[LinuxBIOS] USB Debug Port hardware?

[Uwe Hermann]

Hi,

just curious -- where do we get hardware to use with the USB Debug Port
debugging functionality in LinuxBIOS? Can you buy something in stores?
Is this specialized, high-price hardware? Can you build your own?
Are there any HOWTOs?

Thanks, Uwe.

[Peter Stuge]

On Sat, Oct 13, 2007 at 04:39:19PM +0200, Uwe Hermann wrote:
> just curious -- where do we get hardware to use with the USB Debug
> Port debugging functionality in LinuxBIOS? Can you buy something in
> stores?

Get the NET20DC from e.g. semiconductorstore.com.
I paid USD 80+VAT+shipping.
> Is this specialized,

Yes.
> high-price hardware?

Not that bad.
> Can you build your own?

In theory, but it's too much work IMO. It must support high speed USB
signalling and all the standalone chips that do are fine-pitch SMD
which brings it's own set of issues with PCB manufacturing and
supporting passive components even if one is comfortable soldering
the .2mm wide pins by hand.
> Are there any HOWTOs?

The USB debug class device specification contains all you need to
know about how the device functions. Note that the class spec
describes a device with USB on both ends. That's not strictly
neccessary as long as the host end of the device can keep up with the
bandwidth - important because the debug port has reduced error
recovery IIRC.

//Peter

[Uwe Hermann]

On Sat, Oct 13, 2007 at 05:24:12PM +0200, Peter Stuge wrote:
> On Sat, Oct 13, 2007 at 04:39:19PM +0200, Uwe Hermann wrote:
> > just curious -- where do we get hardware to use with the USB Debug
> > Port debugging functionality in LinuxBIOS? Can you buy something in
> > stores?
>
> Get the NET20DC from e.g. semiconductorstore.com.
> I paid USD 80+VAT+shipping.

Yeah, it's not exactly cheap, but it could be worse.
> > Are there any HOWTOs?
>
> The USB debug class device specification contains all you need to
> know about how the device functions. Note that the class spec
> describes a device with USB on both ends. That's not strictly
> neccessary as long as the host end of the device can keep up with the
> bandwidth - important because the debug port has reduced error
> recovery IIRC.

Thanks! Can you put some (short) general information and links to the
device plus a quick HOWTO for using it in Linux here?

http://linuxbios.org/EHCI_Debug_Port

Is this the only device of this type? Do you know other such products?

I guess this will become more important very soon as serial ports start
fading away from many boards...

Uwe.

[Gregg C Levine]

Hello!
Two things. One is this, wasn't our friend Bari going to be working on
something of a sort? And the other is one of, which class object does this
fall into?

On the USB portion of a current kernel I would see the usual things, then
Serial adapters and even mass storage ones, and then parallel adapters, and
finally USB Gadget ones, they would even include the odd ones that used a
USB cable such as what's packaged with some cameras to talk to the host. But
I've also seen it used with some PDA devices.

It's essentially called USB based networking.

Oh and what specific motherboards support this function.
> -----Original Message-----
> From: [e-mail]

[mailto:[e-mail]] On
> Behalf Of Peter Stuge
> Sent: Saturday, October 13, 2007 11:24 AM
> To: [e-mail]
> Subject: Re: [LinuxBIOS] USB Debug Port hardware?
>
> On Sat, Oct 13, 2007 at 04:39:19PM +0200, Uwe Hermann wrote:
> > just curious -- where do we get hardware to use with the USB Debug
> > Port debugging functionality in LinuxBIOS? Can you buy something in
> > stores?
>
> Get the NET20DC from e.g. semiconductorstore.com.
> I paid USD 80+VAT+shipping.
> > Is this specialized,
>
> Yes.
> > high-price hardware?
>
> Not that bad.
> > Can you build your own?
>
> In theory, but it's too much work IMO. It must support high speed USB
> signalling and all the standalone chips that do are fine-pitch SMD
> which brings it's own set of issues with PCB manufacturing and
> supporting passive components even if one is comfortable soldering
> the .2mm wide pins by hand.
> > Are there any HOWTOs?
>
> The USB debug class device specification contains all you need to
> know about how the device functions. Note that the class spec
> describes a device with USB on both ends. That's not strictly
> neccessary as long as the host end of the device can keep up with the
> bandwidth - important because the debug port has reduced error
> recovery IIRC.
>
> //Peter

