USB: ehci-dbgp: stability improvements and external re-init

This patch implements several changes:

1) Improve the capability to debug the dbgp driver

   The dbgp_ehci_status() was added in a number of places to report
   the critical ehci registers to diagnose the cause of a failure of
   the ehci-dbgp driver.

2) Capability to survive the host controller initialization

   The dbgp_external_startup(), dbgp_not_safe, and dbgp_phys_port were
   added so as to allow the ehci-dbgp to re-initialize after the ehci
   host controller is reset by the standard host controller driver.
   This same routine is common for the early startup or
   re-initialization.

   This resulted in the need to move some of the initialization code
   out of the __init section because the ehci driver has the
   possibility to be loaded later on as a kernel module.

3) Stability improvements for device initialization

   The device enumeration from 0 to 127 has the possibility to fail
   the first time after a warm reset on some older EHCI debug
   controllers.  The enumeration will be tried up to 3 times to
   account for this failure case.

   The dbg_wait_until_complete() was changed to wait up to 250 ms
   before failing which only comes into play during device
   initialization. The maximum delay will never get hit during the
   course of normal operation of the driver, unless the device got
   unplugged or there was a ehci controller failure, in which case the
   dbgp device driver will shut itself down.

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: dbrownell@users.sourceforge.net
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/early/ehci-dbgp.c

@@ -1,5 +1,19 @@
+/*
+ * Standalone EHCI usb debug driver
+ *
+ * Originally written by:
+ *  Eric W. Biederman" <ebiederm@xmission.com> and
+ *  Yinghai Lu <yhlu.kernel@gmail.com>
+ *
+ * Changes for early/late printk and HW errata:
+ *  Jason Wessel <jason.wessel@windriver.com>
+ *  Copyright (C) 2009 Wind River Systems, Inc.
+ *
+ */
+
 #include <linux/console.h>
 #include <linux/errno.h>
+#include <linux/module.h>
 #include <linux/pci_regs.h>
 #include <linux/pci_ids.h>
 #include <linux/usb/ch9.h>
@@ -9,15 +23,37 @@
 #include <asm/pci-direct.h>
 #include <asm/fixmap.h>
 
-#ifdef DBGP_DEBUG
-# define dbgp_printk printk
-#else
-static inline void dbgp_printk(const char *fmt, ...) { }
-#endif
+/* The code here is intended to talk directly to the EHCI debug port
+ * and does not require that you have any kind of USB host controller
+ * drivers or USB device drivers compiled into the kernel.
+ *
+ * If you make a change to anything in here, the following test cases
+ * need to pass where a USB debug device works in the following
+ * configurations.
+ *
+ * 1. boot args:  earlyprintk=dbgp
+ *     o kernel compiled with # CONFIG_USB_EHCI_HCD is not set
+ *     o kernel compiled with CONFIG_USB_EHCI_HCD=y
+ * 2. boot args: earlyprintk=dbgp,keep
+ *     o kernel compiled with # CONFIG_USB_EHCI_HCD is not set
+ *     o kernel compiled with CONFIG_USB_EHCI_HCD=y
+ * 3. boot args: earlyprintk=dbgp console=ttyUSB0
+ *     o kernel has CONFIG_USB_EHCI_HCD=y and
+ *       CONFIG_USB_SERIAL_DEBUG=y
+ * 4. boot args: earlyprintk=vga,dbgp
+ *     o kernel compiled with # CONFIG_USB_EHCI_HCD is not set
+ *     o kernel compiled with CONFIG_USB_EHCI_HCD=y
+ *
+ * For the 4th configuration you can turn on or off the DBGP_DEBUG
+ * such that you can debug the dbgp device's driver code.
+ */
+
+static int dbgp_phys_port = 1;
 
 static struct ehci_caps __iomem *ehci_caps;
 static struct ehci_regs __iomem *ehci_regs;
 static struct ehci_dbg_port __iomem *ehci_debug;
+static int dbgp_not_safe; /* Cannot use debug device during ehci reset */
 static unsigned int dbgp_endpoint_out;
 
 struct ehci_dev {
@@ -32,6 +68,26 @@ static struct ehci_dev ehci_dev;
 
