staging: olpc_dcon: add OLPC display controller (DCON) support

This adds DCON support for the OLPC XO.  The DCON is found in XO-1 and
XO-1.5 hardware.  The XO-1 has a CS5536 southbridge, while the XO-1.5
has a Via chipset; the GPIO magic that's necessary to communicate with
the DCON chip is unfortunately different across both platforms.  This
driver supports both.

This driver is in bad state atm, so I'm requesting its inclusion into
staging so it can be cleaned up while staying in the kernel tree.

Original driver by Dave Woodhouse, and modified extensively by
Jordan Crouse, myself, Deepak Saxena, Paul Fox, Daniel Drake, and
probably others that I've missed.
Signed-off-by: Andres Salomon <dilinger@queued.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/Kconfig

@@ -69,6 +69,8 @@ source "drivers/staging/rt2870/Kconfig"
 
 source "drivers/staging/comedi/Kconfig"
 
+source "drivers/staging/olpc_dcon/Kconfig"
+
 source "drivers/staging/asus_oled/Kconfig"
 
 source "drivers/staging/panel/Kconfig"

drivers/staging/Makefile

@@ -18,6 +18,7 @@ obj-$(CONFIG_BRCM80211)		+= brcm80211/
 obj-$(CONFIG_RT2860)		+= rt2860/
 obj-$(CONFIG_RT2870)		+= rt2870/
 obj-$(CONFIG_COMEDI)		+= comedi/
+obj-$(CONFIG_FB_OLPC_DCON)	+= olpc_dcon/
 obj-$(CONFIG_ASUS_OLED)		+= asus_oled/
 obj-$(CONFIG_PANEL)		+= panel/
 obj-$(CONFIG_R8187SE)		+= rtl8187se/

drivers/staging/olpc_dcon/Kconfig

+config FB_OLPC_DCON
+	tristate "One Laptop Per Child Display CONtroller support"
+	depends on OLPC
+	select I2C
+	---help---
+	  Add support for the OLPC XO DCON controller.  This controller is
+	  only available on OLPC platforms.   Unless you have one of these
+	  platforms, you will want to say 'N'.

