x86: usb debug port early console, v4

based on work from Eric, and add some timeout so don't dead loop when debug
device is not installed

v2: fix checkpatch warning
v3: move ehci struct def to linux/usrb/ehci_def.h from host/ehci.h
    also add CONFIG_EARLY_PRINTK_DBGP to disable it by default
v4: address comments from Ingo, seperate ehci reg def moving to another patch
    also add auto detect port that connect to debug device for Nvidia
    southbridge

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: "Arjan van de Ven" <arjan@infradead.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Greg KH" <greg@kroah.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 759 insertions, 3 deletions

diff --git a/arch/x86/kernel/early_printk.c b/arch/x86/kernel/early_printk.c
index ff9e7350da54..28155acf706e 100644
--- a/arch/x86/kernel/early_printk.c
+++ b/arch/x86/kernel/early_printk.c
@@ -3,11 +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/setup.h>
 #include <xen/hvc-console.h>
+#include <asm/pci-direct.h>
+#include <asm/pgtable.h>
+#include <asm/fixmap.h>
+#include <linux/usb/ehci_def.h>
 
 /* Simple VGA output */
 #define VGABASE         (__ISA_IO_base + 0xb8000)
@@ -78,6 +86,7 @@ static int early_serial_base = 0x3f8;  /* ttyS0 */
 static int early_serial_putc(unsigned char ch)
 {
         unsigned timeout = 0xffff;
+
         while ((inb(early_serial_base + LSR) & XMTRDY) == 0 && --timeout)
                 cpu_relax();
         outb(ch, early_serial_base + TXR);
@@ -151,6 +160,721 @@ static struct console early_serial_console = {
         .index =        -1,
 };
 