[bari]

Gregg C Levine wrote:
> Hello!
> Two things. One is this, wasn't our friend Bari going to be working on
> something of a sort?

We talked about this back when legacy I/O (serial, parallel) was 
disappearing from chipsets. Then the Net20DC came out.

http://www.plxtech.com/products/NET2000/NET20DC/default.asp

http://www.mouser.com/search/ProductDetail.aspx?R=NET20DCvirtualkey58310000v...

And then Eric last winter wrote on 12/05/2006:

Ok due to popular demands here is the slightly fixed patch that works
on both i386 and x86_64.  For the i386 version you must not have
HIGHMEM64G enabled.

I just rolled it all into one patch as I'm to lazy to transmit all
3 of them.

Eric

arch/i386/kernel/head.S           |    8 +
  arch/x86_64/kernel/early_printk.c |  580 
+++++++++++++++++++++++++++++++++++++
  arch/x86_64/kernel/head.S         |   11 +-
  drivers/usb/host/ehci.h           |    8 +
  include/asm-i386/fixmap.h         |    1 +
  include/asm-x86_64/fixmap.h       |    1 +
  6 files changed, 608 insertions(+), 1 deletions(-)

diff --git a/arch/i386/kernel/head.S b/arch/i386/kernel/head.S
index ca31f18..f683565 100644
--- a/arch/i386/kernel/head.S
+++ b/arch/i386/kernel/head.S
@@ -135,6 +135,12 @@ page_pde_offset = (__PAGE_OFFSET >> 20);
    jb 10b
    movl %edi,(init_pg_tables_end - __PAGE_OFFSET)

+	/* Do an early initialization of the fixmap area */
+	movl $(swapper_pg_dir - __PAGE_OFFSET), %edx
+	movl $(swapper_pg_pmd - __PAGE_OFFSET), %eax
+	addl $0x007, %eax			/* 0x007 = PRESENT+RW+USER */
+	movl %eax, 4092(%edx)
+
  #ifdef CONFIG_SMP
    xorl %ebx,%ebx				/* This is the boot CPU (BSP) */
    jmp 3f
@@ -477,6 +483,8 @@ ENTRY(_stext)
  .section ".bss.page_aligned","w"
  ENTRY(swapper_pg_dir)
    .fill 1024,4,0
+ENTRY(swapper_pg_pmd)
+	.fill 1024,4,0	
  ENTRY(empty_zero_page)
    .fill 4096,1,0

diff --git a/arch/x86_64/kernel/early_printk.c 
b/arch/x86_64/kernel/early_printk.c
index d4050a5..71f2f88 100644
--- a/arch/x86_64/kernel/early_printk.c
+++ b/arch/x86_64/kernel/early_printk.c
@@ -3,9 +3,19 @@
  #include <linux/init.h>
  #include <linux/string.h>
  #include <linux/screen_info.h>
+#include <linux/usb_ch9.h>
+#include <linux/pci_regs.h>
+#include <linux/pci_ids.h>
+#include <linux/errno.h>
  #include <asm/io.h>
  #include <asm/processor.h>
  #include <asm/fcntl.h>
+#include <asm/pci-direct.h>
+#include <asm/pgtable.h>
+#include <asm/fixmap.h>
+#define EARLY_PRINTK
+#include "../../../drivers/usb/host/ehci.h"
+

/* Simple VGA output */

@@ -155,6 +165,564 @@ static struct console early_serial_console = {
    .index =	-1,
  };

