backlight: Add Kinetic KTD2801 backlight support

KTD2801 is a LED backlight driver IC found in samsung,coreprimevelte.
The brightness can be set using PWM or the ExpressWire protocol. Add
support for the KTD2801.

Signed-off-by: Duje Mihanović <duje.mihanovic@skole.hr>

diff --git a/MAINTAINERS b/MAINTAINERS
index 647b9614dc731d68ced99a2337645085e5dce129..e8a0e342a0dcf98350691bd115f2df4714270650 100644 (file)
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11900,6 +11900,12 @@ S:     Maintained
 F:     Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml
 F:     drivers/video/backlight/ktd253-backlight.c
 
+KTD2801 BACKLIGHT DRIVER
+M:     Duje Mihanović <duje.mihanovic@skole.hr>
+S:     Maintained
+F:     Documentation/devicetree/bindings/leds/backlight/kinetic,ktd2801.yaml
+F:     drivers/video/backlight/ktd2801-backlight.c
+
 KTEST
 M:     Steven Rostedt <rostedt@goodmis.org>
 M:     John Hawley <warthog9@eaglescrag.net>

diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index 51387b1ef012a118c9ad54c2d19bf97d58805d65..585a5a713759c1603cb88e7ddfba25a69440b0f7 100644 (file)
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -183,6 +183,14 @@ config BACKLIGHT_KTD253
          which is a 1-wire GPIO-controlled backlight found in some mobile
          phones.
 
+config BACKLIGHT_KTD2801
+       tristate "Backlight Driver for Kinetic KTD2801"
+       depends on GPIOLIB || COMPILE_TEST
+       select LEDS_EXPRESSWIRE
+       help
+         Say Y to enable the backlight driver for the Kinetic KTD2801 1-wire
+         GPIO-controlled backlight found in Samsung Galaxy Core Prime VE LTE.
+
 config BACKLIGHT_KTZ8866
        tristate "Backlight Driver for Kinetic KTZ8866"
        depends on I2C

diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index f72e1c3c59e956a0e175429822884bef3497adcd..b33b647f31ca140ab2103cdf0f3b9b1415bcf03d 100644 (file)
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -35,6 +35,7 @@ obj-$(CONFIG_BACKLIGHT_HP680)         += hp680_bl.o
 obj-$(CONFIG_BACKLIGHT_HP700)          += jornada720_bl.o
 obj-$(CONFIG_BACKLIGHT_IPAQ_MICRO)     += ipaq_micro_bl.o
 obj-$(CONFIG_BACKLIGHT_KTD253)         += ktd253-backlight.o
+obj-$(CONFIG_BACKLIGHT_KTD2801)                += ktd2801-backlight.o
 obj-$(CONFIG_BACKLIGHT_KTZ8866)                += ktz8866.o
 obj-$(CONFIG_BACKLIGHT_LM3533)         += lm3533_bl.o
 obj-$(CONFIG_BACKLIGHT_LM3630A)                += lm3630a_bl.o