+#ifdef CONFIG_EARLY_PRINTK_DBGP
+
+static struct ehci_caps __iomem *ehci_caps;
+static struct ehci_regs __iomem *ehci_regs;
+static struct ehci_dbg_port __iomem *ehci_debug;
+static unsigned int dbgp_endpoint_out;
+
+struct ehci_dev {
+        u32 bus;
+        u32 slot;
+        u32 func;
+};
+
+static struct ehci_dev ehci_dev;
+
+#define USB_DEBUG_DEVNUM 127
+
+#define DBGP_DATA_TOGGLE        0x8800
+
+static inline u32 dbgp_pid_update(u32 x, u32 tok)
+{
+        return ((x ^ DBGP_DATA_TOGGLE) & 0xffff00) | (tok & 0xff);
+}
+
+static inline u32 dbgp_len_update(u32 x, u32 len)
+{
+        return (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)
+{
+        u32 ctrl;
+        int loop = 0x100000;
+
+        do {
+                ctrl = readl(&ehci_debug->control);
+                /* Stop when the transaction is finished */
+                if (ctrl & DBGP_DONE)
+                        break;
+        } while (--loop > 0);
+
+        if (!loop)
+                return -1;
+
+        /*
+         * 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)
+{
+        u32 pids, lpid;
+        int ret;
+        int loop = 3;
+
+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) {
+                if (--loop > 0)
+                        goto retry;
+        }
+
+        return ret;
+}
+
+static void dbgp_set_data(const void *buf, int size)
+{
+        const unsigned char *bytes = buf;
+        u32 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;
+        u32 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)
+{
+        u32 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)
+{
+        u32 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)
+{
+        u32 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 */
+        return dbgp_bulk_read(devnum, 0, data, size);
+}
+
+
+/* Find a PCI capability */
+static u32 __init find_cap(u32 num, u32 slot, u32 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(u32 bus, u32 slot, u32 func)
+{
+        u32 class;
+
+        class = read_pci_config(bus, slot, func, PCI_CLASS_REVISION);
+        if ((class >> 8) != PCI_CLASS_SERIAL_USB_EHCI)
+                return 0;
+
+        return find_cap(bus, slot, func, PCI_CAP_ID_EHCI_DEBUG);
+}
+
+static u32 __init find_dbgp(int ehci_num, u32 *rbus, u32 *rslot, u32 *rfunc)
+{
+        u32 bus, slot, func;
+
+        for (bus = 0; bus < 256; bus++) {
+                for (slot = 0; slot < 32; slot++) {
+                        for (func = 0; func < 8; func++) {
+                                unsigned cap;
+
+                                cap = __find_dbgp(bus, slot, func);
+
+                                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)
+{
+        u32 portsc;
+        u32 delay_time, delay;
+        int loop;
+
+        /* 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 */
+                        loop = 2;
+                        writel(portsc & ~(PORT_RWC_BITS | PORT_RESET),
+                                &ehci_regs->port_status[port - 1]);
+                        do {
+                                portsc = readl(&ehci_regs->port_status[port-1]);
+                        } while ((portsc & PORT_RESET) && (--loop > 0));
+                }
+
+                /* 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)
+{
+        u32 status;
+        int ret, reps;
+
+        for (reps = 0; reps < 3; reps++) {
+                dbgp_mdelay(100);
+                status = readl(&ehci_regs->status);
+                if (status & STS_PCD) {
+                        ret = ehci_reset_port(port);
+                        if (ret == 0)
+                                return 0;
+                }
+        }
+        return -ENOTCONN;
+}
+
+#ifdef DBGP_DEBUG
+# define dbgp_printk early_printk
+#else
+static inline void dbgp_printk(const char *fmt, ...) { }
+#endif
+
+typedef void (*set_debug_port_t)(int port);
+
+static void default_set_debug_port(int port)
+{
+}
+
+static set_debug_port_t set_debug_port = default_set_debug_port;
+
+static void nvidia_set_debug_port(int port)
+{
+        u32 dword;
+        dword = read_pci_config(ehci_dev.bus, ehci_dev.slot, ehci_dev.func,
+                                 0x74);
+        dword &= ~(0x0f<<12);
+        dword |= ((port & 0x0f)<<12);
+        write_pci_config(ehci_dev.bus, ehci_dev.slot, ehci_dev.func, 0x74,
+                                 dword);
+        dbgp_printk("set debug port to %d\n", port);
+}
+
+static void __init detect_set_debug_port(void)
+{
+        u32 vendorid;
+
+        vendorid = read_pci_config(ehci_dev.bus, ehci_dev.slot, ehci_dev.func,
+                 0x00);
+
+        if ((vendorid & 0xffff) == 0x10de) {
+                dbgp_printk("using nvidia set_debug_port\n");
+                set_debug_port = nvidia_set_debug_port;
+        }
+}
+
+static int __init ehci_setup(void)
+{
+        struct usb_debug_descriptor dbgp_desc;
+        u32 cmd, ctrl, status, 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;
+
+try_next_time:
+        port_map_tried = 0;
+
+try_next_port:
+
+        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);
+
+        for (i = 1; i <= n_ports; i++) {
+                portsc = readl(&ehci_regs->port_status[i-1]);
+                dbgp_printk("portstatus%d: %08x\n", i, portsc);
+        }
+
+        if (port_map_tried && (new_debug_port != debug_port)) {
+                if (--playtimes) {
+                        set_debug_port(new_debug_port);
+                        goto try_next_time;
+                }
+                return -1;
+        }
+
+        loop = 10;
+        /* 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);
+
+        /* 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);
+        } while ((status & STS_HALT) && (--loop > 0));
+
+        if (!loop) {
+                dbgp_printk("ehci can be started\n");
+                return -1;
+        }
+        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");
+                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;
+        }
+        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));
+        new_debug_port = ((debug_port-1+1)%n_ports) + 1;
+        if (port_map_tried != ((1<<n_ports) - 1)) {
+                set_debug_port(new_debug_port);
+                goto try_next_port;
+        }
+        if (--playtimes) {
+                set_debug_port(new_debug_port);
+                goto try_next_time;
+        }
+
+        return -1;
+}
+
+static int __init early_dbgp_init(char *s)
+{
+        u32 debug_port, bar, offset;
+        u32 bus, slot, func, cap;
+        void __iomem *ehci_bar;
+        u32 dbgp_num;
+        u32 bar_val;
+        char *e;
+        int ret;
+        u8 byte;
+
+        if (!early_pci_allowed())
+                return -1;
+
+        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 -1;
+
+        dbgp_printk("Found EHCI debug port on %02x:%02x.%1x\n", bus, slot,
+                         func);
+
+        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 -1;
+        }
+
+        bar_val = read_pci_config(bus, slot, func, PCI_BASE_ADDRESS_0);
+        dbgp_printk("bar_val: %02x offset: %03x\n", bar_val, offset);
+        if (bar_val & ~PCI_BASE_ADDRESS_MEM_MASK) {
+                dbgp_printk("only simple 32bit mmio bars supported\n");
+
+                return -1;
+        }
+
+        /* double check if the mem space is enabled */
+        byte = read_pci_config_byte(bus, slot, func, 0x04);
+        if (!(byte & 0x2)) {
+                byte  |= 0x02;
+                write_pci_config_byte(bus, slot, func, 0x04, byte);
+                dbgp_printk("mmio for ehci enabled\n");
+        }
+
+        /*
+         * FIXME I don't have the bar size so just guess PAGE_SIZE is more
+         * than enough.  1K is the biggest I have seen.
+         */
+        set_fixmap_nocache(FIX_DBGP_BASE, bar_val & PAGE_MASK);
+        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;
+        ehci_dev.bus = bus;
+        ehci_dev.slot = slot;
+        ehci_dev.func = func;
+
+        detect_set_debug_port();
+
+        ret = ehci_setup();
+        if (ret < 0) {
+                dbgp_printk("ehci_setup failed\n");
+                ehci_debug = 0;
+
+                return -1;
+        }
+
+        return 0;
+}
+
+static void early_dbgp_write(struct console *con, const char *str, u32 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,
+};
+#endif
+
 /* Console interface to a host file on AMD's SimNow! */
 