drivers/staging/olpc_dcon/Makefile

+obj-$(CONFIG_FB_OLPC_DCON)	+= olpc_dcon.o

drivers/staging/olpc_dcon/olpc_dcon.c

+/*
+ * 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.
+ */
+
+
+#include <linux/kernel.h>
+#include <linux/fb.h>
+#include <linux/console.h>
+#include <linux/i2c.h>
+#include <linux/platform_device.h>
+#include <linux/i2c-id.h>
+#include <linux/pci.h>
+#include <linux/vt_kern.h>
+#include <linux/pci_ids.h>
+#include <linux/interrupt.h>
+#include <linux/delay.h>
+#include <linux/backlight.h>
+#include <linux/device.h>
+#include <linux/notifier.h>
+#include <asm/uaccess.h>
+#include <linux/ctype.h>
+#include <linux/reboot.h>
+#include <linux/gpio.h>
+#include <asm/tsc.h>
+#include <asm/olpc.h>
+
+#include "olpc_dcon.h"
+
+/* Module definitions */
+
+static int resumeline = 898;
+module_param(resumeline, int, 0444);
+
+static int noinit;
+module_param(noinit, int, 0444);
+
+/* Default off since it doesn't work on DCON ASIC in B-test OLPC board */
+static int useaa = 1;
+module_param(useaa, int, 0444);
+
+struct dcon_platform_data {
+	int (*init)(void);
+	void (*bus_stabilize_wiggle)(void);
+	void (*set_dconload)(int);
+	int (*read_status)(void);
+};
+
+static struct dcon_platform_data *pdata;
+
+/* I2C structures */
+
+static struct i2c_driver dcon_driver;
+static struct i2c_client *dcon_client;
+
+/* Platform devices */
+static struct platform_device *dcon_device;
+
+/* Backlight device */
+static struct backlight_device *dcon_bl_dev;
+
+static struct fb_info *fbinfo;
+
+/* set this to 1 while controlling fb blank state from this driver */
+static int ignore_fb_events = 0;
+
+/* Current source, initialized at probe time */
+static int dcon_source;
+
+/* Desired source */
+static int dcon_pending;
+
+/* Current output type */
+static int dcon_output = DCON_OUTPUT_COLOR;
+
+/* Current sleep status (not yet implemented) */
+static int dcon_sleep_val = DCON_ACTIVE;
+
+/* Shadow register for the DCON_REG_MODE register */
+static unsigned short dcon_disp_mode;
+
+/* Variables used during switches */
+static int dcon_switched;
+static struct timespec dcon_irq_time;
+static struct timespec dcon_load_time; 
+
+static DECLARE_WAIT_QUEUE_HEAD(dcon_wait_queue);
+
+static unsigned short normal_i2c[] = { 0x0d, I2C_CLIENT_END };
+
+#define dcon_write(reg,val) i2c_smbus_write_word_data(dcon_client,reg,val)
+#define dcon_read(reg) i2c_smbus_read_word_data(dcon_client,reg)
+
+/* The current backlight value - this saves us some smbus traffic */
+static int bl_val = -1;
+
+/* ===== API functions - these are called by a variety of users ==== */
+
+static int dcon_hw_init(struct i2c_client *client, int is_init)
+{
+	uint16_t ver;
+	int rc = 0;
+
+	ver = i2c_smbus_read_word_data(client, DCON_REG_ID);
+	if ((ver >> 8) != 0xDC) {
+		printk(KERN_ERR "olpc-dcon:  DCON ID not 0xDCxx: 0x%04x "
+				"instead.\n", ver);
+		rc = -ENXIO;
+		goto err;
+	}
+
+	if (is_init) {
+		printk(KERN_INFO "olpc-dcon:  Discovered DCON version %x\n",
+				ver & 0xFF);
+		if ((rc = pdata->init()) != 0) {
+			printk(KERN_ERR "olpc-dcon:  Unable to init.\n");
+			goto err;
+		}
+	}
+
+	if (ver < 0xdc02 && !noinit) {
+		/* Initialize the DCON registers */
+
+		/* Start with work-arounds for DCON ASIC */
+		i2c_smbus_write_word_data(client, 0x4b, 0x00cc);
+		i2c_smbus_write_word_data(client, 0x4b, 0x00cc);
+		i2c_smbus_write_word_data(client, 0x4b, 0x00cc);
+		i2c_smbus_write_word_data(client, 0x0b, 0x007a);
+		i2c_smbus_write_word_data(client, 0x36, 0x025c);
+		i2c_smbus_write_word_data(client, 0x37, 0x025e);
+		
+		/* Initialise SDRAM */
+
+		i2c_smbus_write_word_data(client, 0x3b, 0x002b);
+		i2c_smbus_write_word_data(client, 0x41, 0x0101);
+		i2c_smbus_write_word_data(client, 0x42, 0x0101);
+	}
+	else if (!noinit) {
+		/* SDRAM setup/hold time */
+		i2c_smbus_write_word_data(client, 0x3a, 0xc040);
+		i2c_smbus_write_word_data(client, 0x41, 0x0000);
+		i2c_smbus_write_word_data(client, 0x41, 0x0101);
+		i2c_smbus_write_word_data(client, 0x42, 0x0101);
+	}
+
+	/* Colour swizzle, AA, no passthrough, backlight */
+	if (is_init) {
+		dcon_disp_mode = MODE_PASSTHRU | MODE_BL_ENABLE | MODE_CSWIZZLE;
+		if (useaa)
+			dcon_disp_mode |= MODE_COL_AA;
+	}
+	i2c_smbus_write_word_data(client, DCON_REG_MODE, dcon_disp_mode);
+
+
+	/* Set the scanline to interrupt on during resume */
+	i2c_smbus_write_word_data(client, 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 i2c_client *client, int is_powered_down)
+{
+	unsigned long timeout;
+	int x;
+
+power_up:
+	if (is_powered_down) {
+		x = 1;
+		if ((x = olpc_ec_cmd(0x26, (unsigned char *) &x, 1, NULL, 0))) {
+			printk(KERN_WARNING "olpc-dcon:  unable to force dcon "
+					"to power up: %d!\n", x);
+			return x;
+		}
+		msleep(10); /* we'll be conservative */
