[PATCH v3 1/2] dt-bindings: himax,hx8837: add HiMax HX8837 bindings

[PATCH v3 1/2] dt-bindings: himax,hx8837: add HiMax HX8837 bindings

[Lubomir Rintel]

HiMax HX8837 is a display controller used on OLPC platforms.
It controlls backlight and is able to capture and freeze a frame when
the LCD controller (and the rest of the plaform) is powered off.

What is missing here is the description of connections to the LCD
controller and the panel. Maybe it would be a good idea to plug in it
between the two in a manner described in
<Documentation/devicetree/bindings/graph.txt>.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Acked-by: Pavel Machek <pavel@ucw.cz>

---
Changes since v2:
- s/betweend/between/

Changes since v1:
- s/load-gpio/load-gpios/
- Use interrupt bindings instead of gpio for the IRQ

 .../devicetree/bindings/misc/himax,hx8837.txt  | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/misc/himax,hx8837.txt

diff --git a/Documentation/devicetree/bindings/misc/himax,hx8837.txt b/Documentation/devicetree/bindings/misc/himax,hx8837.txt
new file mode 100644
index 000000000000..d0822c679ae8
--- /dev/null
+++ b/Documentation/devicetree/bindings/misc/himax,hx8837.txt
@@ -0,0 +1,18 @@
+HX8837 Display Controller
+
+Required properties:
+- compatible: Should be "himax,hx8837".
+- reg: I2C address, must be 0x0d
+- stat-gpios: gpio specifier of DCON_STAT0 and DCON_STAT1 pins (active high)
+- load-gpios: gpio specifier of DCON_LOAD pin (active high)
+- interrupt: interrupt specifier of DCON_IRQ pin (edge falling)
+
+Example:
+	dcon@d {
+		compatible = "himax,hx8837";
+		reg = <0x0d>;
+		stat-gpios = <&gpio 100 GPIO_ACTIVE_HIGH
+			      &gpio 101 GPIO_ACTIVE_HIGH>;
+		load-gpios = <&gpio 142 GPIO_ACTIVE_HIGH>;
+		interrupts = <&gpio 124 IRQ_TYPE_EDGE_FALLING>;
+	};
-- 
2.19.1

[PATCH 2/2] misc: hx8837: add a HiMax HX8837 display controller driver

[Lubomir Rintel]

HiMax HX8837 is a display controller used on OLPC platforms. It controls
backlight and is able to capture and freeze a frame when the LCD controller
(and the rest of the plaform) is powered off.

This driver is based on the same code as drivers/staging/olpc_dcon.
I modernized it to use managed GPIO, device-tree bindings, sysfs attribtue
groups, essentially fixing the staging driver's TODO.

Why I am not removing the staging driver now is because I've hobbled off
some functionality too (with an intent to bring add it back eventually):

* I've removed parts that talk directly to the OLPC EC to turn off/on the
  power. A separate patch will make the EC expose a regulator interface
  that should be used instead.

* Some work is likely needed to make XO 1 and XO 1.5 work. Both platforms
  are DT-based and could use the same bindings, but I haven't checked
  whether the cs5535 and vx855 GPIO drivers are good enough.

What is there is the backlight control and the sysfs attributes to control
the freeze/unfreeze..

I've also renamed the driver to use the actual chip name instead of the
original name that I found too generic. This way the staging driver can be
used on XO 1 and XO 1.5 for the time being, while my XO 1.75 can utilize
this one.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Reviewed-by: Rob Herring <robh@kernel.org>

---
Changes since v2:
- s/controlls/controls/
- Rob Herring's Reviewed-by tag

Changes since v1:
- Use interrupt bindings instead of gpio for the IRQ
- Update the statement on XO 1/1.5 support in the commit message

 drivers/misc/Kconfig  |  16 +
 drivers/misc/Makefile |   1 +
 drivers/misc/hx8837.c | 741 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 758 insertions(+)
 create mode 100644 drivers/misc/hx8837.c

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 3726eacdf65d..3eb6df0ea0a4 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -513,6 +513,22 @@ config MISC_RTSX
 	tristate
 	default MISC_RTSX_PCI || MISC_RTSX_USB
 