 #define DBGP_DATA_TOGGLE	0x8800
 
+#ifdef DBGP_DEBUG
+#define dbgp_printk printk
+static void dbgp_ehci_status(char *str)
+{
+	if (!ehci_debug)
+		return;
+	dbgp_printk("dbgp: %s\n", str);
+	dbgp_printk("  Debug control: %08x", readl(&ehci_debug->control));
+	dbgp_printk("  ehci cmd     : %08x", readl(&ehci_regs->command));
+	dbgp_printk("  ehci conf flg: %08x\n",
+		    readl(&ehci_regs->configured_flag));
+	dbgp_printk("  ehci status  : %08x", readl(&ehci_regs->status));
+	dbgp_printk("  ehci portsc  : %08x\n",
+		    readl(&ehci_regs->port_status[dbgp_phys_port - 1]));
+}
+#else
+static inline void dbgp_ehci_status(char *str) { }
+static inline void dbgp_printk(const char *fmt, ...) { }
+#endif
+
 static inline u32 dbgp_pid_update(u32 x, u32 tok)
 {
 	return ((x ^ DBGP_DATA_TOGGLE) & 0xffff00) | (tok & 0xff);
@@ -79,21 +135,23 @@ static inline u32 dbgp_len_update(u32 x, u32 len)
 #define HUB_RESET_TIMEOUT	500
 
 #define DBGP_MAX_PACKET		8
+#define DBGP_TIMEOUT		(250 * 1000)
 
 static int dbgp_wait_until_complete(void)
 {
 	u32 ctrl;
-	int loop = 0x100000;
+	int loop = DBGP_TIMEOUT;
 
 	do {
 		ctrl = readl(&ehci_debug->control);
 		/* Stop when the transaction is finished */
 		if (ctrl & DBGP_DONE)
 			break;
+		udelay(1);
 	} while (--loop > 0);
 
 	if (!loop)
-		return -1;
+		return -DBGP_TIMEOUT;
 
 	/*
 	 * Now that we have observed the completed transaction,
@@ -103,7 +161,7 @@ static int dbgp_wait_until_complete(void)
 	return (ctrl & DBGP_ERROR) ? -DBGP_ERRCODE(ctrl) : DBGP_LEN(ctrl);
 }
 
-static void __init dbgp_mdelay(int ms)
+static inline void dbgp_mdelay(int ms)
 {
 	int i;
 
@@ -130,8 +188,17 @@ retry:
 	pids = readl(&ehci_debug->pids);
 	lpid = DBGP_PID_GET(pids);
 
-	if (ret < 0)
+	if (ret < 0) {
+		/* A -DBGP_TIMEOUT failure here means the device has
+		 * failed, perhaps because it was unplugged, in which
+		 * case we do not want to hang the system so the dbgp
+		 * will be marked as unsafe to use.  EHCI reset is the
+		 * only way to recover if you unplug the dbgp device.
+		 */
+		if (ret == -DBGP_TIMEOUT && !dbgp_not_safe)
+			dbgp_not_safe = 1;
 		return ret;
+	}
 
 	/*
 	 * If the port is getting full or it has dropped data
@@ -149,7 +216,7 @@ retry:
 	return ret;
 }
 
-static void dbgp_set_data(const void *buf, int size)
+static inline void dbgp_set_data(const void *buf, int size)
 {
 	const unsigned char *bytes = buf;
 	u32 lo, hi;
@@ -164,7 +231,7 @@ static void dbgp_set_data(const void *buf, int size)
 	writel(hi, &ehci_debug->data47);
 }
 
-static void __init dbgp_get_data(void *buf, int size)
+static inline void dbgp_get_data(void *buf, int size)
 {
 	unsigned char *bytes = buf;
 	u32 lo, hi;
@@ -208,7 +275,7 @@ static int dbgp_bulk_write(unsigned devnum, unsigned endpoint,
 	return ret;
 }
 
-static int __init dbgp_bulk_read(unsigned devnum, unsigned endpoint, void *data,
+static int dbgp_bulk_read(unsigned devnum, unsigned endpoint, void *data,
 				 int size)
 {
 	u32 pids, addr, ctrl;
@@ -239,7 +306,7 @@ static int __init dbgp_bulk_read(unsigned devnum, unsigned endpoint, void *data,
 	return ret;
 }
 