+	}
+	
+	pdata->bus_stabilize_wiggle();
+
+	for (x = -1, timeout = 50; timeout && x < 0; timeout--) {
+		msleep(1);
+		x = dcon_read(DCON_REG_ID);
+	}
+	if (x < 0) {
+		printk(KERN_ERR "olpc-dcon:  unable to stabilize dcon's "
+				"smbus, reasserting power and praying.\n");
+		BUG_ON(olpc_board_at_least(olpc_board(BOARD_XO_1_C2)));
+		x = 0;
+		olpc_ec_cmd(0x26, (unsigned char *) &x, 1, NULL, 0);
+		msleep(100);
+		is_powered_down = 1;
+		goto power_up;	/* argh, stupid hardware.. */
+	}
+
+	if (is_powered_down)
+		return dcon_hw_init(client, 0);
+	return 0;
+}
+
+
+/* Backlight notes - turning off the backlight enable bit in the DCON
+ * doesn't save us any power over just pushing the BL to zero, so we
+ * don't use that bit in this code.
+ */
+
+static int dcon_get_backlight(void)
+{
+	if (dcon_client == NULL)
+		return 0;
+
+	if (bl_val == -1)
+		bl_val = dcon_read(DCON_REG_BRIGHT) & 0x0F;
+
+	return bl_val;
+}
+
+
+static void dcon_set_backlight_hw(int level)
+{
+	bl_val = level & 0x0F;
+	dcon_write(DCON_REG_BRIGHT, bl_val);
+
+	/* Purposely turn off the backlight when we go to level 0 */
+	if (bl_val == 0) {
+		dcon_disp_mode &= ~MODE_BL_ENABLE;
+		dcon_write(DCON_REG_MODE, dcon_disp_mode);
+	} else if (!(dcon_disp_mode & MODE_BL_ENABLE)) {
+		dcon_disp_mode |= MODE_BL_ENABLE;
+		dcon_write(DCON_REG_MODE, dcon_disp_mode);
+	}
+}
+
+static void dcon_set_backlight(int level)
+{
+	if (dcon_client == NULL)
+		return;
+
+	if (bl_val == (level & 0x0F))
+		return;
+
+	dcon_set_backlight_hw(level);
+}
+
+/* Set the output type to either color or mono */
+
+static int dcon_set_output(int arg)
+{
+	if (dcon_output == arg)
+		return 0;
+
+	dcon_output = arg;
+
+	if (arg == DCON_OUTPUT_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;
+		if (useaa)
+			dcon_disp_mode |= MODE_COL_AA;
+	}
+
+	dcon_write(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(int state)
+{
+	int x;
+
+	/* Turn off the backlight and put the DCON to sleep */
+
+	if (state == dcon_sleep_val)
+		return;
+
+	if (!olpc_board_at_least(olpc_board(BOARD_XO_1_C2)))
+		return;
+
+	if (state == DCON_SLEEP) {
+		x = 0;
+		if ((x = olpc_ec_cmd(0x26, (unsigned char *) &x, 1, NULL, 0)))
+			printk(KERN_WARNING "olpc-dcon:  unable to force dcon "
+					"to power down: %d!\n", x);
+		else
+			dcon_sleep_val = state;
+	}
+	else {
+		/* Only re-enable the backlight if the backlight value is set */
+		if (bl_val != 0)
+			dcon_disp_mode |= MODE_BL_ENABLE;
+
+		if ((x=dcon_bus_stabilize(dcon_client, 1)))
+			printk(KERN_WARNING "olpc-dcon:  unable to reinit dcon"
+					" hardware: %d!\n", x);
+		else
+			dcon_sleep_val = state;
+
+		/* Restore backlight */
+		dcon_set_backlight_hw(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.
+ */
+void dcon_load_holdoff(void)
+{
+	struct timespec delta_t, now;
+	while(1) {
+		getnstimeofday(&now);
+		delta_t = timespec_sub(now, dcon_load_time);
+		if (delta_t.tv_sec != 0 ||
+			delta_t.tv_nsec > NSEC_PER_MSEC * 20) {
+			break;
+		}
+		mdelay(4);
+	}
+}
+/* Set the source of the display (CPU or DCON) */
+
+static void dcon_source_switch(struct work_struct *work)
+{
+	DECLARE_WAITQUEUE(wait, current);
+	int source = dcon_pending;
+
+	if (dcon_source == source)
+		return;
+
+	dcon_load_holdoff();
+
+	dcon_switched = 0;
+
+	switch (source) {
+	case DCON_SOURCE_CPU:
+		printk("dcon_source_switch to CPU\n");
+		/* Enable the scanline interrupt bit */
+		if (dcon_write(DCON_REG_MODE, dcon_disp_mode | MODE_SCAN_INT))
+			printk(KERN_ERR "olpc-dcon:  couldn't enable scanline interrupt!\n");
+		else {
+			/* Wait up to one second for the scanline interrupt */
+			wait_event_timeout(dcon_wait_queue, dcon_switched == 1, HZ);
+		}
+
+		if (!dcon_switched)
+			printk(KERN_ERR "olpc-dcon:  Timeout entering CPU mode; expect a screen glitch.\n");
+
+		/* Turn off the scanline interrupt */
+		if (dcon_write(DCON_REG_MODE, dcon_disp_mode))
+			printk(KERN_ERR "olpc-dcon:  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..
+		 */
+		acquire_console_sem();
+		ignore_fb_events = 1;
+		if (fb_blank(fbinfo, FB_BLANK_UNBLANK)) {
+			ignore_fb_events = 0;
+			release_console_sem();
+			printk(KERN_ERR "olpc-dcon:  Failed to enter CPU mode\n");
+			dcon_pending = DCON_SOURCE_DCON;
+			return;
+		}
+		ignore_fb_events = 0;
+		release_console_sem();
+
+		/* And turn off the DCON */
+		pdata->set_dconload(1);
+		getnstimeofday(&dcon_load_time);
+
+		printk(KERN_INFO "olpc-dcon: The CPU has control\n");
+		break;
+	case DCON_SOURCE_DCON:
+	{
+		int t;
+		struct timespec delta_t;
+
+		printk("dcon_source_switch to DCON\n");
+
+		add_wait_queue(&dcon_wait_queue, &wait);
+		set_current_state(TASK_UNINTERRUPTIBLE);
+
+		/* Clear DCONLOAD - this implies that the DCON is in control */
+		pdata->set_dconload(0);
