Revert "Staging: olpc_dcon: Remove obsolete driver"

This reverts commit 82ef33af9dd30075adbd9f3dd161b606b8ba88ac.  It turns
out these machines are still out there, and the original patch broke
them.  So revert it, adding back the driver, so people's machines still
work properly.

Reported-by: James Cameron <quozl@laptop.org>
Cc: Shraddha Barke <shraddha.6596@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

9 files changed, 1343 insertions, 0 deletions

diff --git a/drivers/staging/Kconfig b/drivers/staging/Kconfig
index cf84581287b9..5bac28a3944e 100644
--- a/drivers/staging/Kconfig
+++ b/drivers/staging/Kconfig
@@ -30,6 +30,8 @@ source "drivers/staging/wlan-ng/Kconfig"
 
 source "drivers/staging/comedi/Kconfig"
 
+source "drivers/staging/olpc_dcon/Kconfig"
+
 source "drivers/staging/rtl8192u/Kconfig"
 
 source "drivers/staging/rtl8192e/Kconfig"
diff --git a/drivers/staging/Makefile b/drivers/staging/Makefile
index 7d6448d20464..a954242b0f2c 100644
--- a/drivers/staging/Makefile
+++ b/drivers/staging/Makefile
@@ -4,6 +4,7 @@ obj-y				+= media/
 obj-$(CONFIG_SLICOSS)		+= slicoss/
 obj-$(CONFIG_PRISM2_USB)	+= wlan-ng/
 obj-$(CONFIG_COMEDI)		+= comedi/
+obj-$(CONFIG_FB_OLPC_DCON)	+= olpc_dcon/
 obj-$(CONFIG_RTL8192U)		+= rtl8192u/
 obj-$(CONFIG_RTL8192E)		+= rtl8192e/
 obj-$(CONFIG_R8712U)		+= rtl8712/
diff --git a/drivers/staging/olpc_dcon/Kconfig b/drivers/staging/olpc_dcon/Kconfig
new file mode 100644
index 000000000000..d277f048789e
--- /dev/null
+++ b/drivers/staging/olpc_dcon/Kconfig
@@ -0,0 +1,35 @@
+config FB_OLPC_DCON
+	tristate "One Laptop Per Child Display CONtroller support"
+	depends on OLPC && FB
+	depends on I2C
+	depends on (GPIO_CS5535 || GPIO_CS5535=n)
+	select BACKLIGHT_CLASS_DEVICE
+	---help---
+	  In order to support very low power operation, the XO laptop uses a
+	  secondary Display CONtroller, or DCON.  This secondary controller
+	  is present in the video pipeline between the primary display
+	  controller (integrate into the processor or chipset) and the LCD
+	  panel.  It allows the main processor/display controller to be
+	  completely powered off while still retaining an image on the display.
+	  This controller is only available on OLPC platforms.  Unless you have
+	  one of these platforms, you will want to say 'N'.
+
+config FB_OLPC_DCON_1
+	bool "OLPC XO-1 DCON support"
+	depends on FB_OLPC_DCON && GPIO_CS5535
+	default y
+	---help---
+	  Enable support for the DCON in XO-1 model laptops.  The kernel
+	  communicates with the DCON using model-specific code.  If you
+	  have an XO-1 (or if you're unsure what model you have), you should
+	  say 'Y'.
+
+config FB_OLPC_DCON_1_5
+	bool "OLPC XO-1.5 DCON support"
+	depends on FB_OLPC_DCON && ACPI
+	default y
+	---help---
+	  Enable support for the DCON in XO-1.5 model laptops.  The kernel
+	  communicates with the DCON using model-specific code.  If you
+	  have an XO-1.5 (or if you're unsure what model you have), you
+	  should say 'Y'.
diff --git a/drivers/staging/olpc_dcon/Makefile b/drivers/staging/olpc_dcon/Makefile
new file mode 100644
index 000000000000..36c7e67fec20
--- /dev/null
+++ b/drivers/staging/olpc_dcon/Makefile
@@ -0,0 +1,6 @@
+olpc-dcon-objs += olpc_dcon.o
+olpc-dcon-$(CONFIG_FB_OLPC_DCON_1)	+= olpc_dcon_xo_1.o
+olpc-dcon-$(CONFIG_FB_OLPC_DCON_1_5)	+= olpc_dcon_xo_1_5.o
+obj-$(CONFIG_FB_OLPC_DCON)	+= olpc-dcon.o
+
+
diff --git a/drivers/staging/olpc_dcon/TODO b/drivers/staging/olpc_dcon/TODO
new file mode 100644
index 000000000000..61c2e65ac354
--- /dev/null
+++ b/drivers/staging/olpc_dcon/TODO
@@ -0,0 +1,9 @@
+TODO:
+	- see if vx855 gpio API can be made similar enough to cs5535 so we can
+	  share more code
+	- allow simultaneous XO-1 and XO-1.5 support
+
+Please send patches to Greg Kroah-Hartman <greg@kroah.com> and
+copy:
+	Daniel Drake <dsd@laptop.org>
+	Jens Frederich <jfrederich@gmail.com>
diff --git a/drivers/staging/olpc_dcon/olpc_dcon.c b/drivers/staging/olpc_dcon/olpc_dcon.c
new file mode 100644
index 000000000000..f45b2ef05f48
--- /dev/null
+++ b/drivers/staging/olpc_dcon/olpc_dcon.c
@@ -0,0 +1,813 @@
+/*
+ * Mainly by David Woodhouse, somewhat modified by Jordan Crouse
+ *
+ * Copyright © 2006-2007  Red Hat, Inc.
+ * Copyright © 2006-2007  Advanced Micro Devices, Inc.
+ * Copyright © 2009       VIA Technology, Inc.