-static int __init dbgp_control_msg(unsigned devnum, int requesttype,
+static int dbgp_control_msg(unsigned devnum, int requesttype,
 	int request, int value, int index, void *data, int size)
 {
 	u32 pids, addr, ctrl;
@@ -342,13 +409,179 @@ static u32 __init find_dbgp(int ehci_num, u32 *rbus, u32 *rslot, u32 *rfunc)
 	return 0;
 }
 
+static int dbgp_ehci_startup(void)
+{
+	u32 ctrl, cmd, status;
+	int loop;
+
+	/* Claim ownership, but do not enable yet */
+	ctrl = readl(&ehci_debug->control);
+	ctrl |= DBGP_OWNER;
+	ctrl &= ~(DBGP_ENABLED | DBGP_INUSE);
+	writel(ctrl, &ehci_debug->control);
+	udelay(1);
+
+	dbgp_ehci_status("EHCI startup");
+	/* Start the ehci running */
+	cmd = readl(&ehci_regs->command);
+	cmd &= ~(CMD_LRESET | CMD_IAAD | CMD_PSE | CMD_ASE | CMD_RESET);
+	cmd |= CMD_RUN;
+	writel(cmd, &ehci_regs->command);
+
+	/* Ensure everything is routed to the EHCI */
+	writel(FLAG_CF, &ehci_regs->configured_flag);
+
+	/* Wait until the controller is no longer halted */
+	loop = 10;
+	do {
+		status = readl(&ehci_regs->status);
+		if (!(status & STS_HALT))
+			break;
+		udelay(1);
+	} while (--loop > 0);
+
+	if (!loop) {
+		dbgp_printk("ehci can not be started\n");
+		return -ENODEV;
+	}
+	dbgp_printk("ehci started\n");
+	return 0;
+}
+
+static int dbgp_ehci_controller_reset(void)
+{
+	int loop = 250 * 1000;
+	u32 cmd;
+
+	/* Reset the EHCI controller */
+	cmd = readl(&ehci_regs->command);
+	cmd |= CMD_RESET;
+	writel(cmd, &ehci_regs->command);
+	do {
+		cmd = readl(&ehci_regs->command);
+	} while ((cmd & CMD_RESET) && (--loop > 0));
+
+	if (!loop) {
+		dbgp_printk("can not reset ehci\n");
+		return -1;
+	}
+	dbgp_ehci_status("ehci reset done");
+	return 0;
+}
+static int ehci_wait_for_port(int port);
+/* Return 0 on success
+ * Return -ENODEV for any general failure
+ * Return -EIO if wait for port fails
+ */
+int dbgp_external_startup(void)
+{
+	int devnum;
+	struct usb_debug_descriptor dbgp_desc;
+	int ret;
+	u32 ctrl, portsc;
+	int dbg_port = dbgp_phys_port;
+	int tries = 3;
+
+	ret = dbgp_ehci_startup();
+	if (ret)
+		return ret;
+
+	/* Wait for a device to show up in the debug port */
+	ret = ehci_wait_for_port(dbg_port);
+	if (ret < 0) {
+		portsc = readl(&ehci_regs->port_status[dbg_port - 1]);
+		dbgp_printk("No device found in debug port\n");
+		return -EIO;
+	}
+	dbgp_ehci_status("wait for port done");
+
+	/* Enable the debug port */
+	ctrl = readl(&ehci_debug->control);
+	ctrl |= DBGP_CLAIM;
+	writel(ctrl, &ehci_debug->control);
+	ctrl = readl(&ehci_debug->control);
+	if ((ctrl & DBGP_CLAIM) != DBGP_CLAIM) {
+		dbgp_printk("No device in debug port\n");
+		writel(ctrl & ~DBGP_CLAIM, &ehci_debug->control);
+		return -ENODEV;
+	}
+	dbgp_ehci_status("debug ported enabled");
+
+	/* Completely transfer the debug device to the debug controller */
+	portsc = readl(&ehci_regs->port_status[dbg_port - 1]);
+	portsc &= ~PORT_PE;
+	writel(portsc, &ehci_regs->port_status[dbg_port - 1]);
+
+	dbgp_mdelay(100);
+
+try_again:
+	/* Find the debug device and make it device number 127 */
+	for (devnum = 0; devnum <= 127; devnum++) {
+		ret = dbgp_control_msg(devnum,
+			USB_DIR_IN | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
+			USB_REQ_GET_DESCRIPTOR, (USB_DT_DEBUG << 8), 0,
+			&dbgp_desc, sizeof(dbgp_desc));
+		if (ret > 0)
+			break;
+	}
+	if (devnum > 127) {
+		dbgp_printk("Could not find attached debug device\n");
+		goto err;
+	}
+	if (ret < 0) {
+		dbgp_printk("Attached device is not a debug device\n");
+		goto err;
+	}
+	dbgp_endpoint_out = dbgp_desc.bDebugOutEndpoint;
+
+	/* Move the device to 127 if it isn't already there */
+	if (devnum != USB_DEBUG_DEVNUM) {
+		ret = dbgp_control_msg(devnum,
+			USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
+			USB_REQ_SET_ADDRESS, USB_DEBUG_DEVNUM, 0, NULL, 0);
+		if (ret < 0) {
+			dbgp_printk("Could not move attached device to %d\n",
+				USB_DEBUG_DEVNUM);
+			goto err;
+		}
+		devnum = USB_DEBUG_DEVNUM;
+		dbgp_printk("debug device renamed to 127\n");
+	}
+
+	/* Enable the debug interface */
+	ret = dbgp_control_msg(USB_DEBUG_DEVNUM,
+		USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
+		USB_REQ_SET_FEATURE, USB_DEVICE_DEBUG_MODE, 0, NULL, 0);
+	if (ret < 0) {
+		dbgp_printk(" Could not enable the debug device\n");
+		goto err;
+	}
+	dbgp_printk("debug interface enabled\n");
+	/* Perform a small write to get the even/odd data state in sync
+	 */
+	ret = dbgp_bulk_write(USB_DEBUG_DEVNUM, dbgp_endpoint_out, " ", 1);
+	if (ret < 0) {
+		dbgp_printk("dbgp_bulk_write failed: %d\n", ret);
+		goto err;
+	}
+	dbgp_printk("small write doned\n");
+	dbgp_not_safe = 0;
+
+	return 0;
+err:
+	if (tries--)
+		goto try_again;
+	return -ENODEV;
+}
+EXPORT_SYMBOL_GPL(dbgp_external_startup);
+
 static int __init ehci_reset_port(int port)
 {
 	u32 portsc;
 	u32 delay_time, delay;
 	int loop;
 
