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/*
 * Copyright (c) 2000-2002 by David Brownell
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linuxcomp.h>

#include <linux/config.h>

#ifdef CONFIG_USB_DEBUG
        #define DEBUG
#else
        #undef DEBUG
#endif

#include <linux/module.h>
#include <linux/pci.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/ioport.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/smp_lock.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/timer.h>
#include <linux/list.h>
#include <linux/interrupt.h>
#include <linux/reboot.h>
#include <linux/usb.h>
#include <linux/moduleparam.h>

#include "../core/hcd.h"

#include <asm/byteorder.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/system.h>
#include <asm/unaligned.h>


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

/*
 * EHCI hc_driver implementation ... experimental, incomplete.
 * Based on the final 1.0 register interface specification.
 *
 * USB 2.0 shows up in upcoming www.pcmcia.org technology.
 * First was PCMCIA, like ISA; then CardBus, which is PCI.
 * Next comes "CardBay", using USB 2.0 signals.
 *
 * Contains additional contributions by Brad Hards, Rory Bolt, and others.
 * Special thanks to Intel and VIA for providing host controllers to
 * test this driver on, and Cypress (including In-System Design) for
 * providing early devices for those host controllers to talk to!
 *
 * HISTORY:
 *
 * 2002-11-29   Correct handling for hw async_next register.
 * 2002-08-06   Handling for bulk and interrupt transfers is mostly shared;
 *      only scheduling is different, no arbitrary limitations.
 * 2002-07-25   Sanity check PCI reads, mostly for better cardbus support,
 *      clean up HC run state handshaking.
 * 2002-05-24   Preliminary FS/LS interrupts, using scheduling shortcuts
 * 2002-05-11   Clear TT errors for FS/LS ctrl/bulk.  Fill in some other
 *      missing pieces:  enabling 64bit dma, handoff from BIOS/SMM.
 * 2002-05-07   Some error path cleanups to report better errors; wmb();
 *      use non-CVS version id; better iso bandwidth claim.
 * 2002-04-19   Control/bulk/interrupt submit no longer uses giveback() on
 *      errors in submit path.  Bugfixes to interrupt scheduling/processing.
 * 2002-03-05   Initial high-speed ISO support; reduce ITD memory; shift
 *      more checking to generic hcd framework (db).  Make it work with
 *      Philips EHCI; reduce PCI traffic; shorten IRQ path (Rory Bolt).
 * 2002-01-14   Minor cleanup; version synch.
 * 2002-01-08   Fix roothub handoff of FS/LS to companion controllers.
 * 2002-01-04   Control/Bulk queuing behaves.
 *
 * 2001-12-12   Initial patch version for Linux 2.5.1 kernel.
 * 2001-June    Works with usb-storage and NEC EHCI on 2.4
 */

#define DRIVER_VERSION "2003-Jun-13"
#define DRIVER_AUTHOR "David Brownell"
#define DRIVER_DESC "USB 2.0 'Enhanced' Host Controller (EHCI) Driver"

static const char       hcd_name [] = "ehci_hcd";


// #define EHCI_VERBOSE_DEBUG
// #define have_split_iso

#ifdef DEBUG
#define EHCI_STATS
#endif

/* magic numbers that can affect system performance */
#define EHCI_TUNE_CERR          3       /* 0-3 qtd retries; 0 == don't stop */
#define EHCI_TUNE_RL_HS         4       /* nak throttle; see 4.9 */
#define EHCI_TUNE_RL_TT         0
#define EHCI_TUNE_MULT_HS       1       /* 1-3 transactions/uframe; 4.10.3 */
#define EHCI_TUNE_MULT_TT       1
#define EHCI_TUNE_FLS           2       /* (small) 256 frame schedule */

#define EHCI_IAA_JIFFIES        (HZ/100)        /* arbitrary; ~10 msec */
#define EHCI_IO_JIFFIES         (HZ/10)         /* io watchdog > irq_thresh */
#define EHCI_ASYNC_JIFFIES      (HZ/20)         /* async idle timeout */
#define EHCI_SHRINK_JIFFIES     (HZ/200)        /* async qh unlink delay */

/* Initial IRQ latency:  lower than default */
static int log2_irq_thresh = 0;         // 0 to 6

/*module_param (log2_irq_thresh, int, S_IRUGO);
MODULE_PARM_DESC (log2_irq_thresh, "log2 IRQ latency, 1-64 microframes");
*/