+		getnstimeofday(&dcon_load_time);
+
+		t = schedule_timeout(HZ/2);
+		remove_wait_queue(&dcon_wait_queue, &wait);
+		set_current_state(TASK_RUNNING);
+
+		if (!dcon_switched) {
+			printk(KERN_ERR "olpc-dcon: 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 = timespec_sub(dcon_irq_time, dcon_load_time);
+			if (dcon_switched && delta_t.tv_sec == 0 &&
+					delta_t.tv_nsec < NSEC_PER_MSEC * 20) {
+				printk(KERN_ERR "olpc-dcon: missed loading, retrying\n");
+				pdata->set_dconload(1);
+				mdelay(41);
+				pdata->set_dconload(0);
+				getnstimeofday(&dcon_load_time);
+				mdelay(41);
+			}
+		}
+
+		acquire_console_sem();
+		ignore_fb_events = 1;
+		if (fb_blank(fbinfo, FB_BLANK_POWERDOWN))
+			printk(KERN_ERR "olpc-dcon:  couldn't blank fb!\n");
+		ignore_fb_events = 0;
+		release_console_sem();
+
+		printk(KERN_INFO "olpc-dcon: The DCON has control\n");
+		break;
+	}
+	default:
+		BUG();
+	}
+
+	dcon_source = source;
+}
+
+static DECLARE_WORK(dcon_work, dcon_source_switch);
+
+static void dcon_set_source(int arg)
+{
+	if (dcon_pending == arg)
+		return;
+
+	dcon_pending = arg;
+
+	if ((dcon_source != arg) && !work_pending(&dcon_work))
+		schedule_work(&dcon_work);
+}
+
+static void dcon_set_source_sync(int arg)
+{
+	dcon_set_source(arg);
+	flush_scheduled_work();
+}
+
+static int dconbl_set(struct backlight_device *dev) {
+
+	int level = dev->props.brightness;
+
+	if (dev->props.power != FB_BLANK_UNBLANK)
+		level = 0;
+
+	dcon_set_backlight(level);
+	return 0;
+}
+
+static int dconbl_get(struct backlight_device *dev) {
+	return dcon_get_backlight();
+}
+
+static ssize_t dcon_mode_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%4.4X\n", dcon_disp_mode);
+}
+
+static ssize_t dcon_sleep_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+
+	return sprintf(buf, "%d\n", dcon_sleep_val);
+}
+
+static ssize_t dcon_freeze_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%d\n", dcon_source == DCON_SOURCE_DCON ? 1 : 0);
+}
+
+static ssize_t dcon_output_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%d\n", dcon_output);
+}
+
+static ssize_t dcon_resumeline_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%d\n", resumeline);
+}
+
+static int _strtoul(const char *buf, int len, unsigned int *val)
+{
+
+	char *endp;
+	unsigned int output = simple_strtoul(buf, &endp, 0);
+	int size = endp - buf;
+
+	if (*endp && isspace(*endp))
+		size++;
+
+	if (size != len)
+		return -EINVAL;
+
+	*val = output;
+	return 0;
+}
+
+static ssize_t dcon_output_store(struct device *dev,
+	struct device_attribute *attr, const char *buf, size_t count)
+{
+	int output;
+	int rc = -EINVAL;
+
+	if (_strtoul(buf, count, &output))
+		return -EINVAL;
+
+	if (output == DCON_OUTPUT_COLOR || output == DCON_OUTPUT_MONO) {
+		dcon_set_output(output);
+		rc = count;
+	}
+
+	return rc;
+}
+
+static ssize_t dcon_freeze_store(struct device *dev,
+	struct device_attribute *attr, const char *buf, size_t count)
+{
+	int output;
+
+	if (_strtoul(buf, count, &output))
+		return -EINVAL;
+
+	printk("dcon_freeze_store: %d\n", output);
+
+	switch (output) {
+	case 0:
+		dcon_set_source(DCON_SOURCE_CPU);
+		break;
+	case 1:
+		dcon_set_source_sync(DCON_SOURCE_DCON);
+		break;
+	case 2:  // normally unused
+		dcon_set_source(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)
+{
+	int rl;
+	int rc = -EINVAL;
+
+	if (_strtoul(buf, count, &rl))
+		return rc;
+
+	resumeline = rl;
+	dcon_write(DCON_REG_SCAN_INT, resumeline);
+	rc = count;
+
+	return rc;
+}
+
+static ssize_t dcon_sleep_store(struct device *dev,
+	struct device_attribute *attr, const char *buf, size_t count)
+{
+	int output;
+
+	if (_strtoul(buf, count, &output))
+		return -EINVAL;
+
+	dcon_sleep(output ? DCON_SLEEP : DCON_ACTIVE);
+	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(output, 0644, dcon_output_show, dcon_output_store),
+	__ATTR(resumeline, 0644, dcon_resumeline_show, dcon_resumeline_store),
+};
+
+static struct backlight_ops dcon_bl_ops = {
+	.get_brightness = dconbl_get,
+	.update_status = dconbl_set
+};
+
+
+static int dcon_reboot_notify(struct notifier_block *nb, unsigned long foo, void *bar)
+{
+	if (dcon_client == NULL)
+		return 0;
+
+	/* Turn off the DCON. Entirely. */
+	dcon_write(DCON_REG_MODE, 0x39);
+	dcon_write(DCON_REG_MODE, 0x32);
+	return 0;
+}
+
+static int dcon_conswitch_notify(struct notifier_block *nb,
+				 unsigned long mode, void *dummy)
+{
+	if (mode == CONSOLE_EVENT_SWITCH_TEXT)
+		dcon_sleep(DCON_ACTIVE);
+
+	return 0;
+}
+
+static struct notifier_block dcon_nb = {
+	.notifier_call = dcon_reboot_notify,
+	.priority = -1,
+};
+
+static struct notifier_block dcon_console_nb = {
+	.notifier_call = dcon_conswitch_notify,
+	.priority = -1,
+};
+
+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,