 static int simnow_fd;
@@ -165,6 +889,7 @@ enum {
 static noinline long simnow(long cmd, long a, long b, long c)
 {
         long ret;
+
         asm volatile("cpuid" :
                      "=a" (ret) :
                      "b" (a), "c" (b), "d" (c), "0" (MAGIC1), "D" (cmd + MAGIC2));
@@ -174,6 +899,7 @@ static noinline long simnow(long cmd, long a, long b, long c)
 static void __init simnow_init(char *str)
 {
         char *fn = "klog";
+
         if (*str == '=')
                 fn = ++str;
         /* error ignored */
@@ -208,10 +934,11 @@ asmlinkage void early_printk(const char *fmt, ...)
         va_end(ap);
 }
 
-static int __initdata keep_early;
 
 static int __init setup_early_printk(char *buf)
 {
+        int keep_early;
+
         if (!buf)
                 return 0;
 
@@ -219,8 +946,7 @@ static int __init setup_early_printk(char *buf)
                 return 0;
         early_console_initialized = 1;
 
-        if (strstr(buf, "keep"))
-                keep_early = 1;
+        keep_early = (strstr(buf, "keep") != NULL);
 
         if (!strncmp(buf, "serial", 6)) {
                 early_serial_init(buf + 6);
@@ -238,6 +964,17 @@ static int __init setup_early_printk(char *buf)
                 simnow_init(buf + 6);
                 early_console = &simnow_console;
                 keep_early = 1;
+#ifdef CONFIG_EARLY_PRINTK_DBGP
+        } else if (!strncmp(buf, "dbgp", 4)) {
+                if (early_dbgp_init(buf+4) < 0)
+                        return 0;
+                early_console = &early_dbgp_console;
+                /*
+                 * usb subsys will reset ehci controller, so don't keep
+                 * that early console
+                 */
+                keep_early = 0;
+#endif
 #ifdef CONFIG_HVC_XEN
         } else if (!strncmp(buf, "xen", 3)) {
                 early_console = &xenboot_console;
@@ -251,4 +988,23 @@ static int __init setup_early_printk(char *buf)
         register_console(early_console);
         return 0;
 }
+
+void __init enable_debug_console(char *buf)
+{
+#ifdef DBGP_DEBUG
+        struct console *old_early_console = NULL;
+
+        if (early_console_initialized && early_console) {
+                old_early_console = early_console;
+                unregister_console(early_console);
+                early_console_initialized = 0;
+        }
+
+        setup_early_printk(buf);
+
+        if (early_console == old_early_console && old_early_console)
+                register_console(old_early_console);
+#endif
+}
+
 early_param("earlyprintk", setup_early_printk);