-up-us = <1024>;
 		ramp-down-us = <8193>;
 
-		led@0 {
+		backlight_led: led@0 {
 			reg = <0>;
 			led-sources = <2>;
 			ti,led-mode = <0>;
 			label = ":backlight";
-			linux,default-trigger = "backlight";
 		};
 
 		led@1 {

Finally :)

Reviewed-by Sebastian Reichel <[email protected]>

Quoted 21 lines · Pavel Machek

From: Tomi Valkeinen <[email protected]>

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 <[email protected]>

Signed-off-by Jean-Jacques Hiblot <[email protected]>

Acked-by Pavel Machek <[email protected]>

Reviewed-by Daniel Thompson <[email protected]>

Acked-by Lee Jones <[email protected]>

Acked-by Tony Lindgren <[email protected]>

Tested-by Tony Lindgren <[email protected]>

Signed-off-by Pavel Machek <[email protected]>

---
 drivers/video/backlight/Kconfig  |   7 ++
 drivers/video/backlight/Makefile |   1 +
 drivers/video/backlight/led_bl.c | 260 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 268 insertions(+)
 create mode 100644 drivers/video/backlight/led_bl.c

Quoted 8 lines

Hi!

Here's the version of the driver I have. AFAICT default-brightness-level handling is ok, so does not need to be changed.

Lee, it would be easiest for me if you could apply it to your tree and push, but given enough time I can push it to Linus, too.

Oh you're using quoted-printable for patches.. Got it applied now, and it still works. Below is also the related dts change that I tested with.

Feel free to pick the dts change too, naturally that should not be applied before the driver.

If you guys instead want me to pick these both into my fixes branch, just let me know and I'll do the explaining why these are needed as fixes. Basically we no longer have a way to enable the LCD backlight for droid4 manually starting with v5.6-rc1 unlike earlier.

Quoted 38 lines · Tony Lindgren

Quoted 21 lines · Pavel Machek

From: Tomi Valkeinen <[email protected]>

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 <[email protected]>

Signed-off-by Jean-Jacques Hiblot <[email protected]>

Acked-by Pavel Machek <[email protected]>

Reviewed-by Daniel Thompson <[email protected]>

Acked-by Lee Jones <[email protected]>

Acked-by Tony Lindgren <[email protected]>

Tested-by Tony Lindgren <[email protected]>

Signed-off-by Pavel Machek <[email protected]>

---
 drivers/video/backlight/Kconfig  |   7 ++
 drivers/video/backlight/Makefile |   1 +
 drivers/video/backlight/led_bl.c | 260 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 268 insertions(+)
 create mode 100644 drivers/video/backlight/led_bl.c

Quoted 8 lines

Hi!

Here's the version of the driver I have. AFAICT default-brightness-level handling is ok, so does not need to be changed.

Lee, it would be easiest for me if you could apply it to your tree and push, but given enough time I can push it to Linus, too.

Oh you're using quoted-printable for patches.. Got it applied now, and it still works. Below is also the related dts change that I tested with.

Feel free to pick the dts change too, naturally that should not be applied before the driver.

Quoted 5 lines

If you guys instead want me to pick these both into my fixes branch, just let me know and I'll do the explaining why these are needed as fixes. Basically we no longer have a way to enable the LCD backlight for droid4 manually starting with v5.6-rc1 unlike earlier.

Please do. You already have my Ack.

From: Tomi Valkeinen <[email protected]>

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 <[email protected]>

Signed-off-by Jean-Jacques Hiblot <[email protected]>

Acked-by Pavel Machek <[email protected]>

Reviewed-by Daniel Thompson <[email protected]>

Acked-by Lee Jones <[email protected]>

Acked-by Tony Lindgren <[email protected]>

Tested-by Tony Lindgren <[email protected]>

Signed-off-by Pavel Machek <[email protected]>

---
 drivers/video/backlight/Kconfig  |   7 ++
 drivers/video/backlight/Makefile |   1 +
 drivers/video/backlight/led_bl.c | 260 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 268 insertions(+)
 create mode 100644 drivers/video/backlight/led_bl.c

Hi!

Here's the version of the driver I have. AFAICT default-brightness-level handling is ok, so does not need to be changed.

Lee, it would be easiest for me if you could apply it to your tree and push, but given enough time I can push it to Linus, too.

Thanks,
Pavel

drivers/video/backlight/Kconfig +7 -0

index 403707a3e503..0093bbd0d326 100644
@@ -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

drivers/video/backlight/Makefile +1 -0

index 6f8777037c37..0c1a1524627a 100644
@@ -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

drivers/video/backlight/led_bl.c new file +260 -0

new file mode 100644
index 000000000000..3f66549997c8
@@ -0,0 +1,260 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2015-2019 Texas Instruments Incorporated -  http://www.ti.com/
+ * Author: Tomi Valkeinen <[email protected]>
+ *
+ * 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");

Signature · 1 line

2.11.0

Quoted 3 lines

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.

Tested-by Guido Günther <[email protected]>

Hi!

Quoted 5 lines

Quoted 3 lines

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.

Tested-by Guido Günther <[email protected]>

Thanks for testing!

I noticed blog post about using Librem 5 torch. Unfortunately, it used very strange/non-standard interface, first using LED as a GPIO to enable LED controller, then direct i2c access. That is not acceptable interface for mainline, and it would be better not to advertise such code, as it will likely become broken in future.

Quoted 6 lines

Quoted 5 lines

Quoted 3 lines

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.

Tested-by Guido Günther <[email protected]>

Quoted 7 lines

Thanks for testing!

I noticed blog post about using Librem 5 torch. Unfortunately, it used very strange/non-standard interface, first using LED as a GPIO to enable LED controller, then direct i2c access. That is not acceptable interface for mainline, and it would be better not to advertise such code, as it will likely become broken in future.

I agree, there's a driver for the lm3560 in media/ but how would one expose the torch part as a LED? It seems you hit something similar in

    https://lkml.org/lkml/2018/5/6/30

I also couldn't find an in tree driver that registers a flashlight as a v4l subdev. Did i miss that?