+ * Copyright (c) 2010-2011  Andres Salomon <dilinger@queued.net>
+ *
+ * This program is free software.  You can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/fb.h>
+#include <linux/console.h>
+#include <linux/i2c.h>
+#include <linux/platform_device.h>
+#include <linux/interrupt.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/backlight.h>
+#include <linux/device.h>
+#include <linux/uaccess.h>
+#include <linux/ctype.h>
+#include <linux/reboot.h>
+#include <linux/olpc-ec.h>
+#include <asm/tsc.h>
+#include <asm/olpc.h>
+
+#include "olpc_dcon.h"
+
+/* Module definitions */
+
+static ushort resumeline = 898;
+module_param(resumeline, ushort, 0444);
+
+static struct dcon_platform_data *pdata;
+
+/* I2C structures */
+
+/* Platform devices */
+static struct platform_device *dcon_device;
+
+static unsigned short normal_i2c[] = { 0x0d, I2C_CLIENT_END };
+
+static s32 dcon_write(struct dcon_priv *dcon, u8 reg, u16 val)
+{
+	return i2c_smbus_write_word_data(dcon->client, reg, val);
+}
+
+static s32 dcon_read(struct dcon_priv *dcon, u8 reg)
+{
+	return i2c_smbus_read_word_data(dcon->client, reg);
+}
+
+/* ===== API functions - these are called by a variety of users ==== */
+
+static int dcon_hw_init(struct dcon_priv *dcon, int is_init)
+{
+	u16 ver;
+	int rc = 0;
+
+	ver = dcon_read(dcon, DCON_REG_ID);
+	if ((ver >> 8) != 0xDC) {
+		pr_err("DCON ID not 0xDCxx: 0x%04x instead.\n", ver);
+		rc = -ENXIO;
+		goto err;
+	}
+
+	if (is_init) {
+		pr_info("Discovered DCON version %x\n", ver & 0xFF);
+		rc = pdata->init(dcon);
+		if (rc != 0) {
+			pr_err("Unable to init.\n");
+			goto err;
+		}
+	}
+
+	if (ver < 0xdc02) {
+		dev_err(&dcon->client->dev,
+				"DCON v1 is unsupported, giving up..\n");
+		rc = -ENODEV;
+		goto err;
+	}
+
+	/* SDRAM setup/hold time */
+	dcon_write(dcon, 0x3a, 0xc040);
+	dcon_write(dcon, DCON_REG_MEM_OPT_A, 0x0000);  /* clear option bits */
+	dcon_write(dcon, DCON_REG_MEM_OPT_A,
+				MEM_DLL_CLOCK_DELAY | MEM_POWER_DOWN);
+	dcon_write(dcon, DCON_REG_MEM_OPT_B, MEM_SOFT_RESET);
+
+	/* Colour swizzle, AA, no passthrough, backlight */
+	if (is_init) {
+		dcon->disp_mode = MODE_PASSTHRU | MODE_BL_ENABLE |
+				MODE_CSWIZZLE | MODE_COL_AA;
+	}
+	dcon_write(dcon, DCON_REG_MODE, dcon->disp_mode);
+
+	/* Set the scanline to interrupt on during resume */
+	dcon_write(dcon, DCON_REG_SCAN_INT, resumeline);
+
+err:
+	return rc;
+}
+
+/*
+ * The smbus doesn't always come back due to what is believed to be
+ * hardware (power rail) bugs.  For older models where this is known to
+ * occur, our solution is to attempt to wait for the bus to stabilize;
+ * if it doesn't happen, cut power to the dcon, repower it, and wait
+ * for the bus to stabilize.  Rinse, repeat until we have a working
+ * smbus.  For newer models, we simply BUG(); we want to know if this
+ * still happens despite the power fixes that have been made!
+ */
+static int dcon_bus_stabilize(struct dcon_priv *dcon, int is_powered_down)
+{
+	unsigned long timeout;
+	u8 pm;
+	int x;
+
+power_up:
+	if (is_powered_down) {
+		pm = 1;
+		x = olpc_ec_cmd(EC_DCON_POWER_MODE, &pm, 1, NULL, 0);
+		if (x) {
+			pr_warn("unable to force dcon to power up: %d!\n", x);
+			return x;
+		}
+		usleep_range(10000, 11000);  /* we'll be conservative */
+	}
+
+	pdata->bus_stabilize_wiggle();
+
+	for (x = -1, timeout = 50; timeout && x < 0; timeout--) {
+		usleep_range(1000, 1100);
+		x = dcon_read(dcon, DCON_REG_ID);
+	}
+	if (x < 0) {
+		pr_err("unable to stabilize dcon's smbus, reasserting power and praying.\n");
+		BUG_ON(olpc_board_at_least(olpc_board(0xc2)));
+		pm = 0;
+		olpc_ec_cmd(EC_DCON_POWER_MODE, &pm, 1, NULL, 0);
+		msleep(100);
+		is_powered_down = 1;
+		goto power_up;	/* argh, stupid hardware.. */
+	}
+
+	if (is_powered_down)
+		return dcon_hw_init(dcon, 0);
+	return 0;
+}
+
+static void dcon_set_backlight(struct dcon_priv *dcon, u8 level)
+{
+	dcon->bl_val = level;
+	dcon_write(dcon, DCON_REG_BRIGHT, dcon->bl_val);
+
+	/* Purposely turn off the backlight when we go to level 0 */
+	if (dcon->bl_val == 0) {
+		dcon->disp_mode &= ~MODE_BL_ENABLE;
+		dcon_write(dcon, DCON_REG_MODE, dcon->disp_mode);
+	} else if (!(dcon->disp_mode & MODE_BL_ENABLE)) {
+		dcon->disp_mode |= MODE_BL_ENABLE;
+		dcon_write(dcon, DCON_REG_MODE, dcon->disp_mode);
+	}
+}
+
+/* Set the output type to either color or mono */
+static int dcon_set_mono_mode(struct dcon_priv *dcon, bool enable_mono)
+{
+	if (dcon->mono == enable_mono)
+		return 0;
+
+	dcon->mono = enable_mono;
+
+	if (enable_mono) {
+		dcon->disp_mode &= ~(MODE_CSWIZZLE | MODE_COL_AA);
+		dcon->disp_mode |= MODE_MONO_LUMA;
+	} else {
+		dcon->disp_mode &= ~(MODE_MONO_LUMA);
+		dcon->disp_mode |= MODE_CSWIZZLE | MODE_COL_AA;
+	}
+
+	dcon_write(dcon, DCON_REG_MODE, dcon->disp_mode);
+	return 0;
+}
+
+/* For now, this will be really stupid - we need to address how
+ * DCONLOAD works in a sleep and account for it accordingly
+ */
+
+static void dcon_sleep(struct dcon_priv *dcon, bool sleep)
+{
+	int x;
+
+	/* Turn off the backlight and put the DCON to sleep */
+
+	if (dcon->asleep == sleep)
+		return;
+
+	if (!olpc_board_at_least(olpc_board(0xc2)))