+
+static struct ehci_caps __iomem *ehci_caps;
+static struct ehci_regs __iomem *ehci_regs;
+static struct ehci_dbg_port __iomem *ehci_debug;
+static unsigned dbgp_endpoint_out;
+
+#define USB_DEBUG_DEVNUM 127
+
+#define DBGP_DATA_TOGGLE	0x8800
+#define DBGP_PID_UPDATE(x, tok) \
+	((((x) ^ DBGP_DATA_TOGGLE) & 0xffff00) | ((tok) & 0xff))
+
+#define DBGP_LEN_UPDATE(x, len) (((x) & ~0x0f) | ((len) & 0x0f))
+/*
+ * USB Packet IDs (PIDs)
+ */
+
+/* token */
+#define USB_PID_OUT		0xe1
+#define USB_PID_IN		0x69
+#define USB_PID_SOF		0xa5
+#define USB_PID_SETUP		0x2d
+/* handshake */
+#define USB_PID_ACK		0xd2
+#define USB_PID_NAK		0x5a
+#define USB_PID_STALL		0x1e
+#define USB_PID_NYET		0x96
+/* data */
+#define USB_PID_DATA0		0xc3
+#define USB_PID_DATA1		0x4b
+#define USB_PID_DATA2		0x87
+#define USB_PID_MDATA		0x0f
+/* Special */
+#define USB_PID_PREAMBLE	0x3c
+#define USB_PID_ERR		0x3c
+#define USB_PID_SPLIT		0x78
+#define USB_PID_PING		0xb4
+#define USB_PID_UNDEF_0		0xf0
+
+#define USB_PID_DATA_TOGGLE	0x88
+#define DBGP_CLAIM (DBGP_OWNER | DBGP_ENABLED | DBGP_INUSE)
+
+#define PCI_CAP_ID_EHCI_DEBUG	0xa
+
+#define HUB_ROOT_RESET_TIME	50	/* times are in msec */
+#define HUB_SHORT_RESET_TIME	10
+#define HUB_LONG_RESET_TIME	200
+#define HUB_RESET_TIMEOUT	500
+
+#define DBGP_MAX_PACKET		8
+
+static int dbgp_wait_until_complete(void)
+{
+	unsigned ctrl;
+	for (;;) {
+		ctrl = readl(&ehci_debug->control);
+		/* Stop when the transaction is finished */
+		if (ctrl & DBGP_DONE)
+			break;
+	}
+	/* Now that we have observed the completed transaction,
+	 * clear the done bit.
+	 */
+	writel(ctrl | DBGP_DONE, &ehci_debug->control);
+	return (ctrl & DBGP_ERROR) ? -DBGP_ERRCODE(ctrl) : DBGP_LEN(ctrl);
+}
+
+static void dbgp_mdelay(int ms)
+{
+	int i;
+	while (ms--) {
+		for (i = 0; i < 1000; i++)
+			outb(0x1, 0x80);
+	}
+}
+
+static void dbgp_breath(void)
+{
+	/* Sleep to give the debug port a chance to breathe */
+}
+
+static int dbgp_wait_until_done(unsigned ctrl)
+{
+	unsigned pids, lpid;
+	int ret;
+
+retry:
+	writel(ctrl | DBGP_GO, &ehci_debug->control);
+	ret = dbgp_wait_until_complete();
+	pids = readl(&ehci_debug->pids);
+	lpid = DBGP_PID_GET(pids);
+
+	if (ret < 0)
+		return ret;
+
+	/* If the port is getting full or it has dropped data
+	 * start pacing ourselves, not necessary but it's friendly.
+	 */
+	if ((lpid == USB_PID_NAK) || (lpid == USB_PID_NYET))
+		dbgp_breath();
+	
+	/* If I get a NACK reissue the transmission */
+	if (lpid == USB_PID_NAK)
+		goto retry;
+
+	return ret;
+}
+
+static void dbgp_set_data(const void *buf, int size)
+{
+	const unsigned char *bytes = buf;
+	unsigned lo, hi;
+	int i;
+	lo = hi = 0;
+	for (i = 0; i < 4 && i < size; i++)
+		lo |= bytes[i] << (8*i);
+	for (; i < 8 && i < size; i++)
+		hi |= bytes[i] << (8*(i - 4));
+	writel(lo, &ehci_debug->data03);
+	writel(hi, &ehci_debug->data47);
+}
+
+static void dbgp_get_data(void *buf, int size)
+{
+	unsigned char *bytes = buf;