#define INTR_MASK (STS_IAA | STS_FATAL | STS_ERR | STS_INT)

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

#include "ehci.h"
#include "ehci-dbg.c"

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

/*
 * handshake - spin reading hc until handshake completes or fails
 * @ptr: address of hc register to be read
 * @mask: bits to look at in result of read
 * @done: value of those bits when handshake succeeds
 * @usec: timeout in microseconds
 *
 * Returns negative errno, or zero on success
 *
 * Success happens when the "mask" bits have the specified value (hardware
 * handshake done).  There are two failure modes:  "usec" have passed (major
 * hardware flakeout), or the register reads as all-ones (hardware removed).
 *
 * That last failure should_only happen in cases like physical cardbus eject
 * before driver shutdown. But it also seems to be caused by bugs in cardbus
 * bridge shutdown:  shutting down the bridge before the devices using it.
 */
static int handshake (u32 *ptr, u32 mask, u32 done, int usec)
{
        u32     result;

        do {
                result = readl (ptr);
                if (result == ~(u32)0)          /* card removed */
                        return -ENODEV;
                result &= mask;
                if (result == done)
                        return 0;
                udelay (1);
                usec--;
        } while (usec > 0);
        return -ETIMEDOUT;
}

/*
 * hc states include: unknown, halted, ready, running
 * transitional states are messy just now
 * trying to avoid "running" unless urbs are active
 * a "ready" hc can be finishing prefetched work
 */

/* force HC to halt state from unknown (EHCI spec section 2.3) */
static int ehci_halt (struct ehci_hcd *ehci)
{
        u32     temp = readl (&ehci->regs->status);

        if ((temp & STS_HALT) != 0)
                return 0;

        temp = readl (&ehci->regs->command);
        temp &= ~CMD_RUN;
        writel (temp, &ehci->regs->command);
        return handshake (&ehci->regs->status, STS_HALT, STS_HALT, 16 * 125);
}

/* reset a non-running (STS_HALT == 1) controller */
static int ehci_reset (struct ehci_hcd *ehci)
{
        u32     command = readl (&ehci->regs->command);

        command |= CMD_RESET;
        dbg_cmd (ehci, "reset", command);
        writel (command, &ehci->regs->command);
        ehci->hcd.state = USB_STATE_HALT;
        return handshake (&ehci->regs->command, CMD_RESET, 0, 250 * 1000);
}

/* idle the controller (from running) */
static void ehci_ready (struct ehci_hcd *ehci)
{
        u32     temp;

#ifdef DEBUG
        if (!HCD_IS_RUNNING (ehci->hcd.state))
                BUG ();
#endif

        /* wait for any schedule enables/disables to take effect */
        temp = 0;
        if (ehci->async->qh_next.qh)
                temp = STS_ASS;
        if (ehci->next_uframe != -1)
                temp |= STS_PSS;
        if (handshake (&ehci->regs->status, STS_ASS | STS_PSS,
                                temp, 16 * 125) != 0) {
                ehci->hcd.state = USB_STATE_HALT;
                return;
        }

        /* then disable anything that's still active */
        temp = readl (&ehci->regs->command);
        temp &= ~(CMD_ASE | CMD_IAAD | CMD_PSE);
        writel (temp, &ehci->regs->command);

        /* hardware can take 16 microframes to turn off ... */
        if (handshake (&ehci->regs->status, STS_ASS | STS_PSS,
                                0, 16 * 125) != 0) {
                ehci->hcd.state = USB_STATE_HALT;
                return;
        }
}

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

#include "ehci-hub.c"
#include "ehci-mem.c"
#include "ehci-q.c"
#include "ehci-sched.c"

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

static void ehci_work(struct ehci_hcd *ehci, struct pt_regs *regs);

static void ehci_watchdog (unsigned long param)
{
        struct ehci_hcd         *ehci = (struct ehci_hcd *) param;
        unsigned long           flags;

        spin_lock_irqsave (&ehci->lock, flags);

        /* lost IAA irqs wedge things badly; seen with a vt8235 */
        if (ehci->reclaim) {
                u32             status = readl (&ehci->regs->status);

                if (status & STS_IAA) {
                        ehci_vdbg (ehci, "lost IAA\n");
                        COUNT (ehci->stats.lost_iaa);
                        writel (STS_IAA, &ehci->regs->status);
                        ehci->reclaim_ready = 1;
                }
        }

