From c541b4c80043848ff19e4906ecfc49c6f6818198 Mon Sep 17 00:00:00 2001
From: Potato <nikko@faint.day>
Date: Mon, 2 Oct 2023 15:14:09 +0800
Subject: [PATCH 1/6] video: backlight: Add OCP8178 backlight driver

This driver is taken from
https://github.com/clockworkpi/DevTerm/blob/main/Code/patch/armbian_build_a06/patch/kernel-005-backlight.patch
and optimized for v6.5.
---
 drivers/video/backlight/Kconfig      |   6 +
 drivers/video/backlight/Makefile     |   1 +
 drivers/video/backlight/ocp8178_bl.c | 245 +++++++++++++++++++++++++++
 3 files changed, 252 insertions(+)
 create mode 100644 drivers/video/backlight/ocp8178_bl.c

diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index 0e66152b02e6..efb66e7abb85 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -484,6 +484,12 @@ config BACKLIGHT_LED
 	  If you have a LCD backlight adjustable by LED class driver, say Y
 	  to enable this driver.
 
+config BACKLIGHT_OCP8178
+	tristate "OCP8178 Backlight Driver"
+	depends on GPIOLIB || COMPILE_TEST
+	help
+	  If you have an OCP8178, say Y to enable the backlight driver.
+
 endif # BACKLIGHT_CLASS_DEVICE
 