+	unsigned lo, hi;
+	int i;
+	lo = readl(&ehci_debug->data03);
+	hi = readl(&ehci_debug->data47);
+	for (i = 0; i < 4 && i < size; i++)
+		bytes[i] = (lo >> (8*i)) & 0xff;
+	for (; i < 8 && i < size; i++)
+		bytes[i] = (hi >> (8*(i - 4))) & 0xff;
+}
+
+static int dbgp_bulk_write(unsigned devnum, unsigned endpoint, const 
char *bytes, int size)
+{
+	unsigned pids, addr, ctrl;
+	int ret;
+	if (size > DBGP_MAX_PACKET)
+		return -1;
+
+	addr = DBGP_EPADDR(devnum, endpoint);
+
+	pids = readl(&ehci_debug->pids);
+	pids = DBGP_PID_UPDATE(pids, USB_PID_OUT);
+	
+	ctrl = readl(&ehci_debug->control);
+	ctrl = DBGP_LEN_UPDATE(ctrl, size);
+	ctrl |= DBGP_OUT;
+	ctrl |= DBGP_GO;
+
+	dbgp_set_data(bytes, size);
+	writel(addr, &ehci_debug->address);
+	writel(pids, &ehci_debug->pids);
+
+	ret = dbgp_wait_until_done(ctrl);
+	if (ret < 0) {
+		return ret;
+	}
+	return ret;
+}
+
+static int dbgp_bulk_read(unsigned devnum, unsigned endpoint, void 
*data, int size)
+{
+	unsigned pids, addr, ctrl;
+	int ret;
+
+	if (size > DBGP_MAX_PACKET)
+		return -1;
+
+	addr = DBGP_EPADDR(devnum, endpoint);
+
+	pids = readl(&ehci_debug->pids);
+	pids = DBGP_PID_UPDATE(pids, USB_PID_IN);
+		
+	ctrl = readl(&ehci_debug->control);
+	ctrl = DBGP_LEN_UPDATE(ctrl, size);
+	ctrl &= ~DBGP_OUT;
+	ctrl |= DBGP_GO;
+		
+	writel(addr, &ehci_debug->address);
+	writel(pids, &ehci_debug->pids);
+	ret = dbgp_wait_until_done(ctrl);
+	if (ret < 0)
+		return ret;
+	if (size > ret)
+		size = ret;
+	dbgp_get_data(data, size);
+	return ret;
+}
+
+static int dbgp_control_msg(unsigned devnum, int requesttype, int request,
+	int value, int index, void *data, int size)
+{
+	unsigned pids, addr, ctrl;
+	struct usb_ctrlrequest req;
+	int read;
+	int ret;
+
+	read = (requesttype & USB_DIR_IN) != 0;
+	if (size > (read?DBGP_MAX_PACKET:0))
+		return -1;
+	
+	/* Compute the control message */
+	req.bRequestType = requesttype;
+	req.bRequest = request;
+	req.wValue = value;
+	req.wIndex = index;
+	req.wLength = size;
+
+	pids = DBGP_PID_SET(USB_PID_DATA0, USB_PID_SETUP);
+	addr = DBGP_EPADDR(devnum, 0);
+
+	ctrl = readl(&ehci_debug->control);
+	ctrl = DBGP_LEN_UPDATE(ctrl, sizeof(req));
+	ctrl |= DBGP_OUT;
+	ctrl |= DBGP_GO;
+
+	/* Send the setup message */
+	dbgp_set_data(&req, sizeof(req));
+	writel(addr, &ehci_debug->address);
+	writel(pids, &ehci_debug->pids);
+	ret = dbgp_wait_until_done(ctrl);
+	if (ret < 0)
+		return ret;
+
+
+	/* Read the result */
+	ret = dbgp_bulk_read(devnum, 0, data, size);
+	return ret;
+}
+
+
+/* Find a PCI capability */
+static __u32 __init find_cap(int num, int slot, int func, int cap)
+{
+	u8 pos;
+	int bytes;
+	if (!(read_pci_config_16(num,slot,func,PCI_STATUS) & PCI_STATUS_CAP_LIST))
+		return 0;
+	pos = read_pci_config_byte(num,slot,func,PCI_CAPABILITY_LIST);
+	for (bytes = 0; bytes < 48 && pos >= 0x40; bytes++) {
+		u8 id;
+		pos &= ~3;
+		id = read_pci_config_byte(num,slot,func,pos+PCI_CAP_LIST_ID);
+		if (id == 0xff)