        /* stop async processing after it's idled a bit */
        if (test_bit (TIMER_ASYNC_OFF, &ehci->actions))
                start_unlink_async (ehci, ehci->async);

        /* ehci could run by timer, without IRQs ... */
        ehci_work (ehci, NULL);

        spin_unlock_irqrestore (&ehci->lock, flags);
}

/* EHCI 0.96 (and later) section 5.1 says how to kick BIOS/SMM/...
 * off the controller (maybe it can boot from highspeed USB disks).
 */
static int bios_handoff (struct ehci_hcd *ehci, int where, u32 cap)
{
        if (cap & (1 << 16)) {
                int msec = 500;

                /* request handoff to OS */
                cap &= 1 << 24;
                pci_write_config_dword (ehci->hcd.pdev, where, cap);

                /* and wait a while for it to happen */
                do {
                        wait_ms (10);
                        msec -= 10;
                        pci_read_config_dword (ehci->hcd.pdev, where, &cap);
                } while ((cap & (1 << 16)) && msec);
                if (cap & (1 << 16)) {
                        ehci_err (ehci, "BIOS handoff failed (%d, %04x)\n",
                                where, cap);
                        return 1;
                }
                ehci_dbg (ehci, "BIOS handoff succeeded\n");
        }
        return 0;
}

static int
ehci_reboot (struct notifier_block *self, unsigned long code, void *null)
{
        struct ehci_hcd         *ehci;

        ehci = container_of (self, struct ehci_hcd, reboot_notifier);

        /* make BIOS/etc use companion controller during reboot */
        writel (0, &ehci->regs->configured_flag);
        return 0;
}


/* called by khubd or root hub init threads */

static int ehci_hc_reset (struct usb_hcd *hcd)
{
        struct ehci_hcd         *ehci = hcd_to_ehci (hcd);
        u32                     temp;

        spin_lock_init (&ehci->lock);

        ehci->caps = (struct ehci_caps *) hcd->regs;
        ehci->regs = (struct ehci_regs *) (hcd->regs +
                                readb (&ehci->caps->length));
        dbg_hcs_params (ehci, "reset");
        dbg_hcc_params (ehci, "reset");

        /* EHCI 0.96 and later may have "extended capabilities" */
        temp = HCC_EXT_CAPS (readl (&ehci->caps->hcc_params));
        while (temp) {
                u32             cap;

                pci_read_config_dword (ehci->hcd.pdev, temp, &cap);
                ehci_dbg (ehci, "capability %04x at %02x\n", cap, temp);
                switch (cap & 0xff) {
                case 1:                 /* BIOS/SMM/... handoff */
                        if (bios_handoff (ehci, temp, cap) != 0)
                                return -EOPNOTSUPP;
                        break;
                case 0:                 /* illegal reserved capability */
                        ehci_warn (ehci, "illegal capability!\n");
                        cap = 0;
                        /* FALLTHROUGH */
                default:                /* unknown */
                        break;
                }
                temp = (cap >> 8) & 0xff;
        }

        /* cache this readonly data; minimize PCI reads */
        ehci->hcs_params = readl (&ehci->caps->hcs_params);

        /* force HC to halt state */
        return ehci_halt (ehci);
}

static int ehci_start (struct usb_hcd *hcd)
{
        struct ehci_hcd         *ehci = hcd_to_ehci (hcd);
        u32                     temp;
        struct usb_device       *udev;
        struct usb_bus          *bus;
        int                     retval;
        u32                     hcc_params;
        u8                      tempbyte;

        /*
         * hw default: 1K periodic list heads, one per frame.
         * periodic_size can shrink by USBCMD update if hcc_params allows.
         */
        ehci->periodic_size = DEFAULT_I_TDPS;
        if ((retval = ehci_mem_init (ehci, SLAB_KERNEL)) < 0)
                return retval;

        /* controllers may cache some of the periodic schedule ... */
        hcc_params = readl (&ehci->caps->hcc_params);
        if (HCC_ISOC_CACHE (hcc_params))        // full frame cache
                ehci->i_thresh = 8;
        else                                    // N microframes cached
                ehci->i_thresh = 2 + HCC_ISOC_THRES (hcc_params);

        ehci->reclaim = 0;
        ehci->next_uframe = -1;