+config HX8837_DCON
+        tristate "HiMax HX8837 Display Controller on OLPC"
+        depends on I2C
+        depends on BACKLIGHT_LCD_SUPPORT
+        select BACKLIGHT_CLASS_DEVICE
+        help
+          In order to support very low power operation, the OLPC XO laptop uses a
+          secondary Display Controller, or DCON.  This secondary controller
+          is present in the video pipeline between the primary display
+          controller (integrate into the processor or chipset) and the LCD
+          panel.  It allows the main processor/display controller to be
+          completely powered off while still retaining an image on the display.
+          This controller is only available on OLPC platforms.
+
+          Unless you have an OLPC XO laptop, you will want to say N.
+
 source "drivers/misc/c2port/Kconfig"
 source "drivers/misc/eeprom/Kconfig"
 source "drivers/misc/cb710/Kconfig"
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index af22bbc3d00c..33689ae496b4 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -58,3 +58,4 @@ obj-$(CONFIG_ASPEED_LPC_SNOOP)	+= aspeed-lpc-snoop.o
 obj-$(CONFIG_PCI_ENDPOINT_TEST)	+= pci_endpoint_test.o
 obj-$(CONFIG_OCXL)		+= ocxl/
 obj-$(CONFIG_MISC_RTSX)		+= cardreader/
+obj-$(CONFIG_HX8837_DCON)	+= hx8837.o
diff --git a/drivers/misc/hx8837.c b/drivers/misc/hx8837.c
new file mode 100644
index 000000000000..cff02ed54de3
--- /dev/null
+++ b/drivers/misc/hx8837.c
@@ -0,0 +1,741 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Mainly by David Woodhouse, somewhat modified by Jordan Crouse.
+ * Modernized to use managed GPIO, device-tree, etc. by Lubomir Rintel.
+ *
+ * Copyright (C) 2006-2007  Red Hat, Inc.
+ * Copyright (C) 2006-2007  Advanced Micro Devices, Inc.
+ * Copyright (C) 2009       VIA Technology, Inc.
+ * Copyright (C) 2010-2011  Andres Salomon <dilinger@queued.net>
+ * Copyright (C) 2018       Lubomir Rintel <lkundrak@v3.sk>
+ */
+
+#include <linux/module.h>
+#include <linux/backlight.h>
+#include <linux/console.h>
+#include <linux/ctype.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/fb.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/notifier.h>
+#include <linux/reboot.h>
+
+/* DCON registers */
+
+#define DCON_REG_ID		 0
+#define DCON_REG_MODE		 1
+
+#define MODE_PASSTHRU		BIT(0)
+#define MODE_SLEEP		BIT(1)
+#define MODE_SLEEP_AUTO		BIT(2)
+#define MODE_BL_ENABLE		BIT(3)
+#define MODE_BLANK		BIT(4)
+#define MODE_CSWIZZLE		BIT(5)
+#define MODE_COL_AA		BIT(6)
+#define MODE_MONO_LUMA		BIT(7)
+#define MODE_SCAN_INT		BIT(8)
+#define MODE_CLOCKDIV		BIT(9)
+#define MODE_DEBUG		BIT(14)
+#define MODE_SELFTEST		BIT(15)
+
+#define DCON_REG_HRES		0x2
+#define DCON_REG_HTOTAL		0x3
+#define DCON_REG_HSYNC_WIDTH	0x4
+#define DCON_REG_VRES		0x5
+#define DCON_REG_VTOTAL		0x6
+#define DCON_REG_VSYNC_WIDTH	0x7
+#define DCON_REG_TIMEOUT	0x8
+#define DCON_REG_SCAN_INT	0x9
+#define DCON_REG_BRIGHT		0xa
+#define DCON_REG_MEM_OPT_A	0x41
+#define DCON_REG_MEM_OPT_B	0x42
+
+/* Load Delay Locked Loop (DLL) settings for clock delay */
+#define MEM_DLL_CLOCK_DELAY	BIT(0)
+/* Memory controller power down function */
+#define MEM_POWER_DOWN		BIT(8)
+/* Memory controller software reset */
+#define MEM_SOFT_RESET		BIT(0)
+
+/* Status values */
+
+#define DCONSTAT_SCANINT	0
+#define DCONSTAT_SCANINT_DCON	1
+#define DCONSTAT_DISPLAYLOAD	2
+#define DCONSTAT_MISSED		3
+
+/* Source values */
+
+#define DCON_SOURCE_DCON        0
+#define DCON_SOURCE_CPU         1
+
+struct hx8837_priv {
+	struct i2c_client *client;
+	struct fb_info *fbinfo;
+	struct backlight_device *bl_dev;
+
+	wait_queue_head_t waitq;
+	struct work_struct switch_source;
+	struct notifier_block reboot_nb;
+	struct notifier_block panic_nb;
+
+	/* Scanline to interrupt on during resume */
+	ushort resumeline;
+
+	/* Shadow register for the DCON_REG_MODE register */
+	u8 disp_mode;
+
+	/* The current backlight value - this saves us some smbus traffic */
+	u8 bl_val;
+
+	/* Current source, initialized at probe time */
+	int curr_src;
+
+	/* Desired source */
+	int pending_src;
+
+	/* Variables used during switches */
+	bool switched;
+	ktime_t irq_time;
+	ktime_t load_time;
+
+	/* Current output type; true == mono, false == color */
+	bool mono;
+	/* This get set while controlling fb blank state from the driver */
+	bool ignore_fb_events;
+
+	struct gpio_desc *stat0_gpio;
+	struct gpio_desc *stat1_gpio;
+	struct gpio_desc *load_gpio;
+};
+
+static irqreturn_t hx8837_interrupt(int irq, void *id);
+
+/* I2C structures */
+
+static unsigned short normal_i2c[] = { 0x0d, I2C_CLIENT_END };
+
+static s32 hx8837_write(struct hx8837_priv *priv, u8 reg, u16 val)
+{
+	return i2c_smbus_write_word_data(priv->client, reg, val);
+}
+
+static s32 hx8837_read(struct hx8837_priv *priv, u8 reg)
+{
+	return i2c_smbus_read_word_data(priv->client, reg);
+}
+
+static void hx8837_hw_init(struct hx8837_priv *priv, int is_init)
+{
+	/* SDRAM setup/hold time */
+	hx8837_write(priv, 0x3a, 0xc040);
+	hx8837_write(priv, DCON_REG_MEM_OPT_A, 0x0000);  /* clear option bits */
+	hx8837_write(priv, DCON_REG_MEM_OPT_A,
+		   MEM_DLL_CLOCK_DELAY | MEM_POWER_DOWN);
+	hx8837_write(priv, DCON_REG_MEM_OPT_B, MEM_SOFT_RESET);
+
+	/* Colour swizzle, AA, no passthrough, backlight */
+	if (is_init) {
+		priv->disp_mode = MODE_PASSTHRU | MODE_BL_ENABLE |
+				MODE_CSWIZZLE | MODE_COL_AA;
+	}
+	hx8837_write(priv, DCON_REG_MODE, priv->disp_mode);
+
+	/* Set the scanline to interrupt on during resume */
+	hx8837_write(priv, DCON_REG_SCAN_INT, priv->resumeline);
+}
+
+static void hx8837_set_backlight(struct hx8837_priv *priv, u8 level)
+{
+	hx8837_write(priv, DCON_REG_BRIGHT, level);
+
+	/* Purposely turn off the backlight when we go to level 0 */
+	if (level == 0) {
+		priv->disp_mode &= ~MODE_BL_ENABLE;
+		hx8837_write(priv, DCON_REG_MODE, priv->disp_mode);
+	} else if (!(priv->disp_mode & MODE_BL_ENABLE)) {
+		priv->disp_mode |= MODE_BL_ENABLE;
+		hx8837_write(priv, DCON_REG_MODE, priv->disp_mode);
+	}
+}
+
+/* Set the output type to either color or mono */
+static int hx8837_set_mono_mode(struct hx8837_priv *priv, bool enable_mono)
+{
+	if (priv->mono == enable_mono)
+		return 0;
+
+	priv->mono = enable_mono;
+
+	if (enable_mono) {
+		priv->disp_mode &= ~(MODE_CSWIZZLE | MODE_COL_AA);
+		priv->disp_mode |= MODE_MONO_LUMA;
+	} else {
+		priv->disp_mode &= ~(MODE_MONO_LUMA);
+		priv->disp_mode |= MODE_CSWIZZLE | MODE_COL_AA;
+	}
+
+	hx8837_write(priv, DCON_REG_MODE, priv->disp_mode);
+	return 0;
+}
+
+/* the DCON seems to get confused if we change DCONLOAD too
+ * frequently -- i.e., approximately faster than frame time.
+ * normally we don't change it this fast, so in general we won't
+ * delay here.
+ */
+static void hx8837_load_holdoff(struct hx8837_priv *priv)
+{
+	ktime_t delta_t, now;
+
+	while (1) {
+		now = ktime_get();
+		delta_t = ktime_sub(now, priv->load_time);
+		if (ktime_to_ns(delta_t) > NSEC_PER_MSEC * 20)
+			break;
+		mdelay(4);
+	}
+}
+
+static bool hx8837_blank_fb(struct hx8837_priv *priv, bool blank)
+{
+	int err;
+
+	console_lock();
+	if (!lock_fb_info(priv->fbinfo)) {
+		console_unlock();
+		dev_err(&priv->client->dev, "unable to lock framebuffer\n");
+		return false;
+	}
+
+	priv->ignore_fb_events = true;
+	err = fb_blank(priv->fbinfo,
+		       blank ? FB_BLANK_POWERDOWN : FB_BLANK_UNBLANK);
+	priv->ignore_fb_events = false;
+	unlock_fb_info(priv->fbinfo);
+	console_unlock();
+
+	if (err) {
+		dev_err(&priv->client->dev, "couldn't %sblank framebuffer\n",
+			blank ? "" : "un");
+		return false;
+	}
+	return true;
+}
+
+/* Set the source of the display (CPU or DCON) */
+static void hx8837_source_switch(struct work_struct *work)
+{
+	struct hx8837_priv *priv = container_of(work, struct hx8837_priv,
+							switch_source);
+	struct device *dev = &priv->client->dev;
+	int source = priv->pending_src;
+
+	if (priv->curr_src == source)
+		return;
+
+	hx8837_load_holdoff(priv);
+
+	priv->switched = false;
+
+	switch (source) {
+	case DCON_SOURCE_CPU:
+		dev_info(dev, "%s to CPU\n", __func__);
+		/* Enable the scanline interrupt bit */
+		if (hx8837_write(priv, DCON_REG_MODE,
+			       priv->disp_mode | MODE_SCAN_INT))
+			dev_err(dev, "couldn't enable scanline interrupt!\n");
+		else
+			/* Wait up to one second for the scanline interrupt */
+			wait_event_timeout(priv->waitq, priv->switched, HZ);
+
+		if (!priv->switched)
+			dev_err(dev, "Timeout entering CPU mode; expect a screen glitch.\n");
+
+		/* Turn off the scanline interrupt */
+		if (hx8837_write(priv, DCON_REG_MODE, priv->disp_mode))
+			dev_err(dev, "couldn't disable scanline interrupt!\n");
+
+		/*
+		 * Ideally we'd like to disable interrupts here so that the
+		 * fb unblanking and DCON turn on happen at a known time value;
+		 * however, we can't do that right now with fb_blank
+		 * messing with semaphores.
+		 *
+		 * For now, we just hope..
+		 */
+		if (!hx8837_blank_fb(priv, false)) {
+			dev_err(dev, "Failed to enter CPU mode\n");
+			priv->pending_src = DCON_SOURCE_DCON;
+			return;
+		}
+
+		/* And turn off the DCON */
+		gpiod_set_value(priv->load_gpio, 1);
+		priv->load_time = ktime_get();
+
+		dev_info(dev, "The CPU has control\n");
+		break;
+	case DCON_SOURCE_DCON:
+		dev_info(dev, "%s to DCON\n", __func__);
+
+		/* Clear DCONLOAD - this implies that the DCON is in control */
+		gpiod_set_value(priv->load_gpio, 0);
+		priv->load_time = ktime_get();
+
+		wait_event_timeout(priv->waitq, priv->switched, HZ / 2);
+
+		if (!priv->switched) {
+			dev_err(dev, "Timeout entering DCON mode; expect a screen glitch.\n");
+		} else {
+			ktime_t delta_t;
+
+			/* sometimes the DCON doesn't follow its own rules,
+			 * and doesn't wait for two vsync pulses before
+			 * ack'ing the frame load with an IRQ.  the result
+			 * is that the display shows the *previously*
+			 * loaded frame.  we can detect this by looking at
+			 * the time between asserting DCONLOAD and the IRQ --
+			 * if it's less than 20msec, then the DCON couldn't
+			 * have seen two VSYNC pulses.  in that case we
+			 * deassert and reassert, and hope for the best.
+			 * see http://dev.laptop.org/ticket/9664
+			 */
+			delta_t = ktime_sub(priv->irq_time, priv->load_time);
+			if (priv->switched && ktime_to_ns(delta_t)
+			    < NSEC_PER_MSEC * 20) {
+				dev_err(dev, "missed loading, retrying\n");
+				gpiod_set_value(priv->load_gpio, 1);
+				mdelay(41);
+				gpiod_set_value(priv->load_gpio, 0);
+				priv->load_time = ktime_get();
+				mdelay(41);
+			}
+		}
+
+		hx8837_blank_fb(priv, true);
+		dev_info(dev, "The DCON has control\n");
+		break;
+	default:
+		WARN_ON(1);
+	}
+
+	priv->curr_src = source;
+}
+
+static void hx8837_set_source(struct hx8837_priv *priv, int arg)
+{
+	if (priv->pending_src == arg)
+		return;
+
+	priv->pending_src = arg;
+
+	if (priv->curr_src != arg)
+		schedule_work(&priv->switch_source);
+}
+
+static void hx8837_set_source_sync(struct hx8837_priv *priv, int arg)
+{
+	hx8837_set_source(priv, arg);
+	flush_scheduled_work();
+}
+
+static int hx8837_bl_update(struct backlight_device *dev)
+{
+	struct hx8837_priv *priv = bl_get_data(dev);
+	u8 level = dev->props.brightness & 0x0F;
+
+	priv->bl_val = level;
+
+	if (dev->props.power != FB_BLANK_UNBLANK)
+		level = 0;
+
+	if (dev->props.state & BL_CORE_FBBLANK)
+		level = 0;
+
+	hx8837_set_backlight(priv, level);
+
+	return 0;
+}
+
+static int hx8837_bl_get(struct backlight_device *dev)
+{
+	struct hx8837_priv *priv = bl_get_data(dev);
+
+	return priv->bl_val;
+}
+
+static const struct backlight_ops hx8837_bl_ops = {
+	.update_status = hx8837_bl_update,
+	.get_brightness = hx8837_bl_get,
+};
+
+static struct backlight_properties hx8837_bl_props = {
+	.max_brightness = 15,
+	.type = BACKLIGHT_RAW,
+	.power = FB_BLANK_UNBLANK,
+};
+
+static int hx8837_reboot_notify(struct notifier_block *nb, unsigned long foo,
+								void *bar)
+{
+	struct hx8837_priv *priv = container_of(nb, struct hx8837_priv,
+								reboot_nb);
+
+	/* Turn off the DCON. Entirely. */
+	hx8837_write(priv, DCON_REG_MODE, 0x39);
+	hx8837_write(priv, DCON_REG_MODE, 0x32);
+	return NOTIFY_DONE;
+}
+
+static int hx8837_panic_notify(struct notifier_block *nb, unsigned long e,
+								void *p)
+{
+	struct hx8837_priv *priv = container_of(nb, struct hx8837_priv,
+								panic_nb);
+
+	gpiod_set_value(priv->load_gpio, 1);
+	return NOTIFY_DONE;
+}
+
+static int hx8837_detect(struct i2c_client *client, struct i2c_board_info *info)
+{
+	strlcpy(info->type, "hx8837", I2C_NAME_SIZE);
+
+	return 0;
+}
+
+static ssize_t mode_show(struct device *dev, struct device_attribute *attr,
+								char *buf)
+{
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%4.4X\n", priv->disp_mode);
+}
+
+static ssize_t freeze_show(struct device *dev, struct device_attribute *attr,
+								char *buf)
+{
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", priv->curr_src == DCON_SOURCE_DCON ? 1 : 0);
+}
+
+static ssize_t monochrome_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", priv->mono);
+}
+
+static ssize_t resumeline_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", priv->resumeline);
+}
+
+static ssize_t monochrome_store(struct device *dev,
+			struct device_attribute *attr,
+			const char *buf, size_t count)
+{
+	unsigned long enable_mono;
+	int rc;
+
+	rc = kstrtoul(buf, 10, &enable_mono);
+	if (rc)
+		return rc;
+
+	hx8837_set_mono_mode(dev_get_drvdata(dev), enable_mono ? true : false);
+
+	return count;
+}
+
+static ssize_t freeze_store(struct device *dev, struct device_attribute *attr,
+						const char *buf, size_t count)
+{
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+	unsigned long output;
+	int ret;
+
+	ret = kstrtoul(buf, 10, &output);
+	if (ret)
+		return ret;
+
+	switch (output) {
+	case 0:
+		hx8837_set_source(priv, DCON_SOURCE_CPU);
+		break;
+	case 1:
+		hx8837_set_source_sync(priv, DCON_SOURCE_DCON);
+		break;
+	case 2:  /* normally unused */
+		hx8837_set_source(priv, DCON_SOURCE_DCON);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return count;
+}
+
+static ssize_t resumeline_store(struct device *dev,
+			struct device_attribute *attr,
+			const char *buf, size_t count)
+{
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+	unsigned short rl;
+	int rc;
+
+	rc = kstrtou16(buf, 10, &rl);
+	if (rc)
+		return rc;
+
+	priv->resumeline = rl;
+	hx8837_write(dev_get_drvdata(dev), DCON_REG_SCAN_INT, priv->resumeline);
+
+	return count;
+}
+
+
+static DEVICE_ATTR_RO(mode);
+static DEVICE_ATTR_RW(freeze);
+static DEVICE_ATTR_RW(monochrome);
+static DEVICE_ATTR_RW(resumeline);
+
+static struct attribute *hx8837_attrs[] = {
+	&dev_attr_mode.attr,
+	&dev_attr_freeze.attr,
+	&dev_attr_monochrome.attr,
+	&dev_attr_resumeline.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(hx8837);
+
+static int hx8837_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	struct hx8837_priv *priv;
+	u16 ver;
+	int rc;
+
+	if (num_registered_fb < 1)
+		return -EPROBE_DEFER;
+
+	priv = devm_kzalloc(&client->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->client = client;
+	init_waitqueue_head(&priv->waitq);
+	INIT_WORK(&priv->switch_source, hx8837_source_switch);
+	priv->reboot_nb.notifier_call = hx8837_reboot_notify;
+	priv->reboot_nb.priority = -1;
+	priv->panic_nb.notifier_call = hx8837_panic_notify;
+
+	/*
+	 * Perhaps we could add a phandle to the panel to a DT property so that
+	 * we'll be able to guess it from the vertical resolution instead of
+	 * hardwiring it?
+	 */
+	priv->resumeline = 898;
+
+	i2c_set_clientdata(client, priv);
+
+	priv->fbinfo = registered_fb[0];
+
+	priv->stat0_gpio = devm_gpiod_get_index(&client->dev, "stat", 0,
+								GPIOD_IN);
+	if (IS_ERR(priv->stat0_gpio)) {
+		dev_err(&client->dev, "failed to request STAT0 GPIO\n");
+		return PTR_ERR(priv->stat0_gpio);
+	};
+
+	priv->stat1_gpio = devm_gpiod_get_index(&client->dev, "stat", 1,
+								GPIOD_IN);
+	if (IS_ERR(priv->stat1_gpio)) {
+		dev_err(&client->dev, "failed to request STAT1 GPIO\n");
+		return PTR_ERR(priv->stat1_gpio);
+	};
+
+	priv->load_gpio = devm_gpiod_get(&client->dev, "load", GPIOD_IN);
+	if (IS_ERR(priv->load_gpio)) {
+		dev_err(&client->dev, "failed to request LOAD GPIO\n");
+		return PTR_ERR(priv->load_gpio);
+	};
+
+	ver = hx8837_read(priv, DCON_REG_ID);
+	if ((ver >> 8) != 0xDC) {
+		dev_err(&client->dev, "DCON ID not 0xDCxx: 0x%04x.\n", ver);
+		return -ENXIO;
+	}
+
+	dev_info(&client->dev, "Discovered DCON version %x\n", ver & 0xFF);
+
+	if (ver < 0xdc02) {
+		dev_err(&client->dev, "DCON v1 is unsupported, giving up.\n");
+		return -ENODEV;
+	}
+
+	/*
+	 * Determine the current state by reading the GPIO bit; earlier
+	 * stages of the boot process have established the state.
+	 */
+	priv->curr_src = gpiod_get_value(priv->load_gpio)
+			? DCON_SOURCE_CPU : DCON_SOURCE_DCON;
+	priv->pending_src = priv->curr_src;
+
+	/* Set the directions for the GPIO pins */
+	gpiod_direction_input(priv->stat0_gpio);
+	gpiod_direction_input(priv->stat1_gpio);
+	gpiod_direction_output(priv->load_gpio,
+		priv->curr_src == DCON_SOURCE_CPU);
+
+	/* Register the interrupt handler */
+	rc = devm_request_irq(&client->dev, client->irq, &hx8837_interrupt, 0,
+								"DCON", priv);
+	if (rc) {
+		dev_err(&client->dev, "IRQ request failed: %d\n", rc);
+		return rc;
+	}
+
+	hx8837_hw_init(priv, 1);
+
+	priv->bl_val = hx8837_read(priv, DCON_REG_BRIGHT) & 0x0F;
+
+	/* Add the backlight device for the DCON */
+	hx8837_bl_props.brightness = priv->bl_val;
+	priv->bl_dev = devm_backlight_device_register(&client->dev, "hx8837-bl",
+			&client->dev, priv, &hx8837_bl_ops, &hx8837_bl_props);
+	if (IS_ERR(priv->bl_dev)) {
+		dev_err(&client->dev, "cannot register backlight dev (%ld)\n",
+			PTR_ERR(priv->bl_dev));
+		priv->bl_dev = NULL;
+	}
+
+	rc = devm_device_add_groups(&client->dev, hx8837_groups);
+	if (rc) {
+		dev_err(&client->dev, "failed to register sysfs groups\n");
+		return rc;
+	}
+
+	devm_register_reboot_notifier(&client->dev, &priv->reboot_nb);
+	atomic_notifier_chain_register(&panic_notifier_list, &priv->panic_nb);
+
+	return 0;
+}
+
+static int hx8837_remove(struct i2c_client *client)
+{
+	struct hx8837_priv *priv = i2c_get_clientdata(client);
+
+	atomic_notifier_chain_unregister(&panic_notifier_list,
+					&priv->panic_nb);
+
+	cancel_work_sync(&priv->switch_source);
+
+	return 0;
+}
+
+static irqreturn_t hx8837_interrupt(int irq, void *id)
+{
+	struct hx8837_priv *priv = id;
+	struct device *dev = &priv->client->dev;
+	u8 status;
+
+	status = gpiod_get_value(priv->stat0_gpio);
+	status |= gpiod_get_value(priv->stat1_gpio) << 1;
+
+
+	switch (status & 3) {
+	case 3:
+		dev_dbg(dev, "DCONLOAD_MISSED interrupt\n");
+		break;
+
+	case 2:	/* switch to DCON mode */
+	case 1: /* switch to CPU mode */
+		priv->switched = true;
+		priv->irq_time = ktime_get();
+		wake_up(&priv->waitq);
+		break;
+
+	case 0:
+		/* workaround resume case:  the DCON (on 1.5) doesn't
+		 * ever assert status 0x01 when switching to CPU mode
+		 * during resume.  this is because DCONLOAD is de-asserted
+		 * _immediately_ upon exiting S3, so the actual release
+		 * of the DCON happened long before this point.
+		 * see http://dev.laptop.org/ticket/9869
+		 */
+		if (priv->curr_src != priv->pending_src && !priv->switched) {
+			priv->switched = true;
+			priv->irq_time = ktime_get();
+			wake_up(&priv->waitq);
+			dev_dbg(dev, "switching w/ status 0/0\n");
+		} else {
+			dev_dbg(dev, "scanline interrupt w/CPU\n");
+		}
+	}
+
+	return IRQ_HANDLED;
+}
+
+#ifdef CONFIG_PM
+static int hx8837_suspend(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct hx8837_priv *priv = i2c_get_clientdata(client);
+
+	hx8837_set_source_sync(priv, DCON_SOURCE_DCON);
+
+	return 0;
+}
+
+static int hx8837_resume(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct hx8837_priv *priv = i2c_get_clientdata(client);
+
+	hx8837_set_source(priv, DCON_SOURCE_CPU);
+
+	return 0;
+}
+#endif /* CONFIG_PM */
+
+static SIMPLE_DEV_PM_OPS(hx8837_pm_ops, hx8837_suspend, hx8837_resume);
+
+static const struct of_device_id hx8837_dt_ids[] = {
+	{ .compatible = "himax,hx8837", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, hx8837_dt_ids);
+
+static const struct i2c_device_id hx8837_i2c_ids[] = {
+	{ .name = "hx8837", },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, hx8837_i2c_ids);
+
+static struct i2c_driver hx8837_driver = {
+	.driver = {
+		.name = "hx8837",
+		.pm = &hx8837_pm_ops,
+		.of_match_table = hx8837_dt_ids,
+	},
+	.class = I2C_CLASS_DDC | I2C_CLASS_HWMON,
+	.id_table = hx8837_i2c_ids,
+	.probe = hx8837_probe,
+	.remove = hx8837_remove,
+	.detect = hx8837_detect,
+	.address_list = normal_i2c,
+};
+
+module_i2c_driver(hx8837_driver);
+
+MODULE_DESCRIPTION("HX8837 Display Controller Driver");
+MODULE_LICENSE("GPL v2");
-- 
2.19.1