+			break;
+		if (id == cap)
+			return pos;
+		pos = read_pci_config_byte(num,slot,func,pos+PCI_CAP_LIST_NEXT);
+	}
+	return 0;
+}
+
+static __u32 __init find_dbgp(int ehci_num, unsigned *rbus, unsigned 
*rslot, unsigned *rfunc)
+{
+	unsigned bus, slot, func;
+	
+	for (bus = 0; bus < 256; bus++) {
+		for (slot = 0; slot < 32; slot++) {
+			for (func = 0; func < 8; func++) {
+				u32 class;
+				unsigned cap;
+				class = read_pci_config(bus, slot, func, PCI_CLASS_REVISION);
+				if ((class >> 8) != PCI_CLASS_SERIAL_USB_EHCI)
+					continue;
+				cap = find_cap(bus, slot, func, PCI_CAP_ID_EHCI_DEBUG);
+				if (!cap)
+					continue;
+				if (ehci_num-- != 0)
+					continue;
+				*rbus = bus;
+				*rslot = slot;
+				*rfunc = func;
+				return cap;
+			}
+		}
+	}
+	return 0;
+}
+
+static int ehci_reset_port(int port)
+{
+	unsigned portsc;
+	unsigned delay_time, delay;
+
+	/* Reset the usb debug port */
+	portsc = readl(&ehci_regs->port_status[port - 1]);
+	portsc &= ~PORT_PE;
+	portsc |= PORT_RESET;
+	writel(portsc, &ehci_regs->port_status[port - 1]);
+
+	delay = HUB_ROOT_RESET_TIME;
+	for (delay_time = 0; delay_time < HUB_RESET_TIMEOUT;
+	     delay_time += delay) {
+		dbgp_mdelay(delay);
+
+		portsc = readl(&ehci_regs->port_status[port - 1]);
+		if (portsc & PORT_RESET) {
+			/* force reset to complete */
+			writel(portsc & ~(PORT_RWC_BITS | PORT_RESET),
+				&ehci_regs->port_status[port - 1]);
+			while (portsc & PORT_RESET)
+				portsc = readl(&ehci_regs->port_status[port - 1]);
+		}
+
+		/* Device went away? */
+		if (!(portsc & PORT_CONNECT))
+			return -ENOTCONN;
+
+		/* bomb out completely if something weird happend */
+		if ((portsc & PORT_CSC))
+			return -EINVAL;
+
+		/* If we've finished resetting, then break out of the loop */
+		if (!(portsc & PORT_RESET) && (portsc & PORT_PE))
+			return 0;
+	}
+	return -EBUSY;
+}
+
+static int ehci_wait_for_port(int port)
+{
+	unsigned status;
+	int ret, reps;
+	for (reps = 0; reps >= 0; reps++) {
+		status = readl(&ehci_regs->status);
+		if (status & STS_PCD) {
+			ret = ehci_reset_port(port);
+			if (ret == 0)
+				return 0;
+		}
+	}
+	return -ENOTCONN;
+}
+
+
+#define DBGP_DEBUG 0
+#if DBGP_DEBUG
+void early_printk(const char *fmt, ...);
+# define dbgp_printk early_printk
+#else
+static inline void dbgp_printk(const char *fmt, ...) { }
+#endif
+
+static int ehci_setup(void)
+{
+	unsigned cmd, ctrl, status, portsc, hcs_params, debug_port, n_ports;
+	int ret;
+
+	hcs_params = readl(&ehci_caps->hcs_params);
+	debug_port = HCS_DEBUG_PORT(hcs_params);
+	n_ports    = HCS_N_PORTS(hcs_params);
+
+	dbgp_printk("debug_port: %d\n", debug_port);
+	dbgp_printk("n_ports:    %d\n", n_ports);
+
+	/* Reset the EHCI controller */
+	cmd = readl(&ehci_regs->command);
+	cmd |=CMD_RESET;
+	writel(cmd, &ehci_regs->command);
+	while (cmd & CMD_RESET)
+		cmd = readl(&ehci_regs->command);
+
+	/* 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);
+