+		return;
+
+	if (sleep) {
+		u8 pm = 0;
+
+		x = olpc_ec_cmd(EC_DCON_POWER_MODE, &pm, 1, NULL, 0);
+		if (x)
+			pr_warn("unable to force dcon to power down: %d!\n", x);
+		else
+			dcon->asleep = sleep;
+	} else {
+		/* Only re-enable the backlight if the backlight value is set */
+		if (dcon->bl_val != 0)
+			dcon->disp_mode |= MODE_BL_ENABLE;
+		x = dcon_bus_stabilize(dcon, 1);
+		if (x)
+			pr_warn("unable to reinit dcon hardware: %d!\n", x);
+		else
+			dcon->asleep = sleep;
+
+		/* Restore backlight */
+		dcon_set_backlight(dcon, dcon->bl_val);
+	}
+
+	/* We should turn off some stuff in the framebuffer - but what? */
+}
+
+/* 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 dcon_load_holdoff(struct dcon_priv *dcon)
+{
+	ktime_t delta_t, now;
+
+	while (1) {
+		now = ktime_get();
+		delta_t = ktime_sub(now, dcon->load_time);
+		if (ktime_to_ns(delta_t) > NSEC_PER_MSEC * 20)
+			break;
+		mdelay(4);
+	}
+}
+
+static bool dcon_blank_fb(struct dcon_priv *dcon, bool blank)
+{
+	int err;
+
+	console_lock();
+	if (!lock_fb_info(dcon->fbinfo)) {
+		console_unlock();
+		dev_err(&dcon->client->dev, "unable to lock framebuffer\n");
+		return false;
+	}
+
+	dcon->ignore_fb_events = true;
+	err = fb_blank(dcon->fbinfo,
+			blank ? FB_BLANK_POWERDOWN : FB_BLANK_UNBLANK);
+	dcon->ignore_fb_events = false;
+	unlock_fb_info(dcon->fbinfo);
+	console_unlock();
+
+	if (err) {
+		dev_err(&dcon->client->dev, "couldn't %sblank framebuffer\n",
+				blank ? "" : "un");
+		return false;
+	}
+	return true;
+}
+
+/* Set the source of the display (CPU or DCON) */
+static void dcon_source_switch(struct work_struct *work)
+{
+	struct dcon_priv *dcon = container_of(work, struct dcon_priv,
+			switch_source);
+	int source = dcon->pending_src;
+
+	if (dcon->curr_src == source)
+		return;
+
+	dcon_load_holdoff(dcon);
+
+	dcon->switched = false;
+
+	switch (source) {
+	case DCON_SOURCE_CPU:
+		pr_info("dcon_source_switch to CPU\n");
+		/* Enable the scanline interrupt bit */
+		if (dcon_write(dcon, DCON_REG_MODE,
+				dcon->disp_mode | MODE_SCAN_INT))
+			pr_err("couldn't enable scanline interrupt!\n");
+		else
+			/* Wait up to one second for the scanline interrupt */
+			wait_event_timeout(dcon->waitq, dcon->switched, HZ);
+
+		if (!dcon->switched)
+			pr_err("Timeout entering CPU mode; expect a screen glitch.\n");
+
+		/* Turn off the scanline interrupt */
+		if (dcon_write(dcon, DCON_REG_MODE, dcon->disp_mode))
+			pr_err("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 (!dcon_blank_fb(dcon, false)) {
+			pr_err("Failed to enter CPU mode\n");
+			dcon->pending_src = DCON_SOURCE_DCON;
+			return;
+		}
+
+		/* And turn off the DCON */
+		pdata->set_dconload(1);
+		dcon->load_time = ktime_get();
+
+		pr_info("The CPU has control\n");
+		break;
+	case DCON_SOURCE_DCON:
+	{
+		ktime_t delta_t;
+
+		pr_info("dcon_source_switch to DCON\n");
+
+		/* Clear DCONLOAD - this implies that the DCON is in control */
+		pdata->set_dconload(0);
+		dcon->load_time = ktime_get();
+
+		wait_event_timeout(dcon->waitq, dcon->switched, HZ/2);
+
+		if (!dcon->switched) {
+			pr_err("Timeout entering DCON mode; expect a screen glitch.\n");
+		} else {
+			/* 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(dcon->irq_time, dcon->load_time);
+			if (dcon->switched && ktime_to_ns(delta_t)
+			    < NSEC_PER_MSEC * 20) {
+				pr_err("missed loading, retrying\n");
+				pdata->set_dconload(1);
+				mdelay(41);
+				pdata->set_dconload(0);
+				dcon->load_time = ktime_get();
+				mdelay(41);
+			}
+		}
+
+		dcon_blank_fb(dcon, true);
+		pr_info("The DCON has control\n");
+		break;
+	}
+	default:
+		BUG();
+	}
+
+	dcon->curr_src = source;
+}
+
+static void dcon_set_source(struct dcon_priv *dcon, int arg)
+{
+	if (dcon->pending_src == arg)
+		return;
+
+	dcon->pending_src = arg;
+
+	if (dcon->curr_src != arg)
+		schedule_work(&dcon->switch_source);
+}
+
+static void dcon_set_source_sync(struct dcon_priv *dcon, int arg)
+{
+	dcon_set_source(dcon, arg);
+	flush_scheduled_work();
+}
+
+static ssize_t dcon_mode_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	struct dcon_priv *dcon = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%4.4X\n", dcon->disp_mode);
+}
+
+static ssize_t dcon_sleep_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	struct dcon_priv *dcon = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", dcon->asleep);
+}
+
+static ssize_t dcon_freeze_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	struct dcon_priv *dcon = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", dcon->curr_src == DCON_SOURCE_DCON ? 1 : 0);
+}
+
+static ssize_t dcon_mono_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	struct dcon_priv *dcon = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", dcon->mono);
+}
+
+static ssize_t dcon_resumeline_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%d\n", resumeline);
+}
+
+static ssize_t dcon_mono_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;
+
+	dcon_set_mono_mode(dev_get_drvdata(dev), enable_mono ? true : false);
+
+	return count;
+}
+
+static ssize_t dcon_freeze_store(struct device *dev,