Re: [PATCH 2/2] misc: hx8837: add a HiMax HX8837 display controller driver

[Greg Kroah-Hartman]

On Mon, Nov 12, 2018 at 03:39:29AM +0100, Lubomir Rintel wrote:
> HiMax HX8837 is a display controller used on OLPC platforms. It controls
> backlight and is able to capture and freeze a frame when the LCD controller
> (and the rest of the plaform) is powered off.
> 
> This driver is based on the same code as drivers/staging/olpc_dcon.
> I modernized it to use managed GPIO, device-tree bindings, sysfs attribtue
> groups, essentially fixing the staging driver's TODO.

You are creating custom sysfs files, with no Documentation/ABI/ update
for us to know what those files are or how they are used :(

Why do you need custom sysfs files in the first place?  Isn't there
already an api for this type of device in the kernel?

thanks,

greg k-h

Re: [PATCH 2/2] misc: hx8837: add a HiMax HX8837 display controller driver

[Lubomir Rintel]

On Tue, 2018-11-27 at 08:41 +0100, Greg Kroah-Hartman wrote:
> On Mon, Nov 12, 2018 at 03:39:29AM +0100, Lubomir Rintel wrote:
> > HiMax HX8837 is a display controller used on OLPC platforms. It controls
> > backlight and is able to capture and freeze a frame when the LCD controller
> > (and the rest of the plaform) is powered off.
> > 
> > This driver is based on the same code as drivers/staging/olpc_dcon.
> > I modernized it to use managed GPIO, device-tree bindings, sysfs attribtue
> > groups, essentially fixing the staging driver's TODO.
> 
> You are creating custom sysfs files, with no Documentation/ABI/ update
> for us to know what those files are or how they are used :(
> 
> Why do you need custom sysfs files in the first place?  Isn't there
> already an api for this type of device in the kernel?

I am actually not sure. I certainly didn't find anything similar.

I've later discovered that this should perhaps be a DRM encoder driver,
because it sits between the LCDC and the panel; I'm submitting an
updated RFC version to the dri list.

Perhaps the color swizzling and frame freezing functionality that's
exposed via sysfs in this version could be exposed as a DRI property
instead.

> 
> thanks,
> 
> greg k-h

Lubo

[PATCH 1/2] dt-bindings: himax,hx8837: add HiMax HX8837 bindings

[Lubomir Rintel]

HiMax HX8837 is a display controller used on OLPC platforms.
It controlls backlight and is able to capture and freeze a frame when
the LCD controller (and the rest of the plaform) is powered off.

What is missing here is the description of connections to the LCD
controller and the panel. Maybe it would be a good idea to plug in it
betweend the two in a manner described in
<Documentation/devicetree/bindings/graph.txt>.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
---
Changes since v1:
- s/load-gpio/load-gpios/
- Use interrupt bindings instead of gpio for the IRQ

 .../devicetree/bindings/misc/himax,hx8837.txt  | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/misc/himax,hx8837.txt

diff --git a/Documentation/devicetree/bindings/misc/himax,hx8837.txt b/Documentation/devicetree/bindings/misc/himax,hx8837.txt
new file mode 100644
index 000000000000..d0822c679ae8
--- /dev/null
+++ b/Documentation/devicetree/bindings/misc/himax,hx8837.txt
@@ -0,0 +1,18 @@
+HX8837 Display Controller
+
+Required properties:
+- compatible: Should be "himax,hx8837".
+- reg: I2C address, must be 0x0d
+- stat-gpios: gpio specifier of DCON_STAT0 and DCON_STAT1 pins (active high)
+- load-gpios: gpio specifier of DCON_LOAD pin (active high)
+- interrupt: interrupt specifier of DCON_IRQ pin (edge falling)
+
+Example:
+	dcon@d {
+		compatible = "himax,hx8837";
+		reg = <0x0d>;
+		stat-gpios = <&gpio 100 GPIO_ACTIVE_HIGH
+			      &gpio 101 GPIO_ACTIVE_HIGH>;
+		load-gpios = <&gpio 142 GPIO_ACTIVE_HIGH>;
+		interrupts = <&gpio 124 IRQ_TYPE_EDGE_FALLING>;
+	};
-- 
2.19.0

[PATCH 2/2] misc: hx8837: add a HiMax HX8837 display controller driver

[Lubomir Rintel]

HiMax HX8837 is a display controller used on OLPC platforms. It controlls
backlight and is able to capture and freeze a frame when the LCD controller
(and the rest of the plaform) is powered off.

This driver is based on the same code as drivers/staging/olpc_dcon.
I modernized it to use managed GPIO, device-tree bindings, sysfs attribtue
groups, essentially fixing the staging driver's TODO.

Why I am not removing the staging driver now is because I've hobbled off
some functionality too (with an intent to bring add it back eventually):

* I've removed parts that talk directly to the OLPC EC to turn off/on the
  power. A separate patch will make the EC expose a regulator interface
  that should be used instead.

* Some work is likely needed to make XO 1 and XO 1.5 work. Both platforms
  are DT-based and could use the same bindings, but I haven't checked
  whether the cs5535 and vx855 GPIO drivers are good enough.

What is there is the backlight control and the sysfs attributes to control
the freeze/unfreeze..