        /* controller state:  unknown --> reset */

        /* EHCI spec section 4.1 */
        if ((retval = ehci_reset (ehci)) != 0) {
                ehci_mem_cleanup (ehci);
                return retval;
        }
        writel (INTR_MASK, &ehci->regs->intr_enable);
        writel (ehci->periodic_dma, &ehci->regs->frame_list);

        /*
         * dedicate a qh for the async ring head, since we couldn't unlink
         * a 'real' qh without stopping the async schedule [4.8].  use it
         * as the 'reclamation list head' too.
         * its dummy is used in hw_alt_next of many tds, to prevent the qh
         * from automatically advancing to the next td after short reads.
         */
        ehci->async->qh_next.qh = 0;
        ehci->async->hw_next = QH_NEXT (ehci->async->qh_dma);
        ehci->async->hw_info1 = cpu_to_le32 (QH_HEAD);
        ehci->async->hw_token = cpu_to_le32 (QTD_STS_HALT);
        ehci->async->hw_qtd_next = EHCI_LIST_END;
        ehci->async->qh_state = QH_STATE_LINKED;
        ehci->async->hw_alt_next = QTD_NEXT (ehci->async->dummy->qtd_dma);
        writel ((u32)ehci->async->qh_dma, &ehci->regs->async_next);

        /*
         * hcc_params controls whether ehci->regs->segment must (!!!)
         * be used; it constrains QH/ITD/SITD and QTD locations.
         * pci_pool consistent memory always uses segment zero.
         * streaming mappings for I/O buffers, like pci_map_single(),
         * can return segments above 4GB, if the device allows.
         *
         * NOTE:  the dma mask is visible through dma_supported(), so
         * drivers can pass this info along ... like NETIF_F_HIGHDMA,
         * Scsi_Host.highmem_io, and so forth.  It's readonly to all
         * host side drivers though.
         */
        if (HCC_64BIT_ADDR (hcc_params)) {
                writel (0, &ehci->regs->segment);
#if 0
// this is deeply broken on almost all architectures
                if (!pci_set_dma_mask (ehci->hcd.pdev, 0xffffffffffffffffULL))
                        ehci_info (ehci, "enabled 64bit PCI DMA\n");
#endif
        }

        /* help hc dma work well with cachelines */
        pci_set_mwi (ehci->hcd.pdev);

        /* clear interrupt enables, set irq latency */
        temp = readl (&ehci->regs->command) & 0x0fff;
        if (log2_irq_thresh < 0 || log2_irq_thresh > 6)
                log2_irq_thresh = 0;
        temp |= 1 << (16 + log2_irq_thresh);
        // if hc can park (ehci >= 0.96), default is 3 packets per async QH
        if (HCC_PGM_FRAMELISTLEN (hcc_params)) {
                /* periodic schedule size can be smaller than default */
                temp &= ~(3 << 2);
                temp |= (EHCI_TUNE_FLS << 2);
                switch (EHCI_TUNE_FLS) {
                case 0: ehci->periodic_size = 1024; break;
                case 1: ehci->periodic_size = 512; break;
                case 2: ehci->periodic_size = 256; break;
                default:        BUG ();
                }
        }
        temp &= ~(CMD_IAAD | CMD_ASE | CMD_PSE),
        // Philips, Intel, and maybe others need CMD_RUN before the
        // root hub will detect new devices (why?); NEC doesn't
        temp |= CMD_RUN;
        writel (temp, &ehci->regs->command);
        dbg_cmd (ehci, "init", temp);

        /* set async sleep time = 10 us ... ? */

        init_timer (&ehci->watchdog);
        ehci->watchdog.function = ehci_watchdog;
        ehci->watchdog.data = (unsigned long) ehci;

        /* wire up the root hub */
        bus = hcd_to_bus (hcd);
        bus->root_hub = udev = usb_alloc_dev (NULL, bus);
        if (!udev) {
done2:
                ehci_mem_cleanup (ehci);
                return -ENOMEM;
        }

        /*
         * Start, enabling full USB 2.0 functionality ... usb 1.1 devices
         * are explicitly handed to companion controller(s), so no TT is
         * involved with the root hub.
         */
        ehci->reboot_notifier.notifier_call = ehci_reboot;
//      register_reboot_notifier (&ehci->reboot_notifier);

        ehci->hcd.state = USB_STATE_RUNNING;
        writel (FLAG_CF, &ehci->regs->configured_flag);
        readl (&ehci->regs->command);   /* unblock posted write */