-	dbgp_printk("ehci_reset_port %i\n", port);
+	dbgp_ehci_status("reset port");
 	/* Reset the usb debug port */
 	portsc = readl(&ehci_regs->port_status[port - 1]);
 	portsc &= ~PORT_PE;
@@ -388,7 +621,7 @@ static int __init ehci_reset_port(int port)
 	return -EBUSY;
 }
 
-static int __init ehci_wait_for_port(int port)
+static int ehci_wait_for_port(int port)
 {
 	u32 status;
 	int ret, reps;
@@ -487,12 +720,9 @@ static void __init early_ehci_bios_handoff(void)
 
 static int __init ehci_setup(void)
 {
-	struct usb_debug_descriptor dbgp_desc;
-	u32 cmd, ctrl, status, portsc, hcs_params;
+	u32 ctrl, portsc, hcs_params;
 	u32 debug_port, new_debug_port = 0, n_ports;
-	u32  devnum;
 	int ret, i;
-	int loop;
 	int port_map_tried;
 	int playtimes = 3;
 
@@ -505,10 +735,12 @@ try_next_port:
 
 	hcs_params = readl(&ehci_caps->hcs_params);
 	debug_port = HCS_DEBUG_PORT(hcs_params);
+	dbgp_phys_port = debug_port;
 	n_ports    = HCS_N_PORTS(hcs_params);
 
 	dbgp_printk("debug_port: %d\n", debug_port);
 	dbgp_printk("n_ports:    %d\n", n_ports);
+	dbgp_ehci_status("");
 
 	for (i = 1; i <= n_ports; i++) {
 		portsc = readl(&ehci_regs->port_status[i-1]);
@@ -523,138 +755,27 @@ try_next_port:
 		return -1;
 	}
 