+	struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct dcon_priv *dcon = dev_get_drvdata(dev);
+	unsigned long output;
+	int ret;
+
+	ret = kstrtoul(buf, 10, &output);
+	if (ret)
+		return ret;
+
+	pr_info("dcon_freeze_store: %lu\n", output);
+
+	switch (output) {
+	case 0:
+		dcon_set_source(dcon, DCON_SOURCE_CPU);
+		break;
+	case 1:
+		dcon_set_source_sync(dcon, DCON_SOURCE_DCON);
+		break;
+	case 2:  /* normally unused */
+		dcon_set_source(dcon, DCON_SOURCE_DCON);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return count;
+}
+
+static ssize_t dcon_resumeline_store(struct device *dev,
+	struct device_attribute *attr, const char *buf, size_t count)
+{
+	unsigned short rl;
+	int rc;
+
+	rc = kstrtou16(buf, 10, &rl);
+	if (rc)
+		return rc;
+
+	resumeline = rl;
+	dcon_write(dev_get_drvdata(dev), DCON_REG_SCAN_INT, resumeline);
+
+	return count;
+}
+
+static ssize_t dcon_sleep_store(struct device *dev,
+	struct device_attribute *attr, const char *buf, size_t count)
+{
+	unsigned long output;
+	int ret;
+
+	ret = kstrtoul(buf, 10, &output);
+	if (ret)
+		return ret;
+
+	dcon_sleep(dev_get_drvdata(dev), output ? true : false);
+	return count;
+}
+
+static struct device_attribute dcon_device_files[] = {
+	__ATTR(mode, 0444, dcon_mode_show, NULL),
+	__ATTR(sleep, 0644, dcon_sleep_show, dcon_sleep_store),
+	__ATTR(freeze, 0644, dcon_freeze_show, dcon_freeze_store),
+	__ATTR(monochrome, 0644, dcon_mono_show, dcon_mono_store),
+	__ATTR(resumeline, 0644, dcon_resumeline_show, dcon_resumeline_store),
+};
+
+static int dcon_bl_update(struct backlight_device *dev)
+{
+	struct dcon_priv *dcon = bl_get_data(dev);
+	u8 level = dev->props.brightness & 0x0F;
+
+	if (dev->props.power != FB_BLANK_UNBLANK)
+		level = 0;
+
+	if (level != dcon->bl_val)
+		dcon_set_backlight(dcon, level);
+
+	/* power down the DCON when the screen is blanked */
+	if (!dcon->ignore_fb_events)
+		dcon_sleep(dcon, !!(dev->props.state & BL_CORE_FBBLANK));
+
+	return 0;
+}
+
+static int dcon_bl_get(struct backlight_device *dev)
+{
+	struct dcon_priv *dcon = bl_get_data(dev);
+
+	return dcon->bl_val;
+}
+
+static const struct backlight_ops dcon_bl_ops = {
+	.update_status = dcon_bl_update,
+	.get_brightness = dcon_bl_get,
+};
+
+static struct backlight_properties dcon_bl_props = {
+	.max_brightness = 15,
+	.type = BACKLIGHT_RAW,
+	.power = FB_BLANK_UNBLANK,
+};
+
+static int dcon_reboot_notify(struct notifier_block *nb,
+			      unsigned long foo, void *bar)
+{
+	struct dcon_priv *dcon = container_of(nb, struct dcon_priv, reboot_nb);
+
+	if (!dcon || !dcon->client)
+		return NOTIFY_DONE;
+
+	/* Turn off the DCON. Entirely. */
+	dcon_write(dcon, DCON_REG_MODE, 0x39);
+	dcon_write(dcon, DCON_REG_MODE, 0x32);
+	return NOTIFY_DONE;
+}
+
+static int unfreeze_on_panic(struct notifier_block *nb,
+			     unsigned long e, void *p)
+{
+	pdata->set_dconload(1);
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block dcon_panic_nb = {
+	.notifier_call = unfreeze_on_panic,
+};
+
+static int dcon_detect(struct i2c_client *client, struct i2c_board_info *info)
+{
+	strlcpy(info->type, "olpc_dcon", I2C_NAME_SIZE);
+
+	return 0;
+}
+
+static int dcon_probe(struct i2c_client *client, const struct i2c_device_id *id)
+{
+	struct dcon_priv *dcon;
+	int rc, i, j;
+
+	if (!pdata)
+		return -ENXIO;
+
+	dcon = kzalloc(sizeof(*dcon), GFP_KERNEL);
+	if (!dcon)
+		return -ENOMEM;
+
+	dcon->client = client;
+	init_waitqueue_head(&dcon->waitq);
+	INIT_WORK(&dcon->switch_source, dcon_source_switch);
+	dcon->reboot_nb.notifier_call = dcon_reboot_notify;
+	dcon->reboot_nb.priority = -1;
+
+	i2c_set_clientdata(client, dcon);
+
+	if (num_registered_fb < 1) {
+		dev_err(&client->dev, "DCON driver requires a registered fb\n");
+		rc = -EIO;
+		goto einit;
+	}
+	dcon->fbinfo = registered_fb[0];
+
+	rc = dcon_hw_init(dcon, 1);
+	if (rc)
+		goto einit;
+
+	/* Add the DCON device */
+
+	dcon_device = platform_device_alloc("dcon", -1);
+
+	if (!dcon_device) {
+		pr_err("Unable to create the DCON device\n");
+		rc = -ENOMEM;
+		goto eirq;
+	}
+	rc = platform_device_add(dcon_device);
+	platform_set_drvdata(dcon_device, dcon);
+
+	if (rc) {
+		pr_err("Unable to add the DCON device\n");
+		goto edev;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(dcon_device_files); i++) {
+		rc = device_create_file(&dcon_device->dev,
+					&dcon_device_files[i]);
+		if (rc) {
+			dev_err(&dcon_device->dev, "Cannot create sysfs file\n");
+			goto ecreate;
+		}
+	}
+
+	dcon->bl_val = dcon_read(dcon, DCON_REG_BRIGHT) & 0x0F;
+
+	/* Add the backlight device for the DCON */
+	dcon_bl_props.brightness = dcon->bl_val;
+	dcon->bl_dev = backlight_device_register("dcon-bl", &dcon_device->dev,
+		dcon, &dcon_bl_ops, &dcon_bl_props);
+	if (IS_ERR(dcon->bl_dev)) {
+		dev_err(&client->dev, "cannot register backlight dev (%ld)\n",
+				PTR_ERR(dcon->bl_dev));
+		dcon->bl_dev = NULL;
+	}
+
+	register_reboot_notifier(&dcon->reboot_nb);
+	atomic_notifier_chain_register(&panic_notifier_list, &dcon_panic_nb);
+
+	return 0;
+
+ ecreate:
+	for (j = 0; j < i; j++)
+		device_remove_file(&dcon_device->dev, &dcon_device_files[j]);