diff --git a/drivers/video/backlight/ktd2801-backlight.c b/drivers/video/backlight/ktd2801-backlight.c
new file mode 100644 (file)
index 0000000..7b9d1a9
--- /dev/null
+++ b/drivers/video/backlight/ktd2801-backlight.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Datasheet:
+ * https://www.kinet-ic.com/uploads/web/KTD2801/KTD2801-04b.pdf
+ */
+#include <linux/backlight.h>
+#include <linux/bits.h>
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/leds-expresswire.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+
+/* These values have been extracted from Samsung's driver. */
+#define KTD2801_EXPRESSWIRE_DETECT_DELAY_US    150
+#define KTD2801_EXPRESSWIRE_DETECT_US          270
+#define KTD2801_SHORT_BITSET_US                        5
+#define KTD2801_LONG_BITSET_US                 (3 * KTD2801_SHORT_BITSET_US)
+#define KTD2801_DATA_START_US                  5
+#define KTD2801_END_OF_DATA_LOW_US             10
+#define KTD2801_END_OF_DATA_HIGH_US            350
+#define KTD2801_PWR_DOWN_DELAY_US              2600
+
+#define KTD2801_DEFAULT_BRIGHTNESS     100
+#define KTD2801_MAX_BRIGHTNESS         255
+
+const struct expresswire_timing ktd2801_timing = {
+       .poweroff_us = KTD2801_PWR_DOWN_DELAY_US,
+       .detect_delay_us = KTD2801_EXPRESSWIRE_DETECT_DELAY_US,
+       .detect_us = KTD2801_EXPRESSWIRE_DETECT_US,
+       .data_start_us = KTD2801_DATA_START_US,
+       .short_bitset_us = KTD2801_SHORT_BITSET_US,
+       .long_bitset_us = KTD2801_LONG_BITSET_US,
+       .end_of_data_low_us = KTD2801_END_OF_DATA_LOW_US,
+       .end_of_data_high_us = KTD2801_END_OF_DATA_HIGH_US
+};
+
+struct ktd2801_backlight {
+       struct expresswire_common_props props;
+       struct backlight_device *bd;
+       bool was_on;
+};
+
+static int ktd2801_update_status(struct backlight_device *bd)
+{
+       struct ktd2801_backlight *ktd2801 = bl_get_data(bd);
+       u8 brightness = (u8) backlight_get_brightness(bd);
+
+       if (backlight_is_blank(bd)) {
+               expresswire_power_off(&ktd2801->props);
+               ktd2801->was_on = false;
+               return 0;
+       }
+
+       if (!ktd2801->was_on) {
+               expresswire_enable(&ktd2801->props);
+               ktd2801->was_on = true;
+       }
+
+       expresswire_start(&ktd2801->props);
+
+       for (int i = 7; i >= 0; i--)
+               expresswire_set_bit(&ktd2801->props, !!(brightness & BIT(i)));
+
+       expresswire_end(&ktd2801->props);
+       return 0;
+}
+
+static const struct backlight_ops ktd2801_backlight_ops = {
+       .update_status = ktd2801_update_status,
+};
+
+static int ktd2801_backlight_probe(struct platform_device *pdev)
+{
+       struct device *dev = &pdev->dev;
+       struct backlight_device *bd;
+       struct ktd2801_backlight *ktd2801;
+       u32 brightness, max_brightness;
+       int ret;
+
+       ktd2801 = devm_kzalloc(dev, sizeof(*ktd2801), GFP_KERNEL);
+       if (!ktd2801)
+               return -ENOMEM;
+       ktd2801->was_on = true;
+       ktd2801->props.timing = ktd2801_timing;
+
+       ret = device_property_read_u32(dev, "max-brightness", &max_brightness);
+       if (ret)
+               max_brightness = KTD2801_MAX_BRIGHTNESS;
+       if (max_brightness > KTD2801_MAX_BRIGHTNESS) {
+               dev_err(dev, "illegal max brightness specified\n");
+               max_brightness = KTD2801_MAX_BRIGHTNESS;
+       }
+
+       ret = device_property_read_u32(dev, "default-brightness", &brightness);
+       if (ret)
+               brightness = KTD2801_DEFAULT_BRIGHTNESS;
+       if (brightness > max_brightness) {
+               dev_err(dev, "default brightness exceeds max\n");
+               brightness = max_brightness;
+       }
+
+       ktd2801->props.ctrl_gpio = devm_gpiod_get(dev, "ctrl", GPIOD_OUT_HIGH);
+       if (IS_ERR(ktd2801->props.ctrl_gpio))
+               return dev_err_probe(dev, PTR_ERR(ktd2801->props.ctrl_gpio),
+                               "failed to get backlight GPIO");
+       gpiod_set_consumer_name(ktd2801->props.ctrl_gpio, dev_name(dev));
+
+       bd = devm_backlight_device_register(dev, dev_name(dev), dev, ktd2801,
+                       &ktd2801_backlight_ops, NULL);
+       if (IS_ERR(bd))
+               return dev_err_probe(dev, PTR_ERR(bd),
+                               "failed to register backlight");
+
+       bd->props.max_brightness = max_brightness;
+       bd->props.brightness = brightness;
+
+       ktd2801->bd = bd;
+       platform_set_drvdata(pdev, bd);
+       backlight_update_status(bd);
+
+       return 0;
+}
+
+static const struct of_device_id ktd2801_of_match[] = {
+       { .compatible = "kinetic,ktd2801" },
+       { }
+};
+MODULE_DEVICE_TABLE(of, ktd2801_of_match);
+
+static struct platform_driver ktd2801_backlight_driver = {
+       .driver = {
+               .name = "ktd2801-backlight",
+               .of_match_table = ktd2801_of_match,
+       },
+       .probe = ktd2801_backlight_probe,
+};
+module_platform_driver(ktd2801_backlight_driver);
+
+MODULE_IMPORT_NS(EXPRESSWIRE);
+MODULE_AUTHOR("Duje Mihanović <duje.mihanovic@skole.hr>");
+MODULE_DESCRIPTION("Kinetic KTD2801 Backlight Driver");
+MODULE_LICENSE("GPL");