-	loop = 250 * 1000;
-	/* Reset the EHCI controller */
-	cmd = readl(&ehci_regs->command);
-	cmd |= CMD_RESET;
-	writel(cmd, &ehci_regs->command);
-	do {
-		cmd = readl(&ehci_regs->command);
-	} while ((cmd & CMD_RESET) && (--loop > 0));
-
-	if (!loop) {
-		dbgp_printk("can not reset ehci\n");
-		return -1;
-	}
-	dbgp_printk("ehci reset done\n");
-
-	/* Claim ownership, but do not enable yet */
-	ctrl = readl(&ehci_debug->control);
-	ctrl |= DBGP_OWNER;
-	ctrl &= ~(DBGP_ENABLED | DBGP_INUSE);
-	writel(ctrl, &ehci_debug->control);
-	udelay(1);
-
-	/* Start the ehci running */
-	cmd = readl(&ehci_regs->command);
-	cmd &= ~(CMD_LRESET | CMD_IAAD | CMD_PSE | CMD_ASE | CMD_RESET);
-	cmd |= CMD_RUN;
-	writel(cmd, &ehci_regs->command);
-
-	/* Ensure everything is routed to the EHCI */
-	writel(FLAG_CF, &ehci_regs->configured_flag);
-
-	/* Wait until the controller is no longer halted */
-	loop = 10;
-	do {
-		status = readl(&ehci_regs->status);
-		if (!(status & STS_HALT))
-			break;
-		udelay(1);
-	} while (--loop > 0);
-
-	if (!loop) {
-		dbgp_printk("ehci can not be started\n");
-		return -1;
+	/* Only reset the controller if it is not already in the
+	 * configured state */
+	if (!(readl(&ehci_regs->configured_flag) & FLAG_CF)) {
+		if (dbgp_ehci_controller_reset() != 0)
+			return -1;
+	} else {
+		dbgp_ehci_status("ehci skip - already configured");
 	}
-	dbgp_printk("ehci started\n");
 
-	/* Wait for a device to show up in the debug port */
-	ret = ehci_wait_for_port(debug_port);
-	if (ret < 0) {
-		dbgp_printk("No device found in debug port\n");
+	ret = dbgp_external_startup();
+	if (ret == -EIO)
 		goto next_debug_port;
-	}
-	dbgp_printk("ehci wait for port done\n");
-
-	/* Enable the debug port */
-	ctrl = readl(&ehci_debug->control);
-	ctrl |= DBGP_CLAIM;
-	writel(ctrl, &ehci_debug->control);
-	ctrl = readl(&ehci_debug->control);
-	if ((ctrl & DBGP_CLAIM) != DBGP_CLAIM) {
-		dbgp_printk("No device in debug port\n");
-		writel(ctrl & ~DBGP_CLAIM, &ehci_debug->control);
-		goto err;
-	}
-	dbgp_printk("debug ported enabled\n");
 
-	/* Completely transfer the debug device to the debug controller */
-	portsc = readl(&ehci_regs->port_status[debug_port - 1]);
-	portsc &= ~PORT_PE;
-	writel(portsc, &ehci_regs->port_status[debug_port - 1]);
-
-	dbgp_mdelay(100);
-
-	/* Find the debug device and make it device number 127 */
-	for (devnum = 0; devnum <= 127; devnum++) {
-		ret = dbgp_control_msg(devnum,
-			USB_DIR_IN | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
-			USB_REQ_GET_DESCRIPTOR, (USB_DT_DEBUG << 8), 0,
-			&dbgp_desc, sizeof(dbgp_desc));
-		if (ret > 0)
-			break;
-	}
-	if (devnum > 127) {
-		dbgp_printk("Could not find attached debug device\n");
-		goto err;
-	}
 	if (ret < 0) {
-		dbgp_printk("Attached device is not a debug device\n");
-		goto err;
-	}
-	dbgp_endpoint_out = dbgp_desc.bDebugOutEndpoint;
-
-	/* Move the device to 127 if it isn't already there */
-	if (devnum != USB_DEBUG_DEVNUM) {
-		ret = dbgp_control_msg(devnum,
-			USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
-			USB_REQ_SET_ADDRESS, USB_DEBUG_DEVNUM, 0, NULL, 0);
-		if (ret < 0) {
-			dbgp_printk("Could not move attached device to %d\n",
-				USB_DEBUG_DEVNUM);
-			goto err;
-		}
-		devnum = USB_DEBUG_DEVNUM;
-		dbgp_printk("debug device renamed to 127\n");
-	}
-
-	/* Enable the debug interface */
-	ret = dbgp_control_msg(USB_DEBUG_DEVNUM,
-		USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
-		USB_REQ_SET_FEATURE, USB_DEVICE_DEBUG_MODE, 0, NULL, 0);
-	if (ret < 0) {
-		dbgp_printk(" Could not enable the debug device\n");
-		goto err;
-	}
-	dbgp_printk("debug interface enabled\n");
-
-	/* Perform a small write to get the even/odd data state in sync
-	 */
-	ret = dbgp_bulk_write(USB_DEBUG_DEVNUM, dbgp_endpoint_out, " ", 1);
-	if (ret < 0) {
-		dbgp_printk("dbgp_bulk_write failed: %d\n", ret);
-		goto err;
+		/* Things didn't work so remove my claim */
+		ctrl = readl(&ehci_debug->control);
+		ctrl &= ~(DBGP_CLAIM | DBGP_OUT);
+		writel(ctrl, &ehci_debug->control);
+		return -1;
 	}
-	dbgp_printk("small write doned\n");
-
 	return 0;
-err:
-	/* Things didn't work so remove my claim */
-	ctrl = readl(&ehci_debug->control);
-	ctrl &= ~(DBGP_CLAIM | DBGP_OUT);
-	writel(ctrl, &ehci_debug->control);
-	return -1;
 