I've also renamed the driver to use the actual chip name instead of the
original name that I found too generic. This way the staging driver can be
used on XO 1 and XO 1.5 for the time being, while my XO 1.75 can utilize
this one.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
---
Changes since v1:
- Use interrupt bindings instead of gpio for the IRQ
- Update the statement on XO 1/1.5 support in the commit message

 drivers/misc/Kconfig  |  16 +
 drivers/misc/Makefile |   1 +
 drivers/misc/hx8837.c | 741 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 758 insertions(+)
 create mode 100644 drivers/misc/hx8837.c

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 3726eacdf65d..3eb6df0ea0a4 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -513,6 +513,22 @@ config MISC_RTSX
 	tristate
 	default MISC_RTSX_PCI || MISC_RTSX_USB
 
+config HX8837_DCON
+        tristate "HiMax HX8837 Display Controller on OLPC"
+        depends on I2C
+        depends on BACKLIGHT_LCD_SUPPORT
+        select BACKLIGHT_CLASS_DEVICE
+        help
+          In order to support very low power operation, the OLPC XO laptop uses a
+          secondary Display Controller, or DCON.  This secondary controller
+          is present in the video pipeline between the primary display
+          controller (integrate into the processor or chipset) and the LCD
+          panel.  It allows the main processor/display controller to be
+          completely powered off while still retaining an image on the display.
+          This controller is only available on OLPC platforms.
+
+          Unless you have an OLPC XO laptop, you will want to say N.
+
 source "drivers/misc/c2port/Kconfig"
 source "drivers/misc/eeprom/Kconfig"
 source "drivers/misc/cb710/Kconfig"
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index af22bbc3d00c..33689ae496b4 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -58,3 +58,4 @@ obj-$(CONFIG_ASPEED_LPC_SNOOP)	+= aspeed-lpc-snoop.o
 obj-$(CONFIG_PCI_ENDPOINT_TEST)	+= pci_endpoint_test.o
 obj-$(CONFIG_OCXL)		+= ocxl/
 obj-$(CONFIG_MISC_RTSX)		+= cardreader/
+obj-$(CONFIG_HX8837_DCON)	+= hx8837.o
diff --git a/drivers/misc/hx8837.c b/drivers/misc/hx8837.c
new file mode 100644
index 000000000000..cff02ed54de3
--- /dev/null
+++ b/drivers/misc/hx8837.c
@@ -0,0 +1,741 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Mainly by David Woodhouse, somewhat modified by Jordan Crouse.
+ * Modernized to use managed GPIO, device-tree, etc. by Lubomir Rintel.
+ *
+ * Copyright (C) 2006-2007  Red Hat, Inc.
+ * Copyright (C) 2006-2007  Advanced Micro Devices, Inc.
+ * Copyright (C) 2009       VIA Technology, Inc.
+ * Copyright (C) 2010-2011  Andres Salomon <dilinger@queued.net>
+ * Copyright (C) 2018       Lubomir Rintel <lkundrak@v3.sk>
+ */
+
+#include <linux/module.h>
+#include <linux/backlight.h>
+#include <linux/console.h>
+#include <linux/ctype.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/fb.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/notifier.h>
+#include <linux/reboot.h>
+
+/* DCON registers */
+
+#define DCON_REG_ID		 0
+#define DCON_REG_MODE		 1
+
+#define MODE_PASSTHRU		BIT(0)
+#define MODE_SLEEP		BIT(1)
+#define MODE_SLEEP_AUTO		BIT(2)
+#define MODE_BL_ENABLE		BIT(3)
+#define MODE_BLANK		BIT(4)
+#define MODE_CSWIZZLE		BIT(5)
+#define MODE_COL_AA		BIT(6)
+#define MODE_MONO_LUMA		BIT(7)
+#define MODE_SCAN_INT		BIT(8)
+#define MODE_CLOCKDIV		BIT(9)
+#define MODE_DEBUG		BIT(14)
+#define MODE_SELFTEST		BIT(15)
+
+#define DCON_REG_HRES		0x2
+#define DCON_REG_HTOTAL		0x3
+#define DCON_REG_HSYNC_WIDTH	0x4
+#define DCON_REG_VRES		0x5
+#define DCON_REG_VTOTAL		0x6
+#define DCON_REG_VSYNC_WIDTH	0x7
+#define DCON_REG_TIMEOUT	0x8
+#define DCON_REG_SCAN_INT	0x9
+#define DCON_REG_BRIGHT		0xa
+#define DCON_REG_MEM_OPT_A	0x41
+#define DCON_REG_MEM_OPT_B	0x42
+
+/* Load Delay Locked Loop (DLL) settings for clock delay */
+#define MEM_DLL_CLOCK_DELAY	BIT(0)
+/* Memory controller power down function */
+#define MEM_POWER_DOWN		BIT(8)
+/* Memory controller software reset */
+#define MEM_SOFT_RESET		BIT(0)
+
+/* Status values */
+
+#define DCONSTAT_SCANINT	0
+#define DCONSTAT_SCANINT_DCON	1
+#define DCONSTAT_DISPLAYLOAD	2
+#define DCONSTAT_MISSED		3
+
+/* Source values */
+
+#define DCON_SOURCE_DCON        0
+#define DCON_SOURCE_CPU         1
+
+struct hx8837_priv {
+	struct i2c_client *client;
+	struct fb_info *fbinfo;
+	struct backlight_device *bl_dev;
+
+	wait_queue_head_t waitq;
+	struct work_struct switch_source;
+	struct notifier_block reboot_nb;
+	struct notifier_block panic_nb;
+
+	/* Scanline to interrupt on during resume */
+	ushort resumeline;
+
+	/* Shadow register for the DCON_REG_MODE register */
+	u8 disp_mode;
+
+	/* The current backlight value - this saves us some smbus traffic */
+	u8 bl_val;
+
+	/* Current source, initialized at probe time */
+	int curr_src;
+
+	/* Desired source */
+	int pending_src;
+
+	/* Variables used during switches */
+	bool switched;
+	ktime_t irq_time;
+	ktime_t load_time;
+
+	/* Current output type; true == mono, false == color */
+	bool mono;
+	/* This get set while controlling fb blank state from the driver */
+	bool ignore_fb_events;
+
+	struct gpio_desc *stat0_gpio;
+	struct gpio_desc *stat1_gpio;
+	struct gpio_desc *load_gpio;
+};
+
+static irqreturn_t hx8837_interrupt(int irq, void *id);
+
+/* I2C structures */
+
+static unsigned short normal_i2c[] = { 0x0d, I2C_CLIENT_END };
+
+static s32 hx8837_write(struct hx8837_priv *priv, u8 reg, u16 val)
+{
+	return i2c_smbus_write_word_data(priv->client, reg, val);
+}
+
+static s32 hx8837_read(struct hx8837_priv *priv, u8 reg)
+{
+	return i2c_smbus_read_word_data(priv->client, reg);
+}
+
+static void hx8837_hw_init(struct hx8837_priv *priv, int is_init)
+{
+	/* SDRAM setup/hold time */
+	hx8837_write(priv, 0x3a, 0xc040);
+	hx8837_write(priv, DCON_REG_MEM_OPT_A, 0x0000);  /* clear option bits */
+	hx8837_write(priv, DCON_REG_MEM_OPT_A,
+		   MEM_DLL_CLOCK_DELAY | MEM_POWER_DOWN);
+	hx8837_write(priv, DCON_REG_MEM_OPT_B, MEM_SOFT_RESET);
+
+	/* Colour swizzle, AA, no passthrough, backlight */
+	if (is_init) {
+		priv->disp_mode = MODE_PASSTHRU | MODE_BL_ENABLE |
+				MODE_CSWIZZLE | MODE_COL_AA;
+	}
+	hx8837_write(priv, DCON_REG_MODE, priv->disp_mode);
+
+	/* Set the scanline to interrupt on during resume */
+	hx8837_write(priv, DCON_REG_SCAN_INT, priv->resumeline);
+}
+
+static void hx8837_set_backlight(struct hx8837_priv *priv, u8 level)
+{
+	hx8837_write(priv, DCON_REG_BRIGHT, level);
+
+	/* Purposely turn off the backlight when we go to level 0 */
+	if (level == 0) {
+		priv->disp_mode &= ~MODE_BL_ENABLE;
+		hx8837_write(priv, DCON_REG_MODE, priv->disp_mode);
+	} else if (!(priv->disp_mode & MODE_BL_ENABLE)) {
+		priv->disp_mode |= MODE_BL_ENABLE;
+		hx8837_write(priv, DCON_REG_MODE, priv->disp_mode);
+	}
+}
+
+/* Set the output type to either color or mono */
+static int hx8837_set_mono_mode(struct hx8837_priv *priv, bool enable_mono)
+{
+	if (priv->mono == enable_mono)
+		return 0;
+
+	priv->mono = enable_mono;
+
+	if (enable_mono) {
+		priv->disp_mode &= ~(MODE_CSWIZZLE | MODE_COL_AA);
+		priv->disp_mode |= MODE_MONO_LUMA;
+	} else {
+		priv->disp_mode &= ~(MODE_MONO_LUMA);
+		priv->disp_mode |= MODE_CSWIZZLE | MODE_COL_AA;
+	}
+
+	hx8837_write(priv, DCON_REG_MODE, priv->disp_mode);
+	return 0;
+}
+
+/* the DCON seems to get confused if we change DCONLOAD too
+ * frequently -- i.e., approximately faster than frame time.
+ * normally we don't change it this fast, so in general we won't
+ * delay here.
+ */
+static void hx8837_load_holdoff(struct hx8837_priv *priv)
+{
+	ktime_t delta_t, now;
+
+	while (1) {
+		now = ktime_get();
+		delta_t = ktime_sub(now, priv->load_time);
+		if (ktime_to_ns(delta_t) > NSEC_PER_MSEC * 20)
+			break;
+		mdelay(4);
+	}
+}
+
+static bool hx8837_blank_fb(struct hx8837_priv *priv, bool blank)
+{
+	int err;
+
+	console_lock();
+	if (!lock_fb_info(priv->fbinfo)) {
+		console_unlock();
+		dev_err(&priv->client->dev, "unable to lock framebuffer\n");
+		return false;
+	}
+
+	priv->ignore_fb_events = true;
+	err = fb_blank(priv->fbinfo,
+		       blank ? FB_BLANK_POWERDOWN : FB_BLANK_UNBLANK);
+	priv->ignore_fb_events = false;
+	unlock_fb_info(priv->fbinfo);
+	console_unlock();
+
+	if (err) {
+		dev_err(&priv->client->dev, "couldn't %sblank framebuffer\n",
+			blank ? "" : "un");
+		return false;
+	}
+	return true;
+}
+
+/* Set the source of the display (CPU or DCON) */
+static void hx8837_source_switch(struct work_struct *work)
+{
+	struct hx8837_priv *priv = container_of(work, struct hx8837_priv,
+							switch_source);
+	struct device *dev = &priv->client->dev;
+	int source = priv->pending_src;
+
+	if (priv->curr_src == source)
+		return;
+
+	hx8837_load_holdoff(priv);
+
+	priv->switched = false;
+
+	switch (source) {
+	case DCON_SOURCE_CPU:
+		dev_info(dev, "%s to CPU\n", __func__);
+		/* Enable the scanline interrupt bit */
+		if (hx8837_write(priv, DCON_REG_MODE,
+			       priv->disp_mode | MODE_SCAN_INT))
+			dev_err(dev, "couldn't enable scanline interrupt!\n");
+		else
+			/* Wait up to one second for the scanline interrupt */
+			wait_event_timeout(priv->waitq, priv->switched, HZ);
+
+		if (!priv->switched)
+			dev_err(dev, "Timeout entering CPU mode; expect a screen glitch.\n");
+
+		/* Turn off the scanline interrupt */
+		if (hx8837_write(priv, DCON_REG_MODE, priv->disp_mode))
+			dev_err(dev, "couldn't disable scanline interrupt!\n");
+
+		/*
+		 * Ideally we'd like to disable interrupts here so that the
+		 * fb unblanking and DCON turn on happen at a known time value;
+		 * however, we can't do that right now with fb_blank
+		 * messing with semaphores.
+		 *
+		 * For now, we just hope..
+		 */
+		if (!hx8837_blank_fb(priv, false)) {
+			dev_err(dev, "Failed to enter CPU mode\n");
+			priv->pending_src = DCON_SOURCE_DCON;
+			return;
+		}
+
+		/* And turn off the DCON */
+		gpiod_set_value(priv->load_gpio, 1);
+		priv->load_time = ktime_get();
+
+		dev_info(dev, "The CPU has control\n");
+		break;
+	case DCON_SOURCE_DCON:
+		dev_info(dev, "%s to DCON\n", __func__);
+
+		/* Clear DCONLOAD - this implies that the DCON is in control */
+		gpiod_set_value(priv->load_gpio, 0);
+		priv->load_time = ktime_get();
+
+		wait_event_timeout(priv->waitq, priv->switched, HZ / 2);
+
+		if (!priv->switched) {
+			dev_err(dev, "Timeout entering DCON mode; expect a screen glitch.\n");
+		} else {
+			ktime_t delta_t;
+
+			/* sometimes the DCON doesn't follow its own rules,
+			 * and doesn't wait for two vsync pulses before
+			 * ack'ing the frame load with an IRQ.  the result
+			 * is that the display shows the *previously*
+			 * loaded frame.  we can detect this by looking at
+			 * the time between asserting DCONLOAD and the IRQ --
+			 * if it's less than 20msec, then the DCON couldn't