+ edev:
+	platform_device_unregister(dcon_device);
+	dcon_device = NULL;
+ eirq:
+	free_irq(DCON_IRQ, dcon);
+ einit:
+	kfree(dcon);
+	return rc;
+}
+
+static int dcon_remove(struct i2c_client *client)
+{
+	struct dcon_priv *dcon = i2c_get_clientdata(client);
+
+	unregister_reboot_notifier(&dcon->reboot_nb);
+	atomic_notifier_chain_unregister(&panic_notifier_list, &dcon_panic_nb);
+
+	free_irq(DCON_IRQ, dcon);
+
+	backlight_device_unregister(dcon->bl_dev);
+
+	if (dcon_device)
+		platform_device_unregister(dcon_device);
+	cancel_work_sync(&dcon->switch_source);
+
+	kfree(dcon);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM
+static int dcon_suspend(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct dcon_priv *dcon = i2c_get_clientdata(client);
+
+	if (!dcon->asleep) {
+		/* Set up the DCON to have the source */
+		dcon_set_source_sync(dcon, DCON_SOURCE_DCON);
+	}
+
+	return 0;
+}
+
+static int dcon_resume(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct dcon_priv *dcon = i2c_get_clientdata(client);
+
+	if (!dcon->asleep) {
+		dcon_bus_stabilize(dcon, 0);
+		dcon_set_source(dcon, DCON_SOURCE_CPU);
+	}
+
+	return 0;
+}
+
+#else
+
+#define dcon_suspend NULL
+#define dcon_resume NULL
+
+#endif /* CONFIG_PM */
+
+irqreturn_t dcon_interrupt(int irq, void *id)
+{
+	struct dcon_priv *dcon = id;
+	u8 status;
+
+	if (pdata->read_status(&status))
+		return IRQ_NONE;
+
+	switch (status & 3) {
+	case 3:
+		pr_debug("DCONLOAD_MISSED interrupt\n");
+		break;
+
+	case 2:	/* switch to DCON mode */
+	case 1: /* switch to CPU mode */
+		dcon->switched = true;
+		dcon->irq_time = ktime_get();
+		wake_up(&dcon->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 (dcon->curr_src != dcon->pending_src && !dcon->switched) {
+			dcon->switched = true;
+			dcon->irq_time = ktime_get();
+			wake_up(&dcon->waitq);
+			pr_debug("switching w/ status 0/0\n");
+		} else {
+			pr_debug("scanline interrupt w/CPU\n");
+		}
+	}
+
+	return IRQ_HANDLED;
+}
+
+static const struct dev_pm_ops dcon_pm_ops = {
+	.suspend = dcon_suspend,
+	.resume = dcon_resume,
+};
+
+static const struct i2c_device_id dcon_idtable[] = {
+	{ "olpc_dcon",  0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, dcon_idtable);
+
+static struct i2c_driver dcon_driver = {
+	.driver = {
+		.name	= "olpc_dcon",
+		.pm = &dcon_pm_ops,
+	},
+	.class = I2C_CLASS_DDC | I2C_CLASS_HWMON,
+	.id_table = dcon_idtable,
+	.probe = dcon_probe,
+	.remove = dcon_remove,
+	.detect = dcon_detect,
+	.address_list = normal_i2c,
+};
+
+static int __init olpc_dcon_init(void)
+{
+#ifdef CONFIG_FB_OLPC_DCON_1_5
+	/* XO-1.5 */
+	if (olpc_board_at_least(olpc_board(0xd0)))
+		pdata = &dcon_pdata_xo_1_5;
+#endif
+#ifdef CONFIG_FB_OLPC_DCON_1
+	if (!pdata)
+		pdata = &dcon_pdata_xo_1;
+#endif
+
+	return i2c_add_driver(&dcon_driver);
+}
+
+static void __exit olpc_dcon_exit(void)
+{
+	i2c_del_driver(&dcon_driver);
+}
+
+module_init(olpc_dcon_init);
+module_exit(olpc_dcon_exit);
+
+MODULE_LICENSE("GPL");
diff --git a/drivers/staging/olpc_dcon/olpc_dcon.h b/drivers/staging/olpc_dcon/olpc_dcon.h
new file mode 100644
index 000000000000..215e7ec4dea2
--- /dev/null
+++ b/drivers/staging/olpc_dcon/olpc_dcon.h
@@ -0,0 +1,111 @@
+#ifndef OLPC_DCON_H_
+#define OLPC_DCON_H_
+
+#include <linux/notifier.h>
+#include <linux/workqueue.h>
+
+/* DCON registers */
+
+#define DCON_REG_ID		 0
+#define DCON_REG_MODE		 1
+
+#define MODE_PASSTHRU	(1<<0)
+#define MODE_SLEEP	(1<<1)
+#define MODE_SLEEP_AUTO	(1<<2)
+#define MODE_BL_ENABLE	(1<<3)
+#define MODE_BLANK	(1<<4)
+#define MODE_CSWIZZLE	(1<<5)
+#define MODE_COL_AA	(1<<6)
+#define MODE_MONO_LUMA	(1<<7)
+#define MODE_SCAN_INT	(1<<8)
+#define MODE_CLOCKDIV	(1<<9)
+#define MODE_DEBUG	(1<<14)
+#define MODE_SELFTEST	(1<<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	(1<<0)
+/* Memory controller power down function */
+#define MEM_POWER_DOWN		(1<<8)
+/* Memory controller software reset */
+#define MEM_SOFT_RESET		(1<<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
+
+/* Interrupt */
+#define DCON_IRQ                6
+
+struct dcon_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;
+
+	/* 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;
+	bool asleep;
+	/* This get set while controlling fb blank state from the driver */
+	bool ignore_fb_events;
+};
+
+struct dcon_platform_data {
+	int (*init)(struct dcon_priv *);
+	void (*bus_stabilize_wiggle)(void);
+	void (*set_dconload)(int);
+	int (*read_status)(u8 *);
+};
+
+#include <linux/interrupt.h>
+
+irqreturn_t dcon_interrupt(int irq, void *id);
+
+#ifdef CONFIG_FB_OLPC_DCON_1
+extern struct dcon_platform_data dcon_pdata_xo_1;
+#endif
+
+#ifdef CONFIG_FB_OLPC_DCON_1_5
+extern struct dcon_platform_data dcon_pdata_xo_1_5;
+#endif
+
+#endif
diff --git a/drivers/staging/olpc_dcon/olpc_dcon_xo_1.c b/drivers/staging/olpc_dcon/olpc_dcon_xo_1.c
new file mode 100644
index 000000000000..0c5a10c69401
--- /dev/null
+++ b/drivers/staging/olpc_dcon/olpc_dcon_xo_1.c
@@ -0,0 +1,205 @@
+/*
+ * Mainly by David Woodhouse, somewhat modified by Jordan Crouse
+ *
+ * Copyright © 2006-2007  Red Hat, Inc.