+};
+
+/* when framebuffer sleeps due to external source (e.g. user idle), power down
+ * the DCON. also power up when the framebuffer comes back to life. */
+static int fb_notifier_callback(struct notifier_block *self, unsigned long event, void *data)
+{
+	struct fb_event *evdata = data;
+	int *blank = (int *) evdata->data;
+	if (event != FB_EVENT_BLANK || ignore_fb_events)
+		return 0;
+	dcon_sleep((*blank) ? DCON_SLEEP : DCON_ACTIVE);
+	return 0;
+}
+
+static struct notifier_block fb_nb = {
+	.notifier_call = fb_notifier_callback,
+};
+
+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)
+{
+	int rc, i;
+
+	if (num_registered_fb >= 1)
+		fbinfo = registered_fb[0];
+
+	rc = dcon_hw_init(client, 1);
+	if (rc)
+		goto einit;
+
+	/* Add the DCON device */
+
+	dcon_device = platform_device_alloc("dcon", -1);
+
+	if (dcon_device == NULL) {
+		printk("dcon:  Unable to create the DCON device\n");
+		rc = -ENOMEM;
+		goto eirq;
+	}
+	/* Place holder...*/
+	i2c_set_clientdata(client, dcon_device);
+
+	if ((rc = platform_device_add(dcon_device))) {
+		printk("dcon:  Unable to add the DCON device\n");
+		goto edev;
+	}
+
+	for(i = 0; i < ARRAY_SIZE(dcon_device_files); i++)
+		device_create_file(&dcon_device->dev, &dcon_device_files[i]);
+
+	/* Add the backlight device for the DCON */
+
+	dcon_client = client;
+
+	dcon_bl_dev = backlight_device_register("dcon-bl", &dcon_device->dev,
+		NULL, &dcon_bl_ops, NULL);
+
+	if (IS_ERR(dcon_bl_dev)) {
+		printk("Could not register the backlight device for the DCON (%ld)\n", PTR_ERR(dcon_bl_dev));
+		dcon_bl_dev = NULL;
+	}
+	else {
+		dcon_bl_dev->props.max_brightness = 15;
+		dcon_bl_dev->props.power = FB_BLANK_UNBLANK;
+		dcon_bl_dev->props.brightness = dcon_get_backlight();
+
+		backlight_update_status(dcon_bl_dev);
+	}
+
+	register_reboot_notifier(&dcon_nb);
+	console_event_register(&dcon_console_nb);
+	atomic_notifier_chain_register(&panic_notifier_list, &dcon_panic_nb);
+	fb_register_client(&fb_nb);
+
+	return 0;
+
+ edev:
+	platform_device_unregister(dcon_device);
+	dcon_device = NULL;
+	i2c_set_clientdata(client, NULL);
+ eirq:
+	free_irq(DCON_IRQ, &dcon_driver);
+ einit:
+	return rc;
+}
+
+static int dcon_remove(struct i2c_client *client)
+{
+	dcon_client = NULL;
+
+	fb_unregister_client(&fb_nb);
+	unregister_reboot_notifier(&dcon_nb);
+	console_event_unregister(&dcon_console_nb);
+	atomic_notifier_chain_unregister(&panic_notifier_list, &dcon_panic_nb);
+
+	free_irq(DCON_IRQ, &dcon_driver);
+
+	if (dcon_bl_dev != NULL)
+		backlight_device_unregister(dcon_bl_dev);
+
+	if (dcon_device != NULL)
+		platform_device_unregister(dcon_device);
+	cancel_work_sync(&dcon_work);
+
+	i2c_set_clientdata(client, NULL);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM
+static int dcon_suspend(struct i2c_client *client, pm_message_t state)
+{
+	if (dcon_sleep_val == DCON_ACTIVE) {
+		/* Set up the DCON to have the source */
+		dcon_set_source_sync(DCON_SOURCE_DCON);
+	}
+
+	return 0;
+}
+
+static int dcon_resume(struct i2c_client *client)
+{
+	if (dcon_sleep_val == DCON_ACTIVE) {
+		dcon_bus_stabilize(client, 0);
+		dcon_set_source(DCON_SOURCE_CPU);
+	}
+
+	return 0;
+}
+
+#endif
+
+
+static irqreturn_t dcon_interrupt(int irq, void *id)
+{
+	int status = pdata->read_status();
+
+	if (status == -1)
+		return IRQ_NONE;
+
+	switch (status & 3) {
+	case 3:
+		printk(KERN_DEBUG "olpc-dcon: DCONLOAD_MISSED interrupt\n");
+		break;
+
+	case 2:	/* switch to DCON mode */
+	case 1: /* switch to CPU mode */
+		dcon_switched = 1;
+		getnstimeofday(&dcon_irq_time);
+		wake_up(&dcon_wait_queue);
+		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_source != dcon_pending && !dcon_switched) {
+			dcon_switched = 1;
+			getnstimeofday(&dcon_irq_time);
+			wake_up(&dcon_wait_queue);
+			printk(KERN_DEBUG "olpc-dcon: switching w/ status 0/0\n");
+		} else {
+			printk(KERN_DEBUG "olpc-dcon: scanline interrupt w/CPU\n");
+		}
+	}
+
+	return IRQ_HANDLED;
+}
+
+static 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",
+	},
+	.class = I2C_CLASS_DDC | I2C_CLASS_HWMON,
+	.id_table = dcon_idtable,
+	.probe = dcon_probe,
+	.remove = __devexit_p(dcon_remove),
+	.detect = dcon_detect,
+	.address_list = normal_i2c,
+#ifdef CONFIG_PM
+	.suspend = dcon_suspend,
+	.resume = dcon_resume,
+#endif
+};
+
+#if defined(CONFIG_OLPC_XO_1)
+#include "olpc_dcon_xo_1.c"
+#elif defined(CONFIG_OLPC_XO_1_5)
+#include "olpc_dcon_xo_1_5.c"
+#else
+#error "Trying to build OLPC DCON driver but kernel not configured for XO"
+#endif
+
+static int __init olpc_dcon_init(void)
+{
+#ifdef CONFIG_OLPC_XO_1
+	pdata = &dcon_pdata_xo_1;
+#else
+	pdata = &dcon_pdata_xo_1_5;
+#endif
+
+	i2c_add_driver(&dcon_driver);
+	return 0;
+}
+
+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");