+			 * have seen two VSYNC pulses.  in that case we
+			 * deassert and reassert, and hope for the best.
+			 * see http://dev.laptop.org/ticket/9664
+			 */
+			delta_t = ktime_sub(priv->irq_time, priv->load_time);
+			if (priv->switched && ktime_to_ns(delta_t)
+			    < NSEC_PER_MSEC * 20) {
+				dev_err(dev, "missed loading, retrying\n");
+				gpiod_set_value(priv->load_gpio, 1);
+				mdelay(41);
+				gpiod_set_value(priv->load_gpio, 0);
+				priv->load_time = ktime_get();
+				mdelay(41);
+			}
+		}
+
+		hx8837_blank_fb(priv, true);
+		dev_info(dev, "The DCON has control\n");
+		break;
+	default:
+		WARN_ON(1);
+	}
+
+	priv->curr_src = source;
+}
+
+static void hx8837_set_source(struct hx8837_priv *priv, int arg)
+{
+	if (priv->pending_src == arg)
+		return;
+
+	priv->pending_src = arg;
+
+	if (priv->curr_src != arg)
+		schedule_work(&priv->switch_source);
+}
+
+static void hx8837_set_source_sync(struct hx8837_priv *priv, int arg)
+{
+	hx8837_set_source(priv, arg);
+	flush_scheduled_work();
+}
+
+static int hx8837_bl_update(struct backlight_device *dev)
+{
+	struct hx8837_priv *priv = bl_get_data(dev);
+	u8 level = dev->props.brightness & 0x0F;
+
+	priv->bl_val = level;
+
+	if (dev->props.power != FB_BLANK_UNBLANK)
+		level = 0;
+
+	if (dev->props.state & BL_CORE_FBBLANK)
+		level = 0;
+
+	hx8837_set_backlight(priv, level);
+
+	return 0;
+}
+
+static int hx8837_bl_get(struct backlight_device *dev)
+{
+	struct hx8837_priv *priv = bl_get_data(dev);
+
+	return priv->bl_val;
+}
+
+static const struct backlight_ops hx8837_bl_ops = {
+	.update_status = hx8837_bl_update,
+	.get_brightness = hx8837_bl_get,
+};
+
+static struct backlight_properties hx8837_bl_props = {
+	.max_brightness = 15,
+	.type = BACKLIGHT_RAW,
+	.power = FB_BLANK_UNBLANK,
+};
+
+static int hx8837_reboot_notify(struct notifier_block *nb, unsigned long foo,
+								void *bar)
+{
+	struct hx8837_priv *priv = container_of(nb, struct hx8837_priv,
+								reboot_nb);
+
+	/* Turn off the DCON. Entirely. */
+	hx8837_write(priv, DCON_REG_MODE, 0x39);
+	hx8837_write(priv, DCON_REG_MODE, 0x32);
+	return NOTIFY_DONE;
+}
+
+static int hx8837_panic_notify(struct notifier_block *nb, unsigned long e,
+								void *p)
+{
+	struct hx8837_priv *priv = container_of(nb, struct hx8837_priv,
+								panic_nb);
+
+	gpiod_set_value(priv->load_gpio, 1);
+	return NOTIFY_DONE;
+}
+
+static int hx8837_detect(struct i2c_client *client, struct i2c_board_info *info)
+{
+	strlcpy(info->type, "hx8837", I2C_NAME_SIZE);
+
+	return 0;
+}
+
+static ssize_t mode_show(struct device *dev, struct device_attribute *attr,
+								char *buf)
+{
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%4.4X\n", priv->disp_mode);
+}
+
+static ssize_t freeze_show(struct device *dev, struct device_attribute *attr,
+								char *buf)
+{
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", priv->curr_src == DCON_SOURCE_DCON ? 1 : 0);
+}
+
+static ssize_t monochrome_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", priv->mono);
+}
+
+static ssize_t resumeline_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", priv->resumeline);
+}
+
+static ssize_t monochrome_store(struct device *dev,
+			struct device_attribute *attr,
+			const char *buf, size_t count)
+{
+	unsigned long enable_mono;
+	int rc;
+
+	rc = kstrtoul(buf, 10, &enable_mono);
+	if (rc)
+		return rc;
+
+	hx8837_set_mono_mode(dev_get_drvdata(dev), enable_mono ? true : false);
+
+	return count;
+}
+
+static ssize_t freeze_store(struct device *dev, struct device_attribute *attr,
+						const char *buf, size_t count)
+{
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+	unsigned long output;
+	int ret;
+
+	ret = kstrtoul(buf, 10, &output);
+	if (ret)
+		return ret;
+
+	switch (output) {
+	case 0:
+		hx8837_set_source(priv, DCON_SOURCE_CPU);
+		break;
+	case 1:
+		hx8837_set_source_sync(priv, DCON_SOURCE_DCON);
+		break;
+	case 2:  /* normally unused */
+		hx8837_set_source(priv, DCON_SOURCE_DCON);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return count;
+}
+
+static ssize_t resumeline_store(struct device *dev,
+			struct device_attribute *attr,
+			const char *buf, size_t count)
+{
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+	unsigned short rl;
+	int rc;
+
+	rc = kstrtou16(buf, 10, &rl);
+	if (rc)
+		return rc;
+
+	priv->resumeline = rl;
+	hx8837_write(dev_get_drvdata(dev), DCON_REG_SCAN_INT, priv->resumeline);
+
+	return count;
+}
+
+
+static DEVICE_ATTR_RO(mode);
+static DEVICE_ATTR_RW(freeze);
+static DEVICE_ATTR_RW(monochrome);
+static DEVICE_ATTR_RW(resumeline);
+
+static struct attribute *hx8837_attrs[] = {
+	&dev_attr_mode.attr,
+	&dev_attr_freeze.attr,
+	&dev_attr_monochrome.attr,
+	&dev_attr_resumeline.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(hx8837);
+
+static int hx8837_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	struct hx8837_priv *priv;
+	u16 ver;
+	int rc;
+
+	if (num_registered_fb < 1)
+		return -EPROBE_DEFER;
+
+	priv = devm_kzalloc(&client->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->client = client;
+	init_waitqueue_head(&priv->waitq);
+	INIT_WORK(&priv->switch_source, hx8837_source_switch);
+	priv->reboot_nb.notifier_call = hx8837_reboot_notify;
+	priv->reboot_nb.priority = -1;
+	priv->panic_nb.notifier_call = hx8837_panic_notify;
+
+	/*
+	 * Perhaps we could add a phandle to the panel to a DT property so that
+	 * we'll be able to guess it from the vertical resolution instead of
+	 * hardwiring it?
+	 */
+	priv->resumeline = 898;
+
+	i2c_set_clientdata(client, priv);
+
+	priv->fbinfo = registered_fb[0];
+
+	priv->stat0_gpio = devm_gpiod_get_index(&client->dev, "stat", 0,
+								GPIOD_IN);
+	if (IS_ERR(priv->stat0_gpio)) {
+		dev_err(&client->dev, "failed to request STAT0 GPIO\n");
+		return PTR_ERR(priv->stat0_gpio);
+	};
+
+	priv->stat1_gpio = devm_gpiod_get_index(&client->dev, "stat", 1,
+								GPIOD_IN);
+	if (IS_ERR(priv->stat1_gpio)) {
+		dev_err(&client->dev, "failed to request STAT1 GPIO\n");
+		return PTR_ERR(priv->stat1_gpio);
+	};
+
+	priv->load_gpio = devm_gpiod_get(&client->dev, "load", GPIOD_IN);
+	if (IS_ERR(priv->load_gpio)) {
+		dev_err(&client->dev, "failed to request LOAD GPIO\n");
+		return PTR_ERR(priv->load_gpio);
+	};
+
+	ver = hx8837_read(priv, DCON_REG_ID);
+	if ((ver >> 8) != 0xDC) {
+		dev_err(&client->dev, "DCON ID not 0xDCxx: 0x%04x.\n", ver);
+		return -ENXIO;
+	}
+
+	dev_info(&client->dev, "Discovered DCON version %x\n", ver & 0xFF);
+
+	if (ver < 0xdc02) {
+		dev_err(&client->dev, "DCON v1 is unsupported, giving up.\n");
+		return -ENODEV;
+	}
+
+	/*
+	 * Determine the current state by reading the GPIO bit; earlier
+	 * stages of the boot process have established the state.
+	 */
+	priv->curr_src = gpiod_get_value(priv->load_gpio)
+			? DCON_SOURCE_CPU : DCON_SOURCE_DCON;
+	priv->pending_src = priv->curr_src;
+
+	/* Set the directions for the GPIO pins */
+	gpiod_direction_input(priv->stat0_gpio);
+	gpiod_direction_input(priv->stat1_gpio);
+	gpiod_direction_output(priv->load_gpio,
+		priv->curr_src == DCON_SOURCE_CPU);
+
+	/* Register the interrupt handler */
+	rc = devm_request_irq(&client->dev, client->irq, &hx8837_interrupt, 0,
+								"DCON", priv);
+	if (rc) {
+		dev_err(&client->dev, "IRQ request failed: %d\n", rc);
+		return rc;
+	}
+
+	hx8837_hw_init(priv, 1);
+
+	priv->bl_val = hx8837_read(priv, DCON_REG_BRIGHT) & 0x0F;
+
+	/* Add the backlight device for the DCON */
+	hx8837_bl_props.brightness = priv->bl_val;
+	priv->bl_dev = devm_backlight_device_register(&client->dev, "hx8837-bl",
+			&client->dev, priv, &hx8837_bl_ops, &hx8837_bl_props);
+	if (IS_ERR(priv->bl_dev)) {
+		dev_err(&client->dev, "cannot register backlight dev (%ld)\n",
+			PTR_ERR(priv->bl_dev));
+		priv->bl_dev = NULL;
+	}
+
+	rc = devm_device_add_groups(&client->dev, hx8837_groups);
+	if (rc) {
+		dev_err(&client->dev, "failed to register sysfs groups\n");
+		return rc;
+	}
+
+	devm_register_reboot_notifier(&client->dev, &priv->reboot_nb);
+	atomic_notifier_chain_register(&panic_notifier_list, &priv->panic_nb);
+
+	return 0;
+}
+
+static int hx8837_remove(struct i2c_client *client)
+{
+	struct hx8837_priv *priv = i2c_get_clientdata(client);
+
+	atomic_notifier_chain_unregister(&panic_notifier_list,
+					&priv->panic_nb);
+
+	cancel_work_sync(&priv->switch_source);
+
+	return 0;
+}
+
+static irqreturn_t hx8837_interrupt(int irq, void *id)
+{
+	struct hx8837_priv *priv = id;
+	struct device *dev = &priv->client->dev;
+	u8 status;
+
+	status = gpiod_get_value(priv->stat0_gpio);
+	status |= gpiod_get_value(priv->stat1_gpio) << 1;
+
+
+	switch (status & 3) {
+	case 3:
+		dev_dbg(dev, "DCONLOAD_MISSED interrupt\n");
+		break;
+
+	case 2:	/* switch to DCON mode */
+	case 1: /* switch to CPU mode */
+		priv->switched = true;
+		priv->irq_time = ktime_get();
+		wake_up(&priv->waitq);
+		break;
+
+	case 0:
+		/* workaround resume case:  the DCON (on 1.5) doesn't
+		 * ever assert status 0x01 when switching to CPU mode
+		 * during resume.  this is because DCONLOAD is de-asserted
+		 * _immediately_ upon exiting S3, so the actual release
+		 * of the DCON happened long before this point.
+		 * see http://dev.laptop.org/ticket/9869
+		 */
+		if (priv->curr_src != priv->pending_src && !priv->switched) {
+			priv->switched = true;
+			priv->irq_time = ktime_get();
+			wake_up(&priv->waitq);
+			dev_dbg(dev, "switching w/ status 0/0\n");
+		} else {
+			dev_dbg(dev, "scanline interrupt w/CPU\n");
+		}
+	}
+
+	return IRQ_HANDLED;
+}
+
+#ifdef CONFIG_PM
+static int hx8837_suspend(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct hx8837_priv *priv = i2c_get_clientdata(client);
+
+	hx8837_set_source_sync(priv, DCON_SOURCE_DCON);
+
+	return 0;
+}
+
+static int hx8837_resume(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct hx8837_priv *priv = i2c_get_clientdata(client);
+
+	hx8837_set_source(priv, DCON_SOURCE_CPU);
+
+	return 0;
+}
+#endif /* CONFIG_PM */
+
+static SIMPLE_DEV_PM_OPS(hx8837_pm_ops, hx8837_suspend, hx8837_resume);
+
+static const struct of_device_id hx8837_dt_ids[] = {
+	{ .compatible = "himax,hx8837", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, hx8837_dt_ids);
+
+static const struct i2c_device_id hx8837_i2c_ids[] = {
+	{ .name = "hx8837", },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, hx8837_i2c_ids);
+
+static struct i2c_driver hx8837_driver = {
+	.driver = {
+		.name = "hx8837",
+		.pm = &hx8837_pm_ops,
+		.of_match_table = hx8837_dt_ids,
+	},
+	.class = I2C_CLASS_DDC | I2C_CLASS_HWMON,
+	.id_table = hx8837_i2c_ids,
+	.probe = hx8837_probe,
+	.remove = hx8837_remove,
+	.detect = hx8837_detect,
+	.address_list = normal_i2c,
+};
+
+module_i2c_driver(hx8837_driver);
+
+MODULE_DESCRIPTION("HX8837 Display Controller Driver");
+MODULE_LICENSE("GPL v2");
-- 
2.19.0