        /* PCI Serial Bus Release Number is at 0x60 offset */
        pci_read_config_byte (hcd->pdev, 0x60, &tempbyte);
        temp = readw (&ehci->caps->hci_version);
        ehci_info (ehci,
                "USB %x.%x enabled, EHCI %x.%02x, driver %s\n",
                ((tempbyte & 0xf0)>>4), (tempbyte & 0x0f),
                temp >> 8, temp & 0xff, DRIVER_VERSION);

        /*
         * From here on, khubd concurrently accesses the root
         * hub; drivers will be talking to enumerated devices.
         *
         * Before this point the HC was idle/ready.  After, khubd
         * and device drivers may start it running.
         */
        udev->speed = USB_SPEED_HIGH;
        if (hcd_register_root (hcd) != 0) {
                if (hcd->state == USB_STATE_RUNNING)
                        ehci_ready (ehci);
                ehci_reset (ehci);
                bus->root_hub = 0;
                usb_put_dev (udev);
                retval = -ENODEV;
                goto done2;
        }

        create_debug_files (ehci);

        return 0;
}

/* always called by thread; normally rmmod */

static void ehci_stop (struct usb_hcd *hcd)
{
        struct ehci_hcd         *ehci = hcd_to_ehci (hcd);

        ehci_dbg (ehci, "stop\n");

        /* no more interrupts ... */
        if (hcd->state == USB_STATE_RUNNING)
                ehci_ready (ehci);
        if (in_interrupt ()) {          /* must not happen!! */
                ehci_err (ehci, "stopped in_interrupt!\n");
                return;
        }
        del_timer_sync (&ehci->watchdog);
        ehci_reset (ehci);

        /* let companion controllers work when we aren't */
        writel (0, &ehci->regs->configured_flag);
//      unregister_reboot_notifier (&ehci->reboot_notifier);

        remove_debug_files (ehci);

        /* root hub is shut down separately (first, when possible) */
        spin_lock_irq (&ehci->lock);
        ehci_work (ehci, NULL);
        spin_unlock_irq (&ehci->lock);
        ehci_mem_cleanup (ehci);

#ifdef  EHCI_STATS
        ehci_dbg (ehci, "irq normal %ld err %ld reclaim %ld (lost %ld)\n",
                ehci->stats.normal, ehci->stats.error, ehci->stats.reclaim,
                ehci->stats.lost_iaa);
        ehci_dbg (ehci, "complete %ld unlink %ld\n",
                ehci->stats.complete, ehci->stats.unlink);
#endif

        dbg_status (ehci, "ehci_stop completed", readl (&ehci->regs->status));
}

static int ehci_get_frame (struct usb_hcd *hcd)
{
        struct ehci_hcd         *ehci = hcd_to_ehci (hcd);
        return (readl (&ehci->regs->frame_index) >> 3) % ehci->periodic_size;
}

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

#ifdef  CONFIG_PM

/* suspend/resume, section 4.3 */

static int ehci_suspend (struct usb_hcd *hcd, u32 state)
{
        struct ehci_hcd         *ehci = hcd_to_ehci (hcd);
        int                     ports;
        int                     i;

        ehci_dbg (ehci, "suspend to %d\n", state);

        ports = HCS_N_PORTS (ehci->hcs_params);

        // FIXME:  This assumes what's probably a D3 level suspend...

        // FIXME:  usb wakeup events on this bus should resume the machine.
        // pci config register PORTWAKECAP controls which ports can do it;
        // bios may have initted the register...

        /* suspend each port, then stop the hc */
        for (i = 0; i < ports; i++) {
                int     temp = readl (&ehci->regs->port_status [i]);

                if ((temp & PORT_PE) == 0
                                || (temp & PORT_OWNER) != 0)
                        continue;
                ehci_dbg (ehci, "suspend port %d", i);
                temp |= PORT_SUSPEND;
                writel (temp, &ehci->regs->port_status [i]);
        }

        if (hcd->state == USB_STATE_RUNNING)
                ehci_ready (ehci);
        writel (readl (&ehci->regs->command) & ~CMD_RUN, &ehci->regs->command);

// save pci FLADJ value

        /* who tells PCI to reduce power consumption? */

        return 0;
}

static int ehci_resume (struct usb_hcd *hcd)
{
        struct ehci_hcd         *ehci = hcd_to_ehci (hcd);
        int                     ports;
        int                     i;

        ehci_dbg (ehci, "resume\n");

        ports = HCS_N_PORTS (ehci->hcs_params);

        // FIXME:  if controller didn't retain state,
        // return and let generic code clean it up
        // test configured_flag ?