+	/* 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 */
+	do {
+		status = readl(&ehci_regs->status);
+	} while (status & STS_HALT);
+
+	/* 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");
+		return -1;
+	}
+
+	/* 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 -1;
+
+	}
+
+	/* 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]);
+
+	return 0;
+}
+
+static __init void early_dbgp_init(char *s)
+{
+	struct usb_debug_descriptor dbgp_desc;
+	void __iomem *ehci_bar;
+	unsigned ctrl, devnum;
+	unsigned bus, slot, func, cap;
+	unsigned debug_port, bar, offset;
+	unsigned bar_val;
+	unsigned dbgp_num;
+	char *e;
+	int ret;
+
+	if (!early_pci_allowed())
+		return;
+
+	dbgp_num = 0;
+	if (*s) {
+		dbgp_num = simple_strtoul(s, &e, 10);
+	}
+	dbgp_printk("dbgp_num: %d\n", dbgp_num);
+	cap = find_dbgp(dbgp_num, &bus, &slot, &func);
+	if (!cap)
+		return;
+
+	dbgp_printk("Found EHCI debug port\n");
+
+	debug_port = read_pci_config(bus, slot, func, cap);
+	bar = (debug_port >> 29) & 0x7;
+	bar = (bar * 4) + 0xc;
+	offset = (debug_port >> 16) & 0xfff;
+	dbgp_printk("bar: %02x offset: %03x\n", bar, offset);
+	if (bar != PCI_BASE_ADDRESS_0) {
+		dbgp_printk("only debug ports on bar 1 handled.\n");
+		return;
+	}
+
+	bar_val = read_pci_config(bus, slot, func, PCI_BASE_ADDRESS_0);
+	dbgp_printk("bar: %02x offset: %03x\n", bar, offset);
+	if (bar_val & ~PCI_BASE_ADDRESS_MEM_MASK) {
+		dbgp_printk("only simple 32bit mmio bars supported\n");
+		return;
+	}
+		
+
+	/* FIXME I don't have the bar size so just guess PAGE_SIZE is more
+	 * than enough.  1K is the biggest I have seen.
+	 */
+	dbgp_printk("dbgp pre-set_fixmap_nocache\n");
+	set_fixmap_nocache(FIX_DBGP_BASE, bar_val & PAGE_MASK);
+	dbgp_printk("dbgp post-set_fixmap_nocache\n");
+	ehci_bar = (void __iomem *)__fix_to_virt(FIX_DBGP_BASE);
+	ehci_bar += bar_val & ~PAGE_MASK;
+	dbgp_printk("ehci_bar: %p\n", ehci_bar);
+
+	ehci_caps  = ehci_bar;
+	ehci_regs  = ehci_bar + HC_LENGTH(readl(&ehci_caps->hc_capbase));
+	ehci_debug = ehci_bar + offset;
+
+	ret = ehci_setup();
+	if (ret < 0) {
+		dbgp_printk("ehci_setup failed\n");
+		return;
+	}
+
+	/* 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;
+	}
+
+	/* 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;
+	}
+
+	/* 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;
+	}
+
+
+	return;
+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;
+}
+
+static void early_dbgp_write(struct console *con, const char *str, 
unsigned n)
+{
+	int chunk, ret;
+	if (!ehci_debug)
+		return;
+	while (n > 0) {
+		chunk = n;
+		if (chunk > DBGP_MAX_PACKET)
+			chunk = DBGP_MAX_PACKET;
+		ret = dbgp_bulk_write(USB_DEBUG_DEVNUM,
+			dbgp_endpoint_out, str, chunk);
+		str += chunk;
+		n -= chunk;
+	}
+}
+
+static struct console early_dbgp_console = {
+	.name =		"earlydbg",
+	.write =	early_dbgp_write,
+	.flags = 	CON_PRINTBUFFER,
+	.index = 	-1,
+};
+
  /* Console interface to a host file on AMD's SimNow! */