 endmenu
diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index ac878b4fb0ee..4d431321f1f2 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -60,3 +60,4 @@ 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
+obj-$(CONFIG_BACKLIGHT_OCP8178)		+= ocp8178_bl.o
diff --git a/drivers/video/backlight/ocp8178_bl.c b/drivers/video/backlight/ocp8178_bl.c
new file mode 100644
index 000000000000..2b0d1b159500
--- /dev/null
+++ b/drivers/video/backlight/ocp8178_bl.c
@@ -0,0 +1,245 @@
+/*
+ * ocp8178_bl.c - ocp8178 backlight driver
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/backlight.h>
+#include <linux/err.h>
+#include <linux/fb.h>
+#include <linux/gpio/consumer.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/delay.h>
+
+struct ocp8178_backlight {
+	struct device *dev;
+	struct device *fbdev;
+
+	struct gpio_desc *gpiod;
+	int def_value;
+	int current_value;
+};
+
+#define DETECT_DELAY 200
+#define DETECT_TIME 500
+#define DETECT_WINDOW_TIME 1000
+#define START_TIME 10
+#define END_TIME 10
+#define SHUTDOWN_TIME 3000
+#define LOW_BIT_HIGH_TIME 10
+#define LOW_BIT_LOW_TIME 50
+#define HIGH_BIT_HIGH_TIME 50
+#define HIGH_BIT_LOW_TIME 10
+#define MAX_BRIGHTNESS_VALUE 9
+
+static void entry_1wire_mode(struct ocp8178_backlight *gbl)
+{
+	unsigned long flags = 0;
+	local_irq_save(flags);
+	gpiod_set_value(gbl->gpiod, 0);
+	mdelay(SHUTDOWN_TIME/1000);
+	gpiod_set_value(gbl->gpiod, 1);
+	udelay(DETECT_DELAY);
+	gpiod_set_value(gbl->gpiod, 0);
+	udelay(DETECT_TIME);
+	gpiod_set_value(gbl->gpiod, 1);
+	udelay(DETECT_WINDOW_TIME);
+	local_irq_restore(flags);
+}
+
+static inline void write_bit(struct ocp8178_backlight *gbl, int bit)
+{
+	if (bit) {
+		gpiod_set_value(gbl->gpiod, 0);
+		udelay(HIGH_BIT_LOW_TIME);
+		gpiod_set_value(gbl->gpiod, 1);
+		udelay(HIGH_BIT_HIGH_TIME);
+	} else {
+		gpiod_set_value(gbl->gpiod, 0);
+		udelay(LOW_BIT_LOW_TIME);
+		gpiod_set_value(gbl->gpiod, 1);
+		udelay(LOW_BIT_HIGH_TIME);
+	}
+}
+
+static void write_byte(struct ocp8178_backlight *gbl, int byte)
+{
+	unsigned long flags = 0;
+	unsigned char data = 0x72;
+	int i;
+
+	local_irq_save(flags);
+
+	gpiod_set_value(gbl->gpiod, 1);
+	udelay(START_TIME);
+	for(i = 0; i < 8; i++) {
+		if(data & 0x80) {
+			write_bit(gbl, 1);
+		} else {
+			write_bit(gbl, 0);
+		}
+		data <<= 1;
+	}
+	gpiod_set_value(gbl->gpiod, 0);
+	udelay(END_TIME);
+
+	data = byte & 0x1f;
+
+	gpiod_set_value(gbl->gpiod, 1);
+	udelay(START_TIME);
+	for(i = 0; i < 8; i++) {
+		if(data & 0x80) {
+			write_bit(gbl, 1);
+		} else {
+			write_bit(gbl, 0);
+		}
+		data <<= 1;
+	}
+	gpiod_set_value(gbl->gpiod, 0);
+	udelay(END_TIME);
+	gpiod_set_value(gbl->gpiod, 1);
+
+	local_irq_restore(flags);
+}
+
+unsigned char ocp8178_bl_table[MAX_BRIGHTNESS_VALUE+1] = {0, 1, 4, 8, 12, 16, 20, 24, 28, 31};
+
+static int ocp8178_update_status(struct backlight_device *bl)
+{
+	struct ocp8178_backlight *gbl = bl_get_data(bl);
+	int brightness = bl->props.brightness, i;
+
+	if (bl->props.power != FB_BLANK_UNBLANK ||
+	    bl->props.fb_blank != FB_BLANK_UNBLANK ||
+	    bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
+		brightness = 0;
+
+	if(brightness > MAX_BRIGHTNESS_VALUE)
+		brightness = MAX_BRIGHTNESS_VALUE;
+
+	for(i = 0; i < 2; i++) {
+		entry_1wire_mode(gbl);
+		write_byte(gbl, ocp8178_bl_table[brightness]);
+	}
+	gbl->current_value = brightness;
+
+	return 0;
+}
+
+static int ocp8178_get_brightness(struct backlight_device *bl)
+{
+	struct ocp8178_backlight *gbl = bl_get_data(bl);
+	return gbl->current_value;
+}
+
+static int ocp8178_check_fb(struct backlight_device *bl,
+				   struct fb_info *info)
+{
+	struct ocp8178_backlight *gbl = bl_get_data(bl);
+	return gbl->fbdev == NULL || gbl->fbdev == info->dev;
+}
+
+static const struct backlight_ops ocp8178_backlight_ops = {
+	.options	= BL_CORE_SUSPENDRESUME,
+	.update_status	= ocp8178_update_status,
+	.get_brightness = ocp8178_get_brightness,
+	.check_fb	= ocp8178_check_fb,
+};
+
+static int ocp8178_probe_dt(struct platform_device *pdev,
+				   struct ocp8178_backlight *gbl)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *of_node = dev->of_node;
+	enum gpiod_flags flags;
+	int ret = 0;
+	u32 default_brightness;
+
+	of_property_read_u32(of_node, "default-brightness", &default_brightness);
+	if(default_brightness > MAX_BRIGHTNESS_VALUE)
+		gbl->def_value = MAX_BRIGHTNESS_VALUE;
+	else
+		gbl->def_value = default_brightness;
+	flags = gbl->def_value ? GPIOD_OUT_HIGH : GPIOD_OUT_LOW;
+
+	gbl->gpiod = devm_gpiod_get(dev, "backlight-control", flags);
+	if (IS_ERR(gbl->gpiod)) {
+		ret = PTR_ERR(gbl->gpiod);
+		return dev_err_probe(dev, ret,
+			"Error: The backlight-control-gpios parameter is missing or invalid.\n");
+	}
+
+	return ret;
+}
+
+static int ocp8178_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct backlight_properties props;
+	struct backlight_device *bl;
+	struct ocp8178_backlight *gbl;
+	struct device_node *of_node = dev->of_node;
+	int ret;
+
+	if (!of_node) {
+		dev_err(&pdev->dev,
+			"failed to find platform data or device tree node.\n");
+		return -ENODEV;
+	}
+
+	gbl = devm_kzalloc(dev, sizeof(*gbl), GFP_KERNEL);
+	if (gbl == NULL)
+		return -ENOMEM;
+
+	gbl->dev = dev;
+
+	ret = ocp8178_probe_dt(pdev, gbl);
+	if (ret)
+		return ret;
+
+	gbl->current_value = gbl->def_value;
+
+	memset(&props, 0, sizeof(props));
+	props.type = BACKLIGHT_RAW;
+	props.max_brightness = MAX_BRIGHTNESS_VALUE;
+	bl = devm_backlight_device_register(&pdev->dev, dev_name(&pdev->dev),
+					&pdev->dev, gbl, &ocp8178_backlight_ops,
+					&props);
+	if (IS_ERR(bl)) {
+		dev_err(&pdev->dev, "failed to register backlight\n");
+		return PTR_ERR(bl);
+	}
+
+	bl->props.brightness = gbl->def_value;
+	backlight_update_status(bl);
+
+	platform_set_drvdata(pdev, bl);
+	return 0;
+}
+
+static struct of_device_id ocp8178_of_match[] = {
+	{ .compatible = "ocp8178-backlight" },
+	{ /* sentinel */ }
+};
+
+MODULE_DEVICE_TABLE(of, ocp8178_of_match);
+
+static struct platform_driver ocp8178_driver = {
+	.driver		= {
+		.name		= "ocp8178-backlight",
+		.of_match_table = of_match_ptr(ocp8178_of_match),
+	},
+	.probe		= ocp8178_probe,
+};
+
+module_platform_driver(ocp8178_driver);
+
+MODULE_DESCRIPTION("OCP8178 Driver");
+MODULE_LICENSE("GPL");
-- 
2.43.0