Re: [PATCH 2/2] misc: hx8837: add a HiMax HX8837 display controller driver

[Rob Herring]

On Mon,  8 Oct 2018 22:23:21 +0200, Lubomir Rintel wrote:
> HiMax HX8837 is a display controller used on OLPC platforms. It controlls
> backlight and is able to capture and freeze a frame when the LCD controller
> (and the rest of the plaform) is powered off.
> 
> This driver is based on the same code as drivers/staging/olpc_dcon.
> I modernized it to use managed GPIO, device-tree bindings, sysfs attribtue
> groups, essentially fixing the staging driver's TODO.
> 
> Why I am not removing the staging driver now is because I've hobbled off
> some functionality too (with an intent to bring add it back eventually):
> 
> * I've removed parts that talk directly to the OLPC EC to turn off/on the
>   power. A separate patch will make the EC expose a regulator interface
>   that should be used instead.
> 
> * Some work is likely needed to make XO 1 and XO 1.5 work. Both platforms
>   are DT-based and could use the same bindings, but I haven't checked
>   whether the cs5535 and vx855 GPIO drivers are good enough.
> 
> What is there is the backlight control and the sysfs attributes to control
> the freeze/unfreeze..
> 
> I've also renamed the driver to use the actual chip name instead of the
> original name that I found too generic. This way the staging driver can be
> used on XO 1 and XO 1.5 for the time being, while my XO 1.75 can utilize
> this one.
> 
> Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
> ---
> Changes since v1:
> - Use interrupt bindings instead of gpio for the IRQ
> - Update the statement on XO 1/1.5 support in the commit message
> 
>  drivers/misc/Kconfig  |  16 +
>  drivers/misc/Makefile |   1 +
>  drivers/misc/hx8837.c | 741 ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 758 insertions(+)
>  create mode 100644 drivers/misc/hx8837.c
> 

Reviewed-by: Rob Herring <robh@kernel.org>

[PATCH 1/2] dt-bindings: himax,hx8837: add HiMax HX8837 bindings

[Lubomir Rintel]

HiMax HX8837 is a display controller used on OLPC platforms.
It controlls backlight and is able to capture and freeze a frame when
the LCD controller (and the rest of the plaform) is powered off.

What is missing here is the description of connections to the LCD
controller and the panel. Maybe it would be a good idea to plug in it
betweend the two in a manner described in
<Documentation/devicetree/bindings/graph.txt>.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
---
 .../devicetree/bindings/misc/himax,hx8837.txt  | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/misc/himax,hx8837.txt

diff --git a/Documentation/devicetree/bindings/misc/himax,hx8837.txt b/Documentation/devicetree/bindings/misc/himax,hx8837.txt
new file mode 100644
index 000000000000..7ffcc516a1b4
--- /dev/null
+++ b/Documentation/devicetree/bindings/misc/himax,hx8837.txt
@@ -0,0 +1,18 @@
+HX8837 Display Controller
+
+Required properties:
+- compatible: Should be "himax,hx8837".
+- reg: I2C address, must be 0x0d
+- stat-gpios: gpio specifier of DCON_STAT0 and DCON_STAT1 pins (active high)
+- load-gpio: gpio specifier of DCON_LOAD pin (active high)
+- irq-gpio: gpio specifier of DCON_IRQ pin (active high)
+
+Example:
+	dcon@d {
+		compatible = "himax,hx8837";
+		reg = <0x0d>;
+		stat-gpios = <&gpio 100 GPIO_ACTIVE_HIGH
+			      &gpio 101 GPIO_ACTIVE_HIGH>;
+		load-gpio = <&gpio 142 GPIO_ACTIVE_HIGH>;
+		irq-gpio = <&gpio 124 GPIO_ACTIVE_HIGH>;
+	};
-- 
2.17.1

[PATCH 2/2] misc: hx8837: add a HiMax HX8837 display controller driver

[Lubomir Rintel]

HiMax HX8837 is a display controller used on OLPC platforms.
It controlls backlight and is able to capture and freeze a frame when
the LCD controller (and the rest of the plaform) is powered off.

This driver is based on the same code as drivers/staging/olpc_dcon.
I modernized it to use managed GPIO, device-tree bindings, sysfs
attribtue groups, essentially fixing the staging driver's TODO.

Why I am not removing the staging driver now is because I've hobbled off
some functionality too (with an intent to bring add it back eventually):

* I've removed parts that talk directly to the OLPC EC to turn off/on
  the power. My platform (OLPC 1.75) doesn't have an EC driver yet
  (in progress!), and perhaps there's a more sensible API that should be
  used (regulator? clock?).

* I couldn't test it with XO 1 and XO 1.5, because I don't have the
  hardware. I think I'll be able to get a XO 1 laptop soonish, which
  will make testing easier.  I guess both platforms are DT-based and
  could use the same bindings.

What is there is the backlight control and the sysfs attributes to
control the freeze/unfreeze..

I've also renamed the driver to use the actual chip name instead of the
original name that I found too generic. This way the staging driver can
be used on XO 1 and XO 1.5, while my XO 1.75 can utilize this one.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
---
 drivers/misc/Kconfig  |  16 +
 drivers/misc/Makefile |   1 +
 drivers/misc/hx8837.c | 749 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 766 insertions(+)
 create mode 100644 drivers/misc/hx8837.c

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 3726eacdf65d..3eb6df0ea0a4 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -513,6 +513,22 @@ config MISC_RTSX
 	tristate
 	default MISC_RTSX_PCI || MISC_RTSX_USB
 