drivers/staging/olpc_dcon/olpc_dcon.h

+#ifndef OLPC_DCON_H_
+#define OLPC_DCON_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		2
+#define DCON_REG_HTOTAL		3
+#define DCON_REG_HSYNC_WIDTH	4
+#define DCON_REG_VRES		5
+#define DCON_REG_VTOTAL		6
+#define DCON_REG_VSYNC_WIDTH	7
+#define DCON_REG_TIMEOUT	8
+#define DCON_REG_SCAN_INT	9
+#define DCON_REG_BRIGHT		10
+
+/* GPIO registers (CS5536) */
+
+#define MSR_LBAR_GPIO		0x5140000C
+
+#define GPIOx_OUT_VAL     0x00
+#define GPIOx_OUT_EN      0x04
+#define GPIOx_IN_EN       0x20
+#define GPIOx_INV_EN      0x24
+#define GPIOx_IN_FLTR_EN  0x28
+#define GPIOx_EVNTCNT_EN  0x2C
+#define GPIOx_READ_BACK   0x30
+#define GPIOx_EVNT_EN     0x38
+#define GPIOx_NEGEDGE_EN  0x44
+#define GPIOx_NEGEDGE_STS 0x4C
+#define GPIO_FLT7_AMNT    0xD8
+#define GPIO_MAP_X        0xE0
+#define GPIO_MAP_Y        0xE4
+#define GPIO_FE7_SEL      0xF7
+
+
+/* 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
+
+/* Output values */
+#define DCON_OUTPUT_COLOR       0
+#define DCON_OUTPUT_MONO        1
+
+/* Sleep values */
+#define DCON_ACTIVE             0
+#define DCON_SLEEP              1
+
+/* Interrupt */
+#define DCON_IRQ                6
+
+#endif