+ * Copyright © 2006-2007  Advanced Micro Devices, Inc.
+ * Copyright © 2009       VIA Technology, Inc.
+ * Copyright (c) 2010  Andres Salomon <dilinger@queued.net>
+ *
+ * This program is free software.  You can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/cs5535.h>
+#include <linux/gpio.h>
+#include <linux/delay.h>
+#include <asm/olpc.h>
+
+#include "olpc_dcon.h"
+
+static int dcon_init_xo_1(struct dcon_priv *dcon)
+{
+	unsigned char lob;
+
+	if (gpio_request(OLPC_GPIO_DCON_STAT0, "OLPC-DCON")) {
+		pr_err("failed to request STAT0 GPIO\n");
+		return -EIO;
+	}
+	if (gpio_request(OLPC_GPIO_DCON_STAT1, "OLPC-DCON")) {
+		pr_err("failed to request STAT1 GPIO\n");
+		goto err_gp_stat1;
+	}
+	if (gpio_request(OLPC_GPIO_DCON_IRQ, "OLPC-DCON")) {
+		pr_err("failed to request IRQ GPIO\n");
+		goto err_gp_irq;
+	}
+	if (gpio_request(OLPC_GPIO_DCON_LOAD, "OLPC-DCON")) {
+		pr_err("failed to request LOAD GPIO\n");
+		goto err_gp_load;
+	}
+	if (gpio_request(OLPC_GPIO_DCON_BLANK, "OLPC-DCON")) {
+		pr_err("failed to request BLANK GPIO\n");
+		goto err_gp_blank;
+	}
+
+	/* Turn off the event enable for GPIO7 just to be safe */
+	cs5535_gpio_clear(OLPC_GPIO_DCON_IRQ, GPIO_EVENTS_ENABLE);
+
+	/*
+	 * Determine the current state by reading the GPIO bit; earlier
+	 * stages of the boot process have established the state.
+	 *
+	 * Note that we read GPIO_OUTPUT_VAL rather than GPIO_READ_BACK here;
+	 * this is because OFW will disable input for the pin and set a value..
+	 * READ_BACK will only contain a valid value if input is enabled and
+	 * then a value is set.  So, future readings of the pin can use
+	 * READ_BACK, but the first one cannot.  Awesome, huh?
+	 */
+	dcon->curr_src = cs5535_gpio_isset(OLPC_GPIO_DCON_LOAD, GPIO_OUTPUT_VAL)
+		? DCON_SOURCE_CPU
+		: DCON_SOURCE_DCON;
+	dcon->pending_src = dcon->curr_src;
+
+	/* Set the directions for the GPIO pins */
+	gpio_direction_input(OLPC_GPIO_DCON_STAT0);
+	gpio_direction_input(OLPC_GPIO_DCON_STAT1);
+	gpio_direction_input(OLPC_GPIO_DCON_IRQ);
+	gpio_direction_input(OLPC_GPIO_DCON_BLANK);
+	gpio_direction_output(OLPC_GPIO_DCON_LOAD,
+			dcon->curr_src == DCON_SOURCE_CPU);
+
+	/* Set up the interrupt mappings */
+
+	/* Set the IRQ to pair 2 */
+	cs5535_gpio_setup_event(OLPC_GPIO_DCON_IRQ, 2, 0);
+
+	/* Enable group 2 to trigger the DCON interrupt */
+	cs5535_gpio_set_irq(2, DCON_IRQ);
+
+	/* Select edge level for interrupt (in PIC) */
+	lob = inb(0x4d0);
+	lob &= ~(1 << DCON_IRQ);
+	outb(lob, 0x4d0);
+
+	/* Register the interrupt handler */
+	if (request_irq(DCON_IRQ, &dcon_interrupt, 0, "DCON", dcon)) {
+		pr_err("failed to request DCON's irq\n");
+		goto err_req_irq;
+	}
+
+	/* Clear INV_EN for GPIO7 (DCONIRQ) */
+	cs5535_gpio_clear(OLPC_GPIO_DCON_IRQ, GPIO_INPUT_INVERT);
+
+	/* Enable filter for GPIO12 (DCONBLANK) */
+	cs5535_gpio_set(OLPC_GPIO_DCON_BLANK, GPIO_INPUT_FILTER);
+
+	/* Disable filter for GPIO7 */
+	cs5535_gpio_clear(OLPC_GPIO_DCON_IRQ, GPIO_INPUT_FILTER);
+
+	/* Disable event counter for GPIO7 (DCONIRQ) and GPIO12 (DCONBLANK) */
+	cs5535_gpio_clear(OLPC_GPIO_DCON_IRQ, GPIO_INPUT_EVENT_COUNT);
+	cs5535_gpio_clear(OLPC_GPIO_DCON_BLANK, GPIO_INPUT_EVENT_COUNT);
+
+	/* Add GPIO12 to the Filter Event Pair #7 */
+	cs5535_gpio_set(OLPC_GPIO_DCON_BLANK, GPIO_FE7_SEL);
+
+	/* Turn off negative Edge Enable for GPIO12 */
+	cs5535_gpio_clear(OLPC_GPIO_DCON_BLANK, GPIO_NEGATIVE_EDGE_EN);
+
+	/* Enable negative Edge Enable for GPIO7 */
+	cs5535_gpio_set(OLPC_GPIO_DCON_IRQ, GPIO_NEGATIVE_EDGE_EN);
+
+	/* Zero the filter amount for Filter Event Pair #7 */