        /* resume HC and each port */
// restore pci FLADJ value
        // khubd and drivers will set HC running, if needed;
        hcd->state = USB_STATE_RUNNING;
        // FIXME Philips/Intel/... etc don't really have a "READY"
        // state ... turn on CMD_RUN too
        for (i = 0; i < ports; i++) {
                int     temp = readl (&ehci->regs->port_status [i]);

                if ((temp & PORT_PE) == 0
                                || (temp & PORT_SUSPEND) != 0)
                        continue;
                ehci_dbg (ehci, "resume port %d", i);
                temp |= PORT_RESUME;
                writel (temp, &ehci->regs->port_status [i]);
                readl (&ehci->regs->command);   /* unblock posted writes */

                wait_ms (20);
                temp &= ~PORT_RESUME;
                writel (temp, &ehci->regs->port_status [i]);
        }
        readl (&ehci->regs->command);   /* unblock posted writes */
        return 0;
}

#endif

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

/*
 * ehci_work is called from some interrupts, timers, and so on.
 * it calls driver completion functions, after dropping ehci->lock.
 */
static void ehci_work (struct ehci_hcd *ehci, struct pt_regs *regs)
{
        timer_action_done (ehci, TIMER_IO_WATCHDOG);
        if (ehci->reclaim_ready)
                end_unlink_async (ehci, regs);
        scan_async (ehci, regs);
        if (ehci->next_uframe != -1)
                scan_periodic (ehci, regs);

        /* the IO watchdog guards against hardware or driver bugs that
         * misplace IRQs, and should let us run completely without IRQs.
         */
        if ((ehci->async->qh_next.ptr != 0) || (ehci->periodic_sched != 0))
                timer_action (ehci, TIMER_IO_WATCHDOG);
}

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

static void ehci_irq (struct usb_hcd *hcd, struct pt_regs *regs)
{
        struct ehci_hcd         *ehci = hcd_to_ehci (hcd);
        u32                     status;
        int                     bh;

        spin_lock (&ehci->lock);

        status = readl (&ehci->regs->status);

        /* e.g. cardbus physical eject */
        if (status == ~(u32) 0) {
                ehci_dbg (ehci, "device removed\n");
                goto dead;
        }

        status &= INTR_MASK;
        if (!status)                    /* irq sharing? */
                goto done;

        /* clear (just) interrupts */
        writel (status, &ehci->regs->status);
        readl (&ehci->regs->command);   /* unblock posted write */
        bh = 0;

#ifdef  EHCI_VERBOSE_DEBUG
        /* unrequested/ignored: Port Change Detect, Frame List Rollover */
        dbg_status (ehci, "irq", status);
#endif

        /* INT, ERR, and IAA interrupt rates can be throttled */

        /* normal [4.15.1.2] or error [4.15.1.1] completion */
        if (likely ((status & (STS_INT|STS_ERR)) != 0)) {
                if (likely ((status & STS_ERR) == 0))
                        COUNT (ehci->stats.normal);
                else
                        COUNT (ehci->stats.error);
                bh = 1;
        }

        /* complete the unlinking of some qh [4.15.2.3] */
        if (status & STS_IAA) {
                COUNT (ehci->stats.reclaim);
                ehci->reclaim_ready = 1;
                bh = 1;
        }

        /* PCI errors [4.15.2.4] */
        if (unlikely ((status & STS_FATAL) != 0)) {
                ehci_err (ehci, "fatal error\n");
dead:
                ehci_reset (ehci);
                /* generic layer kills/unlinks all urbs, then
                 * uses ehci_stop to clean up the rest
                 */
                bh = 1;
        }

        if (bh)
                ehci_work (ehci, regs);
done:
        spin_unlock (&ehci->lock);
}