drivers/staging/olpc_dcon/olpc_dcon_xo_1.c

+/*
+ * 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.
+ */
+
+#include <asm/olpc.h>
+
+#include "olpc_dcon.h"
+
+/* Base address of the GPIO registers */
+static unsigned long gpio_base;
+
+/*
+ * List of GPIOs that we care about:
+ * (in)  GPIO12   -- DCONBLANK
+ * (in)  GPIO[56] -- DCONSTAT[01]
+ * (out) GPIO11   -- DCONLOAD
+ */
+
+#define IN_GPIOS ((1<<5) | (1<<6) | (1<<7) | (1<<12))
+#define OUT_GPIOS (1<<11)
+
+static int dcon_init_xo_1(void)
+{
+	unsigned long lo, hi;
+	unsigned char lob;
+
+	rdmsr(MSR_LBAR_GPIO, lo, hi);
+
+	/* Check the mask and whether GPIO is enabled (sanity check) */
+	if (hi != 0x0000f001) {
+		printk(KERN_ERR "GPIO not enabled -- cannot use DCON\n");
+		return -ENODEV;
+	}
+
+	/* Mask off the IO base address */
+	gpio_base = lo & 0x0000ff00;
+
+	/* Turn off the event enable for GPIO7 just to be safe */
+	outl(1 << (16+7), gpio_base + GPIOx_EVNT_EN);
+
+	/* Set the directions for the GPIO pins */
+	outl(OUT_GPIOS | (IN_GPIOS << 16), gpio_base + GPIOx_OUT_EN);
+	outl(IN_GPIOS | (OUT_GPIOS << 16), gpio_base + GPIOx_IN_EN);
+
+	/* Set up the interrupt mappings */
+
+	/* Set the IRQ to pair 2 */
+	geode_gpio_event_irq(OLPC_GPIO_DCON_IRQ, 2);
+
+	/* Enable group 2 to trigger the DCON interrupt */
+	geode_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 interupt handler */
+	if (request_irq(DCON_IRQ, &dcon_interrupt, 0, "DCON", &dcon_driver))
+		return -EIO;
+
+	/* Clear INV_EN for GPIO7 (DCONIRQ) */
+	outl((1<<(16+7)), gpio_base + GPIOx_INV_EN);
+
+	/* Enable filter for GPIO12 (DCONBLANK) */
+	outl(1<<(12), gpio_base + GPIOx_IN_FLTR_EN);
+
+	/* Disable filter for GPIO7 */
+	outl(1<<(16+7), gpio_base + GPIOx_IN_FLTR_EN);
+
+	/* Disable event counter for GPIO7 (DCONIRQ) and GPIO12 (DCONBLANK) */
+
+	outl(1<<(16+7), gpio_base + GPIOx_EVNTCNT_EN);
+	outl(1<<(16+12), gpio_base + GPIOx_EVNTCNT_EN);
+
+	/* Add GPIO12 to the Filter Event Pair #7 */
+	outb(12, gpio_base + GPIO_FE7_SEL);
+
+	/* Turn off negative Edge Enable for GPIO12 */
+	outl(1<<(16+12), gpio_base + GPIOx_NEGEDGE_EN);
+
+	/* Enable negative Edge Enable for GPIO7 */
+	outl(1<<7, gpio_base + GPIOx_NEGEDGE_EN);
+
+	/* Zero the filter amount for Filter Event Pair #7 */
+	outw(0, gpio_base + GPIO_FLT7_AMNT);
+
+	/* Clear the negative edge status for GPIO7 and GPIO12 */
+	outl((1<<7) | (1<<12), gpio_base+0x4c);
+
+	/* FIXME:  Clear the posiitive status as well, just to be sure */
+	outl((1<<7) | (1<<12), gpio_base+0x48);
+
+	/* Enable events for GPIO7 (DCONIRQ) and GPIO12 (DCONBLANK) */
+	outl((1<<(7))|(1<<12), gpio_base + GPIOx_EVNT_EN);
+
+	/* Determine the current state by reading the GPIO bit */
+	/* Earlier stages of the boot process have established the state */
+	dcon_source = inl(gpio_base + GPIOx_OUT_VAL) & (1<<11)
+		? DCON_SOURCE_CPU
+		: DCON_SOURCE_DCON;
+	dcon_pending = dcon_source;
+
+	return 0;
+}
+
+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.
+ 	 */
+	geode_gpio_set(OLPC_GPIO_SMB_CLK|OLPC_GPIO_SMB_DATA, GPIO_OUTPUT_VAL);
+	geode_gpio_set(OLPC_GPIO_SMB_CLK|OLPC_GPIO_SMB_DATA, GPIO_OUTPUT_ENABLE);
+	geode_gpio_clear(OLPC_GPIO_SMB_CLK|OLPC_GPIO_SMB_DATA, GPIO_OUTPUT_AUX1);
+	geode_gpio_clear(OLPC_GPIO_SMB_CLK|OLPC_GPIO_SMB_DATA, GPIO_OUTPUT_AUX2);
+	geode_gpio_clear(OLPC_GPIO_SMB_CLK|OLPC_GPIO_SMB_DATA, GPIO_INPUT_AUX1);
+
+	for (x = 0; x < 16; x++) {
+		udelay(5);
+		geode_gpio_clear(OLPC_GPIO_SMB_CLK, GPIO_OUTPUT_VAL);
+		udelay(5);
+		geode_gpio_set(OLPC_GPIO_SMB_CLK, GPIO_OUTPUT_VAL);
+	}
+	udelay(5);
+	geode_gpio_set(OLPC_GPIO_SMB_CLK|OLPC_GPIO_SMB_DATA, GPIO_OUTPUT_AUX1);
+	geode_gpio_set(OLPC_GPIO_SMB_CLK|OLPC_GPIO_SMB_DATA, GPIO_INPUT_AUX1);
+}
+
+static void dcon_set_dconload_1(int val)
+{
+	if (val)	
+		outl(1<<11, gpio_base + GPIOx_OUT_VAL);
+	else
+		outl(1<<(11 + 16), gpio_base + GPIOx_OUT_VAL);
+}
+
+static int dcon_read_status_xo_1(void)
+{
+	int status = inl(gpio_base + GPIOx_READ_BACK) >> 5;
+	
+	/* Clear the negative edge status for GPIO7 */
+	outl(1 << 7, gpio_base + GPIOx_NEGEDGE_STS);
+
+	return status;
+}
+
+static 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,
+};