 next_debug_port:
 	port_map_tried |= (1<<(debug_port - 1));
@@ -749,6 +870,7 @@ int __init early_dbgp_init(char *s)
 
 		return -1;
 	}
+	dbgp_ehci_status("early_init_complete");
 
 	return 0;
 }
@@ -758,9 +880,27 @@ static void early_dbgp_write(struct console *con, const char *str, u32 n)
 	int chunk, ret;
 	char buf[DBGP_MAX_PACKET];
 	int use_cr = 0;
+	u32 cmd, ctrl;
+	int reset_run = 0;
 
-	if (!ehci_debug)
+	if (!ehci_debug || dbgp_not_safe)
 		return;
+
+	cmd = readl(&ehci_regs->command);
+	if (unlikely(!(cmd & CMD_RUN))) {
+		/* If the ehci controller is not in the run state do extended
+		 * checks to see if the acpi or some other initialization also
+		 * reset the ehci debug port */
+		ctrl = readl(&ehci_debug->control);
+		if (!(ctrl & DBGP_ENABLED)) {
+			dbgp_not_safe = 1;
+			dbgp_external_startup();
+		} else {
+			cmd |= CMD_RUN;
+			writel(cmd, &ehci_regs->command);
+			reset_run = 1;
+		}
+	}
 	while (n > 0) {
 		for (chunk = 0; chunk < DBGP_MAX_PACKET && n > 0;
 		     str++, chunk++, n--) {
@@ -775,8 +915,15 @@ static void early_dbgp_write(struct console *con, const char *str, u32 n)
 				use_cr = 0;
 			buf[chunk] = *str;
 		}
-		ret = dbgp_bulk_write(USB_DEBUG_DEVNUM,
-			dbgp_endpoint_out, buf, chunk);
+		if (chunk > 0) {
+			ret = dbgp_bulk_write(USB_DEBUG_DEVNUM,
+				      dbgp_endpoint_out, buf, chunk);
+		}
+	}
+	if (unlikely(reset_run)) {
+		cmd = readl(&ehci_regs->command);
+		cmd &= ~CMD_RUN;
+		writel(cmd, &ehci_regs->command);
 	}
 }
 
@@ -786,4 +933,3 @@ struct console early_dbgp_console = {
 	.flags =	CON_PRINTBUFFER,
 	.index =	-1,
 };
-

include/linux/usb/ehci_def.h

@@ -176,4 +176,9 @@ extern int __init early_dbgp_init(char *s);
 extern struct console early_dbgp_console;
 #endif /* CONFIG_EARLY_PRINTK_DBGP */
 
+#ifdef CONFIG_EARLY_PRINTK_DBGP
+/* Call backs from ehci host driver to ehci debug driver */
+extern int dbgp_external_startup(void);
+#endif
+
 #endif /* __LINUX_USB_EHCI_DEF_H */