static int simnow_fd;
@@ -242,8 +810,20 @@ static int __init setup_early_printk(char *buf)
    	simnow_init(buf + 6);
    	early_console = &simnow_console;
    	keep_early = 1;
+	} else if (!strncmp(buf, "dbgp", 4)) {
+		early_dbgp_init(buf + 4);
+		early_console = &early_dbgp_console;
    }
    register_console(early_console);
+#if DBGP_DEBUG
+	{
+		static const char dbgp_test_str[] =
+			"The quick brown fox jumped over the lazy dog!\n";
+		early_dbgp_init("");
+		early_dbgp_write(&early_dbgp_console,
+			dbgp_test_str, sizeof(dbgp_test_str) - 1);
+	}
+#endif
    return 0;
  }

diff --git a/arch/x86_64/kernel/head.S b/arch/x86_64/kernel/head.S
index 2f65469..4004965 100644
--- a/arch/x86_64/kernel/head.S
+++ b/arch/x86_64/kernel/head.S
@@ -271,7 +271,16 @@ NEXT_PAGE(level3_kernel_pgt)
    .fill	510,8,0
    /* (248-(2*1024*1024*1024)-((239)*511))/(230) = 510 */
    .quad	phys_level2_kernel_pgt | 0x007
-	.fill	1,8,0
+	.quad	phys_level2_fixmap_pgt | 0x007
+
+NEXT_PAGE(level2_fixmap_pgt)
+	.fill	506,8,0
+	.quad	phys_level1_fixmap_pgt | 0x007
+	/* 8MB reserved for vsyscalls + a 2MB hole = 4 + 1 entries */
+	.fill	5,8,0
+
+NEXT_PAGE(level1_fixmap_pgt)
+	.fill	512,8,0