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

/*
 * non-error returns are a promise to giveback() the urb later
 * we drop ownership so next owner (or urb unlink) can get it
 *
 * urb + dev is in hcd_dev.urb_list
 * we're queueing TDs onto software and hardware lists
 *
 * hcd-specific init for hcpriv hasn't been done yet
 *
 * NOTE:  control, bulk, and interrupt share the same code to append TDs
 * to a (possibly active) QH, and the same QH scanning code.
 */
static int ehci_urb_enqueue (
        struct usb_hcd  *hcd,
        struct urb      *urb,
        int             mem_flags
) {
        struct ehci_hcd         *ehci = hcd_to_ehci (hcd);
        struct list_head        qtd_list;

        urb->transfer_flags &= ~EHCI_STATE_UNLINK;
        INIT_LIST_HEAD (&qtd_list);

        switch (usb_pipetype (urb->pipe)) {
        // case PIPE_CONTROL:
        // case PIPE_BULK:
        default:
                if (!qh_urb_transaction (ehci, urb, &qtd_list, mem_flags))
                        return -ENOMEM;
                return submit_async (ehci, urb, &qtd_list, mem_flags);

        case PIPE_INTERRUPT:
                if (!qh_urb_transaction (ehci, urb, &qtd_list, mem_flags))
                        return -ENOMEM;
                return intr_submit (ehci, urb, &qtd_list, mem_flags);

        case PIPE_ISOCHRONOUS:
                if (urb->dev->speed == USB_SPEED_HIGH)
                        return itd_submit (ehci, urb, mem_flags);
#ifdef have_split_iso
                else
                        return sitd_submit (ehci, urb, mem_flags);
#else
                dbg ("no split iso support yet");
                return -ENOSYS;
#endif /* have_split_iso */
        }
}

/* remove from hardware lists
 * completions normally happen asynchronously
 */

static int ehci_urb_dequeue (struct usb_hcd *hcd, struct urb *urb)
{
        struct ehci_hcd         *ehci = hcd_to_ehci (hcd);
        struct ehci_qh          *qh;
        unsigned long           flags;

        spin_lock_irqsave (&ehci->lock, flags);
        switch (usb_pipetype (urb->pipe)) {
        // case PIPE_CONTROL:
        // case PIPE_BULK:
        default:
                qh = (struct ehci_qh *) urb->hcpriv;
                if (!qh)
                        break;

                /* if we need to use IAA and it's busy, defer */
                if (qh->qh_state == QH_STATE_LINKED
                                && ehci->reclaim
                                && HCD_IS_RUNNING (ehci->hcd.state)
                                ) {
                        struct ehci_qh          *last;

                        for (last = ehci->reclaim;
                                        last->reclaim;
                                        last = last->reclaim)
                                continue;
                        qh->qh_state = QH_STATE_UNLINK_WAIT;
                        last->reclaim = qh;

                /* bypass IAA if the hc can't care */
                } else if (!HCD_IS_RUNNING (ehci->hcd.state) && ehci->reclaim)
                        end_unlink_async (ehci, NULL);

                /* something else might have unlinked the qh by now */
                if (qh->qh_state == QH_STATE_LINKED)
                        start_unlink_async (ehci, qh);
                break;

        case PIPE_INTERRUPT:
                qh = (struct ehci_qh *) urb->hcpriv;
                if (!qh)
                        break;
                if (qh->qh_state == QH_STATE_LINKED) {
                        /* messy, can spin or block a microframe ... */
                        intr_deschedule (ehci, qh, 1);
                        /* qh_state == IDLE */
                }
                qh_completions (ehci, qh, NULL);

                /* reschedule QH iff another request is queued */
                if (!list_empty (&qh->qtd_list)
                                && HCD_IS_RUNNING (ehci->hcd.state)) {
                        int status;

                        status = qh_schedule (ehci, qh);
                        spin_unlock_irqrestore (&ehci->lock, flags);

                        if (status != 0) {
                                // shouldn't happen often, but ...
                                // FIXME kill those tds' urbs
                                err ("can't reschedule qh %p, err %d",
                                        qh, status);
                        }
                        return status;
                }
                break;

        case PIPE_ISOCHRONOUS:
                // itd or sitd ...

                // wait till next completion, do it then.
                // completion irqs can wait up to 1024 msec,
                urb->transfer_flags |= EHCI_STATE_UNLINK;
                break;
        }
        spin_unlock_irqrestore (&ehci->lock, flags);
        return 0;
}

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

// bulk qh holds the data toggle

static void
ehci_endpoint_disable (struct usb_hcd *hcd, struct hcd_dev *dev, int ep)
{
        struct ehci_hcd         *ehci = hcd_to_ehci (hcd);
        int                     epnum;
        unsigned long           flags;
        struct ehci_qh          *qh;