+	cs5535_gpio_set(0, GPIO_FLTR7_AMOUNT);
+
+	/* Clear the negative edge status for GPIO7 and GPIO12 */
+	cs5535_gpio_set(OLPC_GPIO_DCON_IRQ, GPIO_NEGATIVE_EDGE_STS);
+	cs5535_gpio_set(OLPC_GPIO_DCON_BLANK, GPIO_NEGATIVE_EDGE_STS);
+
+	/* FIXME:  Clear the positive status as well, just to be sure */
+	cs5535_gpio_set(OLPC_GPIO_DCON_IRQ, GPIO_POSITIVE_EDGE_STS);
+	cs5535_gpio_set(OLPC_GPIO_DCON_BLANK, GPIO_POSITIVE_EDGE_STS);
+
+	/* Enable events for GPIO7 (DCONIRQ) and GPIO12 (DCONBLANK) */
+	cs5535_gpio_set(OLPC_GPIO_DCON_IRQ, GPIO_EVENTS_ENABLE);
+	cs5535_gpio_set(OLPC_GPIO_DCON_BLANK, GPIO_EVENTS_ENABLE);
+
+	return 0;
+
+err_req_irq:
+	gpio_free(OLPC_GPIO_DCON_BLANK);
+err_gp_blank:
+	gpio_free(OLPC_GPIO_DCON_LOAD);
+err_gp_load:
+	gpio_free(OLPC_GPIO_DCON_IRQ);
+err_gp_irq:
+	gpio_free(OLPC_GPIO_DCON_STAT1);
+err_gp_stat1:
+	gpio_free(OLPC_GPIO_DCON_STAT0);
+	return -EIO;
+}
+
+static void dcon_wiggle_xo_1(void)
+{
+	int x;
+
+	/*
+	 * According to HiMax, when powering the DCON up we should hold
+	 * SMB_DATA high for 8 SMB_CLK cycles.  This will force the DCON
+	 * state machine to reset to a (sane) initial state.  Mitch Bradley
+	 * did some testing and discovered that holding for 16 SMB_CLK cycles
+	 * worked a lot more reliably, so that's what we do here.
+	 *
+	 * According to the cs5536 spec, to set GPIO14 to SMB_CLK we must
+	 * simultaneously set AUX1 IN/OUT to GPIO14; ditto for SMB_DATA and
+	 * GPIO15.
+	 */
+	cs5535_gpio_set(OLPC_GPIO_SMB_CLK, GPIO_OUTPUT_VAL);
+	cs5535_gpio_set(OLPC_GPIO_SMB_DATA, GPIO_OUTPUT_VAL);
+	cs5535_gpio_set(OLPC_GPIO_SMB_CLK, GPIO_OUTPUT_ENABLE);
+	cs5535_gpio_set(OLPC_GPIO_SMB_DATA, GPIO_OUTPUT_ENABLE);
+	cs5535_gpio_clear(OLPC_GPIO_SMB_CLK, GPIO_OUTPUT_AUX1);
+	cs5535_gpio_clear(OLPC_GPIO_SMB_DATA, GPIO_OUTPUT_AUX1);
+	cs5535_gpio_clear(OLPC_GPIO_SMB_CLK, GPIO_OUTPUT_AUX2);
+	cs5535_gpio_clear(OLPC_GPIO_SMB_DATA, GPIO_OUTPUT_AUX2);
+	cs5535_gpio_clear(OLPC_GPIO_SMB_CLK, GPIO_INPUT_AUX1);
+	cs5535_gpio_clear(OLPC_GPIO_SMB_DATA, GPIO_INPUT_AUX1);
+
+	for (x = 0; x < 16; x++) {
+		udelay(5);
+		cs5535_gpio_clear(OLPC_GPIO_SMB_CLK, GPIO_OUTPUT_VAL);
+		udelay(5);
+		cs5535_gpio_set(OLPC_GPIO_SMB_CLK, GPIO_OUTPUT_VAL);
+	}
+	udelay(5);
+	cs5535_gpio_set(OLPC_GPIO_SMB_CLK, GPIO_OUTPUT_AUX1);
+	cs5535_gpio_set(OLPC_GPIO_SMB_DATA, GPIO_OUTPUT_AUX1);
+	cs5535_gpio_set(OLPC_GPIO_SMB_CLK, GPIO_INPUT_AUX1);
+	cs5535_gpio_set(OLPC_GPIO_SMB_DATA, GPIO_INPUT_AUX1);
+}
+
+static void dcon_set_dconload_1(int val)
+{
+	gpio_set_value(OLPC_GPIO_DCON_LOAD, val);
+}
+
+static int dcon_read_status_xo_1(u8 *status)
+{
+	*status = gpio_get_value(OLPC_GPIO_DCON_STAT0);
+	*status |= gpio_get_value(OLPC_GPIO_DCON_STAT1) << 1;
+
+	/* Clear the negative edge status for GPIO7 */
+	cs5535_gpio_set(OLPC_GPIO_DCON_IRQ, GPIO_NEGATIVE_EDGE_STS);
+
+	return 0;
+}
+
+struct dcon_platform_data dcon_pdata_xo_1 = {
+	.init = dcon_init_xo_1,
+	.bus_stabilize_wiggle = dcon_wiggle_xo_1,
+	.set_dconload = dcon_set_dconload_1,
+	.read_status = dcon_read_status_xo_1,
+};
diff --git a/drivers/staging/olpc_dcon/olpc_dcon_xo_1_5.c b/drivers/staging/olpc_dcon/olpc_dcon_xo_1_5.c
new file mode 100644
index 000000000000..6a4d379c16a3
--- /dev/null
+++ b/drivers/staging/olpc_dcon/olpc_dcon_xo_1_5.c
@@ -0,0 +1,161 @@
+/*
+ * Copyright (c) 2009,2010       One Laptop per Child
+ *
+ * This program is free software.  You can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/acpi.h>
+#include <linux/delay.h>
+#include <linux/gpio.h>
+#include <asm/olpc.h>
+