NEXT_PAGE(level2_ident_pgt)
    /* 40MB for bootup. 	*/
diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h
index bbc3082..0a67192 100644
--- a/drivers/usb/host/ehci.h
+++ b/drivers/usb/host/ehci.h
@@ -46,6 +46,7 @@ struct ehci_stats {

#define	EHCI_MAX_ROOT_PORTS	15		/* see HCS_N_PORTS */

+#ifndef EARLY_PRINTK
  struct ehci_hcd {			/* one per controller */
    /* glue to PCI and HCD framework */
    struct ehci_caps __iomem *caps;
@@ -160,6 +161,7 @@ timer_action (struct ehci_hcd *ehci, enum 
ehci_timer_action action)
    	mod_timer (&ehci->watchdog, t);
    }
  }
+#endif /* EARLY_PRINTK */

/*-------------------------------------------------------------------------*/

@@ -384,6 +386,7 @@ union ehci_shadow {
   * These appear in both the async and (for interrupt) periodic schedules.
   */

+#ifndef EARLY_PRINTK
  struct ehci_qh {
    /* first part defined by EHCI spec */
    __le32			hw_next;	 /* see EHCI 3.6.1 */
@@ -432,6 +435,7 @@ struct ehci_qh {
  #define NO_FRAME ((unsigned short)~0)			/* pick new start */
    struct usb_device	*dev;		/* access to TT */
  } __attribute__ ((aligned (32)));
+#endif /* EARLY_PRITNK */

/*-------------------------------------------------------------------------*/

@@ -601,6 +605,8 @@ struct ehci_fstn {
    union ehci_shadow	fstn_next;	/* ptr to periodic q entry */
  } __attribute__ ((aligned (32)));

+#ifndef EARLY_PRINTK
+

/*-------------------------------------------------------------------------*/

#ifdef CONFIG_USB_EHCI_ROOT_HUB_TT
@@ -659,4 +665,6 @@ ehci_port_speed(struct ehci_hcd *ehci, unsigned int 
portsc)

/*-------------------------------------------------------------------------*/

+#endif /* EARLY_PRINTK */
+
  #endif /* __LINUX_EHCI_HCD_H */
diff --git a/include/asm-i386/fixmap.h b/include/asm-i386/fixmap.h
index 02428cb..ea08885 100644
--- a/include/asm-i386/fixmap.h
+++ b/include/asm-i386/fixmap.h
@@ -56,6 +56,7 @@ extern unsigned long __FIXADDR_TOP;
  enum fixed_addresses {
    FIX_HOLE,
    FIX_VDSO,
+	FIX_DBGP_BASE,
  #ifdef CONFIG_X86_LOCAL_APIC
    FIX_APIC_BASE,	/* local (CPU) APIC) -- required for SMP or not */
  #endif
diff --git a/include/asm-x86_64/fixmap.h b/include/asm-x86_64/fixmap.h
index 1b620db..1f2978a 100644
--- a/include/asm-x86_64/fixmap.h
+++ b/include/asm-x86_64/fixmap.h
@@ -36,6 +36,7 @@ enum fixed_addresses {
    VSYSCALL_LAST_PAGE,
    VSYSCALL_FIRST_PAGE = VSYSCALL_LAST_PAGE + 
((VSYSCALL_END-VSYSCALL_START) >> PAGE_SHIFT) - 1,
    VSYSCALL_HPET,
+	FIX_DBGP_BASE,
    FIX_HPET_BASE,
    FIX_APIC_BASE,	/* local (CPU) APIC) -- required for SMP or not */
    FIX_IO_APIC_BASE_0,

-- linuxbios mailing list [e-mail] 
http://www.openbios.org/mailman/listinfo/linuxbios
> > Get the NET20DC from e.g. semiconductorstore.com.
> > I paid USD 80+VAT+shipping.
> > > Is this specialized,
> >
> > Yes.
> > > high-price hardware?
> >
> > Not that bad.
> > > Can you build your own?
> >
> > In theory, but it's too much work IMO. It must support high speed USB
> > signalling and all the standalone chips that do are fine-pitch SMD
> > which brings it's own set of issues with PCB manufacturing and
> > supporting passive components even if one is comfortable soldering
> > the .2mm wide pins by hand.
> > > Are there any HOWTOs?
> >
> > The USB debug class device specification contains all you need to
> > know about how the device functions. Note that the class spec
> > describes a device with USB on both ends. That's not strictly
> > neccessary as long as the host end of the device can keep up with the
> > bandwidth - important because the debug port has reduced error
> > recovery IIRC.
> >
> > //Peter