+config HX8837_DCON
+        tristate "HiMax HX8837 Display Controller on OLPC"
+        depends on I2C
+        depends on BACKLIGHT_LCD_SUPPORT
+        select BACKLIGHT_CLASS_DEVICE
+        help
+          In order to support very low power operation, the OLPC XO laptop uses a
+          secondary Display Controller, or DCON.  This secondary controller
+          is present in the video pipeline between the primary display
+          controller (integrate into the processor or chipset) and the LCD
+          panel.  It allows the main processor/display controller to be
+          completely powered off while still retaining an image on the display.
+          This controller is only available on OLPC platforms.
+
+          Unless you have an OLPC XO laptop, you will want to say N.
+
 source "drivers/misc/c2port/Kconfig"
 source "drivers/misc/eeprom/Kconfig"
 source "drivers/misc/cb710/Kconfig"
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index af22bbc3d00c..33689ae496b4 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -58,3 +58,4 @@ obj-$(CONFIG_ASPEED_LPC_SNOOP)	+= aspeed-lpc-snoop.o
 obj-$(CONFIG_PCI_ENDPOINT_TEST)	+= pci_endpoint_test.o
 obj-$(CONFIG_OCXL)		+= ocxl/
 obj-$(CONFIG_MISC_RTSX)		+= cardreader/
+obj-$(CONFIG_HX8837_DCON)	+= hx8837.o
diff --git a/drivers/misc/hx8837.c b/drivers/misc/hx8837.c
new file mode 100644
index 000000000000..3e8924d8c6ec
--- /dev/null
+++ b/drivers/misc/hx8837.c
@@ -0,0 +1,749 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Mainly by David Woodhouse, somewhat modified by Jordan Crouse.
+ * Modernized to use managed GPIO, device-tree, etc. by Lubomir Rintel.
+ *
+ * Copyright (C) 2006-2007  Red Hat, Inc.
+ * Copyright (C) 2006-2007  Advanced Micro Devices, Inc.
+ * Copyright (C) 2009       VIA Technology, Inc.
+ * Copyright (C) 2010-2011  Andres Salomon <dilinger@queued.net>
+ * Copyright (C) 2018       Lubomir Rintel <lkundrak@v3.sk>
+ */
+
+#include <linux/module.h>
+#include <linux/backlight.h>
+#include <linux/console.h>
+#include <linux/ctype.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/fb.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/notifier.h>
+#include <linux/reboot.h>
+
+/* DCON registers */
+
+#define DCON_REG_ID		 0
+#define DCON_REG_MODE		 1
+
+#define MODE_PASSTHRU		BIT(0)
+#define MODE_SLEEP		BIT(1)
+#define MODE_SLEEP_AUTO		BIT(2)
+#define MODE_BL_ENABLE		BIT(3)
+#define MODE_BLANK		BIT(4)
+#define MODE_CSWIZZLE		BIT(5)
+#define MODE_COL_AA		BIT(6)
+#define MODE_MONO_LUMA		BIT(7)
+#define MODE_SCAN_INT		BIT(8)
+#define MODE_CLOCKDIV		BIT(9)
+#define MODE_DEBUG		BIT(14)
+#define MODE_SELFTEST		BIT(15)
+
+#define DCON_REG_HRES		0x2
+#define DCON_REG_HTOTAL		0x3
+#define DCON_REG_HSYNC_WIDTH	0x4
+#define DCON_REG_VRES		0x5
+#define DCON_REG_VTOTAL		0x6
+#define DCON_REG_VSYNC_WIDTH	0x7
+#define DCON_REG_TIMEOUT	0x8
+#define DCON_REG_SCAN_INT	0x9
+#define DCON_REG_BRIGHT		0xa
+#define DCON_REG_MEM_OPT_A	0x41
+#define DCON_REG_MEM_OPT_B	0x42
+
+/* Load Delay Locked Loop (DLL) settings for clock delay */
+#define MEM_DLL_CLOCK_DELAY	BIT(0)
+/* Memory controller power down function */
+#define MEM_POWER_DOWN		BIT(8)
+/* Memory controller software reset */
+#define MEM_SOFT_RESET		BIT(0)
+
+/* Status values */
+
+#define DCONSTAT_SCANINT	0
+#define DCONSTAT_SCANINT_DCON	1
+#define DCONSTAT_DISPLAYLOAD	2
+#define DCONSTAT_MISSED		3
+
+/* Source values */
+
+#define DCON_SOURCE_DCON        0
+#define DCON_SOURCE_CPU         1
+
+struct hx8837_priv {
+	struct i2c_client *client;
+	struct fb_info *fbinfo;
+	struct backlight_device *bl_dev;
+
+	wait_queue_head_t waitq;
+	struct work_struct switch_source;
+	struct notifier_block reboot_nb;
+	struct notifier_block panic_nb;
+
+	/* Scanline to interrupt on during resume */
+	ushort resumeline;
+
+	/* Shadow register for the DCON_REG_MODE register */
+	u8 disp_mode;
+
+	/* The current backlight value - this saves us some smbus traffic */
+	u8 bl_val;
+
+	/* Current source, initialized at probe time */
+	int curr_src;
+
+	/* Desired source */
+	int pending_src;
+
+	/* Variables used during switches */
+	bool switched;
+	ktime_t irq_time;
+	ktime_t load_time;
+
+	/* Current output type; true == mono, false == color */
+	bool mono;
+	/* This get set while controlling fb blank state from the driver */
+	bool ignore_fb_events;
+
+	struct gpio_desc *stat0_gpio;
+	struct gpio_desc *stat1_gpio;
+	struct gpio_desc *load_gpio;
+	struct gpio_desc *irq_gpio;
+};
+
+static irqreturn_t hx8837_interrupt(int irq, void *id);
+
+/* I2C structures */
+
+static unsigned short normal_i2c[] = { 0x0d, I2C_CLIENT_END };
+
+static s32 hx8837_write(struct hx8837_priv *priv, u8 reg, u16 val)
+{
+	return i2c_smbus_write_word_data(priv->client, reg, val);
+}
+
+static s32 hx8837_read(struct hx8837_priv *priv, u8 reg)
+{
+	return i2c_smbus_read_word_data(priv->client, reg);
+}
+
+static void hx8837_hw_init(struct hx8837_priv *priv, int is_init)
+{
+	/* SDRAM setup/hold time */
+	hx8837_write(priv, 0x3a, 0xc040);
+	hx8837_write(priv, DCON_REG_MEM_OPT_A, 0x0000);  /* clear option bits */
+	hx8837_write(priv, DCON_REG_MEM_OPT_A,
+		   MEM_DLL_CLOCK_DELAY | MEM_POWER_DOWN);
+	hx8837_write(priv, DCON_REG_MEM_OPT_B, MEM_SOFT_RESET);
+
+	/* Colour swizzle, AA, no passthrough, backlight */
+	if (is_init) {
+		priv->disp_mode = MODE_PASSTHRU | MODE_BL_ENABLE |
+				MODE_CSWIZZLE | MODE_COL_AA;
+	}
+	hx8837_write(priv, DCON_REG_MODE, priv->disp_mode);
+
+	/* Set the scanline to interrupt on during resume */
+	hx8837_write(priv, DCON_REG_SCAN_INT, priv->resumeline);
+}
+
+static void hx8837_set_backlight(struct hx8837_priv *priv, u8 level)
+{
+	hx8837_write(priv, DCON_REG_BRIGHT, level);
+
+	/* Purposely turn off the backlight when we go to level 0 */
+	if (level == 0) {
+		priv->disp_mode &= ~MODE_BL_ENABLE;
+		hx8837_write(priv, DCON_REG_MODE, priv->disp_mode);
+	} else if (!(priv->disp_mode & MODE_BL_ENABLE)) {
+		priv->disp_mode |= MODE_BL_ENABLE;
+		hx8837_write(priv, DCON_REG_MODE, priv->disp_mode);
+	}
+}
+
+/* Set the output type to either color or mono */
+static int hx8837_set_mono_mode(struct hx8837_priv *priv, bool enable_mono)
+{
+	if (priv->mono == enable_mono)
+		return 0;
+
+	priv->mono = enable_mono;
+
+	if (enable_mono) {
+		priv->disp_mode &= ~(MODE_CSWIZZLE | MODE_COL_AA);
+		priv->disp_mode |= MODE_MONO_LUMA;
+	} else {
+		priv->disp_mode &= ~(MODE_MONO_LUMA);
+		priv->disp_mode |= MODE_CSWIZZLE | MODE_COL_AA;
+	}
+
+	hx8837_write(priv, DCON_REG_MODE, priv->disp_mode);
+	return 0;
+}
+
+/* the DCON seems to get confused if we change DCONLOAD too
+ * frequently -- i.e., approximately faster than frame time.
+ * normally we don't change it this fast, so in general we won't
+ * delay here.
+ */
+static void hx8837_load_holdoff(struct hx8837_priv *priv)
+{
+	ktime_t delta_t, now;
+
+	while (1) {
+		now = ktime_get();
+		delta_t = ktime_sub(now, priv->load_time);
+		if (ktime_to_ns(delta_t) > NSEC_PER_MSEC * 20)
+			break;
+		mdelay(4);
+	}
+}
+
+static bool hx8837_blank_fb(struct hx8837_priv *priv, bool blank)
+{
+	int err;
+
+	console_lock();
+	if (!lock_fb_info(priv->fbinfo)) {
+		console_unlock();
+		dev_err(&priv->client->dev, "unable to lock framebuffer\n");
+		return false;
+	}
+
+	priv->ignore_fb_events = true;
+	err = fb_blank(priv->fbinfo,
+		       blank ? FB_BLANK_POWERDOWN : FB_BLANK_UNBLANK);
+	priv->ignore_fb_events = false;
+	unlock_fb_info(priv->fbinfo);
+	console_unlock();
+
+	if (err) {
+		dev_err(&priv->client->dev, "couldn't %sblank framebuffer\n",
+			blank ? "" : "un");
+		return false;
+	}
+	return true;
+}
+
+/* Set the source of the display (CPU or DCON) */
+static void hx8837_source_switch(struct work_struct *work)
+{
+	struct hx8837_priv *priv = container_of(work, struct hx8837_priv,
+							switch_source);
+	struct device *dev = &priv->client->dev;
+	int source = priv->pending_src;
+
+	if (priv->curr_src == source)
+		return;
+
+	hx8837_load_holdoff(priv);
+
+	priv->switched = false;
+
+	switch (source) {
+	case DCON_SOURCE_CPU:
+		dev_info(dev, "%s to CPU\n", __func__);
+		/* Enable the scanline interrupt bit */
+		if (hx8837_write(priv, DCON_REG_MODE,
+			       priv->disp_mode | MODE_SCAN_INT))
+			dev_err(dev, "couldn't enable scanline interrupt!\n");
+		else
+			/* Wait up to one second for the scanline interrupt */
+			wait_event_timeout(priv->waitq, priv->switched, HZ);
+
+		if (!priv->switched)
+			dev_err(dev, "Timeout entering CPU mode; expect a screen glitch.\n");
+
+		/* Turn off the scanline interrupt */
+		if (hx8837_write(priv, DCON_REG_MODE, priv->disp_mode))
+			dev_err(dev, "couldn't disable scanline interrupt!\n");
+
+		/*
+		 * Ideally we'd like to disable interrupts here so that the
+		 * fb unblanking and DCON turn on happen at a known time value;
+		 * however, we can't do that right now with fb_blank
+		 * messing with semaphores.
+		 *
+		 * For now, we just hope..
+		 */
+		if (!hx8837_blank_fb(priv, false)) {
+			dev_err(dev, "Failed to enter CPU mode\n");
+			priv->pending_src = DCON_SOURCE_DCON;
+			return;
+		}
+
+		/* And turn off the DCON */
+		gpiod_set_value(priv->load_gpio, 1);
+		priv->load_time = ktime_get();
+
+		dev_info(dev, "The CPU has control\n");
+		break;
+	case DCON_SOURCE_DCON:
+		dev_info(dev, "%s to DCON\n", __func__);
+
+		/* Clear DCONLOAD - this implies that the DCON is in control */
+		gpiod_set_value(priv->load_gpio, 0);
+		priv->load_time = ktime_get();
+
+		wait_event_timeout(priv->waitq, priv->switched, HZ / 2);
+
+		if (!priv->switched) {
+			dev_err(dev, "Timeout entering DCON mode; expect a screen glitch.\n");
+		} else {
+			ktime_t delta_t;
+
+			/* sometimes the DCON doesn't follow its own rules,
+			 * and doesn't wait for two vsync pulses before
+			 * ack'ing the frame load with an IRQ.  the result
+			 * is that the display shows the *previously*
+			 * loaded frame.  we can detect this by looking at
+			 * the time between asserting DCONLOAD and the IRQ --
+			 * if it's less than 20msec, then the DCON couldn't
+			 * have seen two VSYNC pulses.  in that case we
+			 * deassert and reassert, and hope for the best.
+			 * see http://dev.laptop.org/ticket/9664
+			 */
+			delta_t = ktime_sub(priv->irq_time, priv->load_time);
+			if (priv->switched && ktime_to_ns(delta_t)
+			    < NSEC_PER_MSEC * 20) {
+				dev_err(dev, "missed loading, retrying\n");
+				gpiod_set_value(priv->load_gpio, 1);
+				mdelay(41);
+				gpiod_set_value(priv->load_gpio, 0);
+				priv->load_time = ktime_get();
+				mdelay(41);
+			}
+		}
+