+/* TODO: this eventually belongs in linux/vx855.h */
+#define NR_VX855_GPI    14
+#define NR_VX855_GPO    13
+#define NR_VX855_GPIO   15
+
+#define VX855_GPI(n)    (n)
+#define VX855_GPO(n)    (NR_VX855_GPI + (n))
+#define VX855_GPIO(n)   (NR_VX855_GPI + NR_VX855_GPO + (n))
+
+#include "olpc_dcon.h"
+
+/* Hardware setup on the XO 1.5:
+ *	DCONLOAD connects to VX855_GPIO1 (not SMBCK2)
+ *	DCONBLANK connects to VX855_GPIO8 (not SSPICLK)  unused in driver
+ *	DCONSTAT0 connects to VX855_GPI10 (not SSPISDI)
+ *	DCONSTAT1 connects to VX855_GPI11 (not nSSPISS)
+ *	DCONIRQ connects to VX855_GPIO12
+ *	DCONSMBDATA connects to VX855 graphics CRTSPD
+ *	DCONSMBCLK connects to VX855 graphics CRTSPCLK
+ */
+
+#define VX855_GENL_PURPOSE_OUTPUT 0x44c /* PMIO_Rx4c-4f */
+#define VX855_GPI_STATUS_CHG 0x450  /* PMIO_Rx50 */
+#define VX855_GPI_SCI_SMI 0x452  /* PMIO_Rx52 */
+#define BIT_GPIO12 0x40
+
+#define PREFIX "OLPC DCON:"
+
+static void dcon_clear_irq(void)
+{
+	/* irq status will appear in PMIO_Rx50[6] (RW1C) on gpio12 */
+	outb(BIT_GPIO12, VX855_GPI_STATUS_CHG);
+}
+
+static int dcon_was_irq(void)
+{
+	u_int8_t tmp;
+
+	/* irq status will appear in PMIO_Rx50[6] on gpio12 */
+	tmp = inb(VX855_GPI_STATUS_CHG);
+	return !!(tmp & BIT_GPIO12);
+
+	return 0;
+}
+
+static int dcon_init_xo_1_5(struct dcon_priv *dcon)
+{
+	unsigned int irq;
+
+	dcon_clear_irq();
+
+	/* set   PMIO_Rx52[6] to enable SCI/SMI on gpio12 */
+	outb(inb(VX855_GPI_SCI_SMI)|BIT_GPIO12, VX855_GPI_SCI_SMI);
+
+	/* Determine the current state of DCONLOAD, likely set by firmware */
+	/* GPIO1 */
+	dcon->curr_src = (inl(VX855_GENL_PURPOSE_OUTPUT) & 0x1000) ?
+			DCON_SOURCE_CPU : DCON_SOURCE_DCON;
+	dcon->pending_src = dcon->curr_src;
+
+	/* we're sharing the IRQ with ACPI */
+	irq = acpi_gbl_FADT.sci_interrupt;
+	if (request_irq(irq, &dcon_interrupt, IRQF_SHARED, "DCON", dcon)) {
+		pr_err("DCON (IRQ%d) allocation failed\n", irq);
+		return 1;
+	}
+
+	return 0;
+}
+
+static void set_i2c_line(int sda, int scl)
+{
+	unsigned char tmp;
+	unsigned int port = 0x26;
+
+	/* FIXME: This directly accesses the CRT GPIO controller !!! */
+	outb(port, 0x3c4);
+	tmp = inb(0x3c5);
+
+	if (scl)
+		tmp |= 0x20;
+	else
+		tmp &= ~0x20;
+
+	if (sda)
+		tmp |= 0x10;
+	else
+		tmp &= ~0x10;
+
+	tmp |= 0x01;
+
+	outb(port, 0x3c4);
+	outb(tmp, 0x3c5);
+}
+
+
+static void dcon_wiggle_xo_1_5(void)
+{
+	int x;
+
+	/*
+	 * According to HiMax, when powering the DCON up we should hold
+	 * SMB_DATA high for 8 SMB_CLK cycles.  This will force the DCON
+	 * state machine to reset to a (sane) initial state.  Mitch Bradley
+	 * did some testing and discovered that holding for 16 SMB_CLK cycles
+	 * worked a lot more reliably, so that's what we do here.
+	 */
+	set_i2c_line(1, 1);
+
+	for (x = 0; x < 16; x++) {
+		udelay(5);
+		set_i2c_line(1, 0);
+		udelay(5);
+		set_i2c_line(1, 1);
+	}
+	udelay(5);
+
+	/* set   PMIO_Rx52[6] to enable SCI/SMI on gpio12 */
+	outb(inb(VX855_GPI_SCI_SMI)|BIT_GPIO12, VX855_GPI_SCI_SMI);
+}
+
+static void dcon_set_dconload_xo_1_5(int val)
+{
+	gpio_set_value(VX855_GPIO(1), val);
+}
+
+static int dcon_read_status_xo_1_5(u8 *status)
+{
+	if (!dcon_was_irq())
+		return -1;
+
+	/* i believe this is the same as "inb(0x44b) & 3" */
+	*status = gpio_get_value(VX855_GPI(10));
+	*status |= gpio_get_value(VX855_GPI(11)) << 1;
+
+	dcon_clear_irq();
+
+	return 0;
+}
+
+struct dcon_platform_data dcon_pdata_xo_1_5 = {
+	.init = dcon_init_xo_1_5,
+	.bus_stabilize_wiggle = dcon_wiggle_xo_1_5,
+	.set_dconload = dcon_set_dconload_xo_1_5,
+	.read_status = dcon_read_status_xo_1_5,
+};