        /* ASSERT:  any requests/urbs are being unlinked */
        /* ASSERT:  nobody can be submitting urbs for this any more */

        epnum = ep & USB_ENDPOINT_NUMBER_MASK;
        if (epnum != 0 && (ep & USB_DIR_IN))
                epnum |= 0x10;

rescan:
        spin_lock_irqsave (&ehci->lock, flags);
        qh = (struct ehci_qh *) dev->ep [epnum];
        if (!qh)
                goto done;

        if (!HCD_IS_RUNNING (ehci->hcd.state))
                qh->qh_state = QH_STATE_IDLE;
        switch (qh->qh_state) {
        case QH_STATE_UNLINK:           /* wait for hw to finish? */
                spin_unlock_irqrestore (&ehci->lock, flags);
                set_current_state (TASK_UNINTERRUPTIBLE);
                schedule_timeout (1);
                goto rescan;
        case QH_STATE_IDLE:             /* fully unlinked */
                if (list_empty (&qh->qtd_list)) {
                        qh_put (ehci, qh);
                        break;
                }
                /* else FALL THROUGH */
        default:
                /* caller was supposed to have unlinked any requests;
                 * that's not our job.  just leak this memory.
                 */
                ehci_err (ehci, "qh %p (#%d) state %d%s\n",
                        qh, epnum, qh->qh_state,
                        list_empty (&qh->qtd_list) ? "" : "(has tds)");
                break;
        }
        dev->ep [epnum] = 0;
done:
        spin_unlock_irqrestore (&ehci->lock, flags);
        return;
}

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

static const struct hc_driver ehci_driver = {
        .description =          hcd_name,

        /*
         * generic hardware linkage
         */
        .irq =                  ehci_irq,
        .flags =                HCD_MEMORY | HCD_USB2,

        /*
         * basic lifecycle operations
         */
        .reset =                ehci_hc_reset,
        .start =                ehci_start,
#ifdef  CONFIG_PM
        .suspend =              ehci_suspend,
        .resume =               ehci_resume,
#endif
        .stop =                 ehci_stop,

        /*
         * memory lifecycle (except per-request)
         */
        .hcd_alloc =            ehci_hcd_alloc,
        .hcd_free =             ehci_hcd_free,

        /*
         * managing i/o requests and associated device resources
         */
        .urb_enqueue =          ehci_urb_enqueue,
        .urb_dequeue =          ehci_urb_dequeue,
        .endpoint_disable =     ehci_endpoint_disable,

        /*
         * scheduling support
         */
        .get_frame_number =     ehci_get_frame,

        /*
         * root hub support
         */
        .hub_status_data =      ehci_hub_status_data,
        .hub_control =          ehci_hub_control,
};

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

/* EHCI spec says PCI is required. */

/* PCI driver selection metadata; PCI hotplugging uses this */
static const struct pci_device_id pci_ids [] = { {
        /* handle any USB 2.0 EHCI controller */
        PCI_DEVICE_CLASS(((PCI_CLASS_SERIAL_USB << 8) | 0x20), ~0),
        .driver_data =  (unsigned long) &ehci_driver,
        },
        { /* end: all zeroes */ }
};
MODULE_DEVICE_TABLE (pci, pci_ids);

/* pci driver glue; this is a "new style" PCI driver module */
static struct pci_driver ehci_pci_driver = {
        .name =         (char *) hcd_name,
        .id_table =     pci_ids,

        .probe =        usb_hcd_pci_probe,
        .remove =       usb_hcd_pci_remove,

#ifdef  CONFIG_PM
        .suspend =      usb_hcd_pci_suspend,
        .resume =       usb_hcd_pci_resume,
#endif
};

#define DRIVER_INFO DRIVER_VERSION " " DRIVER_DESC

MODULE_DESCRIPTION (DRIVER_INFO);
MODULE_AUTHOR (DRIVER_AUTHOR);
MODULE_LICENSE ("GPL");

/*static*/ int __init ehci_hcd_init (void)
{
        if (usb_disabled())
                return -ENODEV;

        pr_debug ("%s: block sizes: qh %Zd qtd %Zd itd %Zd sitd %Zd\n",
                hcd_name,
                sizeof (struct ehci_qh), sizeof (struct ehci_qtd),
                sizeof (struct ehci_itd), sizeof (struct ehci_sitd));

        return pci_module_init (&ehci_pci_driver);
}
//module_init (init);

/*static*/ void __exit ehci_hcd_cleanup (void)
{      
        pci_unregister_driver (&ehci_pci_driver);
}
//module_exit (cleanup);