drivers/staging/olpc_dcon/olpc_dcon_xo_1_5.c

+/*
+ * 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.
+ */
+
+#include <linux/acpi.h>
+
+/* Hardware setup on the XO 1.5:
+ * 	DCONLOAD connects to
+ *		VX855_GPO12 (not nCR_PWOFF)   (rev A)
+ *		VX855_GPIO1 (not SMBCK2)      (rev B)
+ * 	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 (on B3.  on B2, it goes to
+ *		SMBALRT, which doesn't work.)
+ *	DCONSMBDATA connects to VX855 graphics CRTSPD
+ *	DCONSMBCLK connects to VX855 graphics CRTSPCLK
+ */
+
+#define TEST_B2 0   // define to test B3 paths on a modded B2 board
+
+#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:"
+
+/*
+  there is no support here for DCONIRQ on 1.5 boards earlier than
+  B3.  the issue is that the DCONIRQ signal on earlier boards is
+  routed to SMBALRT, which turns out to to be a level sensitive
+  interrupt.  the DCONIRQ signal is far too short (11usec) to
+  be detected reliably in that case.  including support for
+  DCONIRQ functions no better than none at all.
+*/
+
+static struct dcon_platform_data dcon_pdata_xo_1_5;
+
+static void dcon_clear_irq(void)
+{
+	if (TEST_B2 || olpc_board_at_least(olpc_board(BOARD_XO_1_5_B3))) {
+		// 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;
+
+	if (TEST_B2 || olpc_board_at_least(olpc_board(BOARD_XO_1_5_B3))) {
+		// 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(void)
+{
+	unsigned int irq;
+	u_int8_t tmp;
+	struct pci_dev *pdev;
+	
+	
+	pdev = pci_get_device(PCI_VENDOR_ID_VIA,
+			      PCI_DEVICE_ID_VIA_VX855, NULL);
+	if (!pdev) {
+		printk(KERN_ERR "cannot find VX855 PCI ID\n");
+		return 1;
+	}
+
+	if (olpc_board_at_least(olpc_board(BOARD_XO_1_5_B1))) {
+		pci_read_config_byte(pdev, 0x95, &tmp);
+		pci_write_config_byte(pdev, 0x95, tmp|0x0c);
+	} else {
+		/* Set GPO12 to GPO mode, not nCR_PWOFF */
+		pci_read_config_byte(pdev, 0x9b, &tmp);
+		pci_write_config_byte(pdev, 0x9b, tmp|0x01);
+	}
+
+	/* Set GPIO8 to GPIO mode, not SSPICLK */
+	pci_read_config_byte(pdev, 0xe3, &tmp);
+	pci_write_config_byte(pdev, 0xe3, tmp | 0x04);
+
+	/* Set GPI10/GPI11 to GPI mode, not SSPISDI/SSPISS */
+	pci_read_config_byte(pdev, 0xe4, &tmp);
+	pci_write_config_byte(pdev, 0xe4, tmp|0x08);
+
+	if (TEST_B2 || olpc_board_at_least(olpc_board(BOARD_XO_1_5_B3))) {
+		// clear PMU_RxE1[6] to select SCI on GPIO12
+		// clear PMU_RxE0[6] to choose falling edge
+		pci_read_config_byte(pdev, 0xe1, &tmp);
+		pci_write_config_byte(pdev, 0xe1, tmp & ~BIT_GPIO12);
+		pci_read_config_byte(pdev, 0xe0, &tmp);
+		pci_write_config_byte(pdev, 0xe0, tmp & ~BIT_GPIO12);
+
+		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 */
+	if (olpc_board_at_least(olpc_board(BOARD_XO_1_5_B1))) {
+		// GPIO1
+		dcon_source = (inl(VX855_GENL_PURPOSE_OUTPUT) & 0x1000) ?
+			DCON_SOURCE_CPU : DCON_SOURCE_DCON;
+	} else {
+		// GPO12
+		dcon_source = (inl(VX855_GENL_PURPOSE_OUTPUT) & 0x04000000) ?
+			DCON_SOURCE_CPU : DCON_SOURCE_DCON;
+	}
+	dcon_pending = dcon_source;
+
+	pci_dev_put(pdev);
+
+	/* we're sharing the IRQ with ACPI */
+	irq = acpi_gbl_FADT.sci_interrupt;
+	if (request_irq(irq, &dcon_interrupt, IRQF_SHARED, "DCON", &dcon_driver)) {
+		printk(KERN_ERR PREFIX "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);
+
+	if (TEST_B2 || olpc_board_at_least(olpc_board(BOARD_XO_1_5_B3))) {
+		// 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)
+{
+	if (olpc_board_at_least(olpc_board(BOARD_XO_1_5_B1))) {
+		gpio_set_value(VX855_GPIO(1), val);
+	} else {
+		gpio_set_value(VX855_GPO(12), val);
+	}
+}
+
+static int dcon_read_status_xo_1_5(void) 
+{
+	int 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 status;
+}
+
+static 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,
+};