+		hx8837_blank_fb(priv, true);
+		dev_info(dev, "The DCON has control\n");
+		break;
+	default:
+		WARN_ON(1);
+	}
+
+	priv->curr_src = source;
+}
+
+static void hx8837_set_source(struct hx8837_priv *priv, int arg)
+{
+	if (priv->pending_src == arg)
+		return;
+
+	priv->pending_src = arg;
+
+	if (priv->curr_src != arg)
+		schedule_work(&priv->switch_source);
+}
+
+static void hx8837_set_source_sync(struct hx8837_priv *priv, int arg)
+{
+	hx8837_set_source(priv, arg);
+	flush_scheduled_work();
+}
+
+static int hx8837_bl_update(struct backlight_device *dev)
+{
+	struct hx8837_priv *priv = bl_get_data(dev);
+	u8 level = dev->props.brightness & 0x0F;
+
+	priv->bl_val = level;
+
+	if (dev->props.power != FB_BLANK_UNBLANK)
+		level = 0;
+
+	if (dev->props.state & BL_CORE_FBBLANK)
+		level = 0;
+
+	hx8837_set_backlight(priv, level);
+
+	return 0;
+}
+
+static int hx8837_bl_get(struct backlight_device *dev)
+{
+	struct hx8837_priv *priv = bl_get_data(dev);
+
+	return priv->bl_val;
+}
+
+static const struct backlight_ops hx8837_bl_ops = {
+	.update_status = hx8837_bl_update,
+	.get_brightness = hx8837_bl_get,
+};
+
+static struct backlight_properties hx8837_bl_props = {
+	.max_brightness = 15,
+	.type = BACKLIGHT_RAW,
+	.power = FB_BLANK_UNBLANK,
+};
+
+static int hx8837_reboot_notify(struct notifier_block *nb, unsigned long foo,
+								void *bar)
+{
+	struct hx8837_priv *priv = container_of(nb, struct hx8837_priv,
+								reboot_nb);
+
+	/* Turn off the DCON. Entirely. */
+	hx8837_write(priv, DCON_REG_MODE, 0x39);
+	hx8837_write(priv, DCON_REG_MODE, 0x32);
+	return NOTIFY_DONE;
+}
+
+static int hx8837_panic_notify(struct notifier_block *nb, unsigned long e,
+								void *p)
+{
+	struct hx8837_priv *priv = container_of(nb, struct hx8837_priv,
+								panic_nb);
+
+	gpiod_set_value(priv->load_gpio, 1);
+	return NOTIFY_DONE;
+}
+
+static int hx8837_detect(struct i2c_client *client, struct i2c_board_info *info)
+{
+	strlcpy(info->type, "hx8837", I2C_NAME_SIZE);
+
+	return 0;
+}
+
+static ssize_t mode_show(struct device *dev, struct device_attribute *attr,
+								char *buf)
+{
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%4.4X\n", priv->disp_mode);
+}
+
+static ssize_t freeze_show(struct device *dev, struct device_attribute *attr,
+								char *buf)
+{
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", priv->curr_src == DCON_SOURCE_DCON ? 1 : 0);
+}
+
+static ssize_t monochrome_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", priv->mono);
+}
+
+static ssize_t resumeline_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", priv->resumeline);
+}
+
+static ssize_t monochrome_store(struct device *dev,
+			struct device_attribute *attr,
+			const char *buf, size_t count)
+{
+	unsigned long enable_mono;
+	int rc;
+
+	rc = kstrtoul(buf, 10, &enable_mono);
+	if (rc)
+		return rc;
+
+	hx8837_set_mono_mode(dev_get_drvdata(dev), enable_mono ? true : false);
+
+	return count;
+}
+
+static ssize_t freeze_store(struct device *dev, struct device_attribute *attr,
+						const char *buf, size_t count)
+{
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+	unsigned long output;
+	int ret;
+
+	ret = kstrtoul(buf, 10, &output);
+	if (ret)
+		return ret;
+
+	switch (output) {
+	case 0:
+		hx8837_set_source(priv, DCON_SOURCE_CPU);
+		break;
+	case 1:
+		hx8837_set_source_sync(priv, DCON_SOURCE_DCON);
+		break;
+	case 2:  /* normally unused */
+		hx8837_set_source(priv, DCON_SOURCE_DCON);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return count;
+}
+
+static ssize_t resumeline_store(struct device *dev,
+			struct device_attribute *attr,
+			const char *buf, size_t count)
+{
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+	unsigned short rl;
+	int rc;
+
+	rc = kstrtou16(buf, 10, &rl);
+	if (rc)
+		return rc;
+
+	priv->resumeline = rl;
+	hx8837_write(dev_get_drvdata(dev), DCON_REG_SCAN_INT, priv->resumeline);
+
+	return count;
+}
+
+
+static DEVICE_ATTR_RO(mode);
+static DEVICE_ATTR_RW(freeze);
+static DEVICE_ATTR_RW(monochrome);
+static DEVICE_ATTR_RW(resumeline);
+
+static struct attribute *hx8837_attrs[] = {
+	&dev_attr_mode.attr,
+	&dev_attr_freeze.attr,
+	&dev_attr_monochrome.attr,
+	&dev_attr_resumeline.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(hx8837);
+
+static int hx8837_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	struct hx8837_priv *priv;
+	u16 ver;
+	int rc;
+
+	if (num_registered_fb < 1)
+		return -EPROBE_DEFER;
+
+	priv = devm_kzalloc(&client->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->client = client;
+	init_waitqueue_head(&priv->waitq);
+	INIT_WORK(&priv->switch_source, hx8837_source_switch);
+	priv->reboot_nb.notifier_call = hx8837_reboot_notify;
+	priv->reboot_nb.priority = -1;
+	priv->panic_nb.notifier_call = hx8837_panic_notify;
+
+	/*
+	 * Perhaps we could add a phandle to the panel to a DT property so that
+	 * we'll be able to guess it from the vertical resolution instead of
+	 * hardwiring it?
+	 */
+	priv->resumeline = 898;
+
+	i2c_set_clientdata(client, priv);
+
+	priv->fbinfo = registered_fb[0];
+
+	priv->stat0_gpio = devm_gpiod_get_index(&client->dev, "stat", 0,
+								GPIOD_IN);
+	if (IS_ERR(priv->stat0_gpio)) {
+		dev_err(&client->dev, "failed to request STAT0 GPIO\n");
+		return PTR_ERR(priv->stat0_gpio);
+	};
+
+	priv->stat1_gpio = devm_gpiod_get_index(&client->dev, "stat", 1,
+								GPIOD_IN);
+	if (IS_ERR(priv->stat1_gpio)) {
+		dev_err(&client->dev, "failed to request STAT1 GPIO\n");
+		return PTR_ERR(priv->stat1_gpio);
+	};
+
+	priv->load_gpio = devm_gpiod_get(&client->dev, "load", GPIOD_IN);
+	if (IS_ERR(priv->load_gpio)) {
+		dev_err(&client->dev, "failed to request LOAD GPIO\n");
+		return PTR_ERR(priv->load_gpio);
+	};
+
+	priv->irq_gpio = devm_gpiod_get(&client->dev, "irq", GPIOD_IN);
+	if (IS_ERR(priv->irq_gpio)) {
+		dev_err(&client->dev, "failed to request IRQ GPIO\n");
+		return PTR_ERR(priv->irq_gpio);
+	};
+
+	ver = hx8837_read(priv, DCON_REG_ID);
+	if ((ver >> 8) != 0xDC) {
+		dev_err(&client->dev, "DCON ID not 0xDCxx: 0x%04x.\n", ver);
+		return -ENXIO;
+	}
+
+	dev_info(&client->dev, "Discovered DCON version %x\n", ver & 0xFF);
+
+	if (ver < 0xdc02) {
+		dev_err(&client->dev, "DCON v1 is unsupported, giving up.\n");
+		return -ENODEV;
+	}
+
+	/*
+	 * Determine the current state by reading the GPIO bit; earlier
+	 * stages of the boot process have established the state.
+	 */
+	priv->curr_src = gpiod_get_value(priv->load_gpio)
+			? DCON_SOURCE_CPU : DCON_SOURCE_DCON;
+	priv->pending_src = priv->curr_src;
+
+	/* Set the directions for the GPIO pins */
+	gpiod_direction_input(priv->stat0_gpio);
+	gpiod_direction_input(priv->stat1_gpio);
+	gpiod_direction_input(priv->irq_gpio);
+	gpiod_direction_output(priv->load_gpio,
+		priv->curr_src == DCON_SOURCE_CPU);
+
+	/* Register the interrupt handler */
+	rc = devm_request_irq(&client->dev, gpiod_to_irq(priv->irq_gpio),
+			&hx8837_interrupt, IRQF_TRIGGER_FALLING, "DCON", priv);
+	if (rc) {
+		dev_err(&client->dev, "failed to request DCON's irq\n");
+		return rc;
+	}
+
+	hx8837_hw_init(priv, 1);
+
+	priv->bl_val = hx8837_read(priv, DCON_REG_BRIGHT) & 0x0F;
+
+	/* Add the backlight device for the DCON */
+	hx8837_bl_props.brightness = priv->bl_val;
+	priv->bl_dev = devm_backlight_device_register(&client->dev, "hx8837-bl",
+			&client->dev, priv, &hx8837_bl_ops, &hx8837_bl_props);
+	if (IS_ERR(priv->bl_dev)) {
+		dev_err(&client->dev, "cannot register backlight dev (%ld)\n",
+			PTR_ERR(priv->bl_dev));
+		priv->bl_dev = NULL;
+	}
+
+	rc = devm_device_add_groups(&client->dev, hx8837_groups);
+	if (rc) {
+		dev_err(&client->dev, "failed to register sysfs groups\n");
+		return rc;
+	}
+
+	devm_register_reboot_notifier(&client->dev, &priv->reboot_nb);
+	atomic_notifier_chain_register(&panic_notifier_list, &priv->panic_nb);
+
+	return 0;
+}
+
+static int hx8837_remove(struct i2c_client *client)
+{
+	struct hx8837_priv *priv = i2c_get_clientdata(client);
+
+	atomic_notifier_chain_unregister(&panic_notifier_list,
+					&priv->panic_nb);
+
+	cancel_work_sync(&priv->switch_source);
+
+	return 0;
+}
+
+static irqreturn_t hx8837_interrupt(int irq, void *id)
+{
+	struct hx8837_priv *priv = id;
+	struct device *dev = &priv->client->dev;
+	u8 status;
+
+	status = gpiod_get_value(priv->stat0_gpio);
+	status |= gpiod_get_value(priv->stat1_gpio) << 1;
+
+
+	switch (status & 3) {
+	case 3:
+		dev_dbg(dev, "DCONLOAD_MISSED interrupt\n");
+		break;
+
+	case 2:	/* switch to DCON mode */
+	case 1: /* switch to CPU mode */
+		priv->switched = true;
+		priv->irq_time = ktime_get();
+		wake_up(&priv->waitq);
+		break;
+
+	case 0:
+		/* workaround resume case:  the DCON (on 1.5) doesn't
+		 * ever assert status 0x01 when switching to CPU mode
+		 * during resume.  this is because DCONLOAD is de-asserted
+		 * _immediately_ upon exiting S3, so the actual release
+		 * of the DCON happened long before this point.
+		 * see http://dev.laptop.org/ticket/9869
+		 */
+		if (priv->curr_src != priv->pending_src && !priv->switched) {
+			priv->switched = true;
+			priv->irq_time = ktime_get();
+			wake_up(&priv->waitq);
+			dev_dbg(dev, "switching w/ status 0/0\n");
+		} else {
+			dev_dbg(dev, "scanline interrupt w/CPU\n");
+		}
+	}
+
+	return IRQ_HANDLED;
+}
+
+#ifdef CONFIG_PM
+static int hx8837_suspend(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct hx8837_priv *priv = i2c_get_clientdata(client);
+
+	hx8837_set_source_sync(priv, DCON_SOURCE_DCON);
+
+	return 0;
+}
+
+static int hx8837_resume(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct hx8837_priv *priv = i2c_get_clientdata(client);
+
+	hx8837_set_source(priv, DCON_SOURCE_CPU);
+
+	return 0;
+}
+#endif /* CONFIG_PM */
+
+static SIMPLE_DEV_PM_OPS(hx8837_pm_ops, hx8837_suspend, hx8837_resume);
+
+static const struct of_device_id hx8837_dt_ids[] = {
+	{ .compatible = "himax,hx8837", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, hx8837_dt_ids);
+
+static const struct i2c_device_id hx8837_i2c_ids[] = {
+	{ .name = "hx8837", },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, hx8837_i2c_ids);
+
+static struct i2c_driver hx8837_driver = {
+	.driver = {
+		.name = "hx8837",
+		.pm = &hx8837_pm_ops,
+		.of_match_table = hx8837_dt_ids,
+	},
+	.class = I2C_CLASS_DDC | I2C_CLASS_HWMON,
+	.id_table = hx8837_i2c_ids,
+	.probe = hx8837_probe,
+	.remove = hx8837_remove,
+	.detect = hx8837_detect,
+	.address_list = normal_i2c,
+};
+
+module_i2c_driver(hx8837_driver);
+
+MODULE_DESCRIPTION("HX8837 Display Controller Driver");
+MODULE_LICENSE("GPL v2");
-- 
2.17.1