/*
 * MUSB OTG peripheral driver ep0 handling
 *
 * Copyright 2005 Mentor Graphics Corporation
 * Copyright (C) 2005-2006 by Texas Instruments
 * Copyright (C) 2006-2007 Nokia Corporation
 * Copyright (C) 2008-2009 MontaVista Software, Inc. <source@mvista.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 * 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., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA
 *
 * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN
 * NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/timer.h>
#include <linux/spinlock.h>
#include <linux/device.h>
#include <linux/interrupt.h>

#include "musb_core.h"

/* ep0 is always musb->endpoints[0].ep_in */
#define next_ep0_request(musb)  next_in_request(&(musb)->endpoints[0])

/*
 * locking note:  we use only the controller lock, for simpler correctness.
 * It's always held with IRQs blocked.
 *
 * It protects the ep0 request queue as well as ep0_state, not just the
 * controller and indexed registers.  And that lock stays held unless it
 * needs to be dropped to allow reentering this driver ... like upcalls to
 * the gadget driver, or adjusting endpoint halt status.
 */

static char *decode_ep0stage(u8 stage)
{
        switch (stage) {
        case MUSB_EP0_STAGE_IDLE:       return "idle";
        case MUSB_EP0_STAGE_SETUP:      return "setup";
        case MUSB_EP0_STAGE_TX:         return "in";
        case MUSB_EP0_STAGE_RX:         return "out";
        case MUSB_EP0_STAGE_ACKWAIT:    return "wait";
        case MUSB_EP0_STAGE_STATUSIN:   return "in/status";
        case MUSB_EP0_STAGE_STATUSOUT:  return "out/status";
        default:                        return "?";
        }
}

/* handle a standard GET_STATUS request
 * Context:  caller holds controller lock
 */
static int service_tx_status_request(
        struct musb *musb,
        const struct usb_ctrlrequest *ctrlrequest)
{
        void __iomem    *mbase = musb->mregs;
        int handled = 1;
        u8 result[2], epnum = 0;
        const u8 recip = ctrlrequest->bRequestType & USB_RECIP_MASK;

        result[1] = 0;

        switch (recip) {
        case USB_RECIP_DEVICE:
                result[0] = musb->g.is_selfpowered << USB_DEVICE_SELF_POWERED;
                result[0] |= musb->may_wakeup << USB_DEVICE_REMOTE_WAKEUP;
                if (musb->g.is_otg) {
                        result[0] |= musb->g.b_hnp_enable
                                << USB_DEVICE_B_HNP_ENABLE;
                        result[0] |= musb->g.a_alt_hnp_support
                                << USB_DEVICE_A_ALT_HNP_SUPPORT;
                        result[0] |= musb->g.a_hnp_support
                                << USB_DEVICE_A_HNP_SUPPORT;
                }
                break;

        case USB_RECIP_INTERFACE:
                result[0] = 0;
                break;

        case USB_RECIP_ENDPOINT: {
                int             is_in;
                struct musb_ep  *ep;
                u16             tmp;
                void __iomem    *regs;

                epnum = (u8) ctrlrequest->wIndex;
                if (!epnum) {
                        result[0] = 0;
                        break;
                }

                is_in = epnum & USB_DIR_IN;
                if (is_in) {
                        epnum &= 0x0f;
                        ep = &musb->endpoints[epnum].ep_in;
                } else {
                        ep = &musb->endpoints[epnum].ep_out;
                }
                regs = musb->endpoints[epnum].regs;

                if (epnum >= MUSB_C_NUM_EPS || !ep->desc) {
                        handled = -EINVAL;
                        break;
                }

                musb_ep_select(mbase, epnum);
                if (is_in)
                        tmp = musb_readw(regs, MUSB_TXCSR)
                                                & MUSB_TXCSR_P_SENDSTALL;
                else
                        tmp = musb_readw(regs, MUSB_RXCSR)
                                                & MUSB_RXCSR_P_SENDSTALL;
                musb_ep_select(mbase, 0);

                result[0] = tmp ? 1 : 0;
                } break;

        default:
                /* class, vendor, etc ... delegate */
                handled = 0;
                break;
        }

        /* fill up the fifo; caller updates csr0 */
        if (handled > 0) {
                u16     len = le16_to_cpu(ctrlrequest->wLength);

                if (len > 2)
                        len = 2;
                musb_write_fifo(&musb->endpoints[0], len, result);
        }

        return handled;
}

/*
 * handle a control-IN request, the end0 buffer contains the current request
 * that is supposed to be a standard control request. Assumes the fifo to
 * be at least 2 bytes long.
 *
 * @return 0 if the request was NOT HANDLED,
 * < 0 when error
 * > 0 when the request is processed
 *
 * Context:  caller holds controller lock
 */
static int
service_in_request(struct musb *musb, const struct usb_ctrlrequest *ctrlrequest)
{
        int handled = 0;        /* not handled */

        if ((ctrlrequest->bRequestType & USB_TYPE_MASK)
                        == USB_TYPE_STANDARD) {
                switch (ctrlrequest->bRequest) {
                case USB_REQ_GET_STATUS:
                        handled = service_tx_status_request(musb,
                                        ctrlrequest);
                        break;

                /* case USB_REQ_SYNC_FRAME: */

                default:
                        break;
                }
        }
        return handled;
}

/*
 * Context:  caller holds controller lock
 */
static void musb_g_ep0_giveback(struct musb *musb, struct usb_request *req)
{
        musb_g_giveback(&musb->endpoints[0].ep_in, req, 0);
}

/*
 * Tries to start B-device HNP negotiation if enabled via sysfs
 */
static inline void musb_try_b_hnp_enable(struct musb *musb)
{
        void __iomem    *mbase = musb->mregs;
        u8              devctl;

        dev_dbg(musb->controller, "HNP: Setting HR\n");
        devctl = musb_readb(mbase, MUSB_DEVCTL);
        musb_writeb(mbase, MUSB_DEVCTL, devctl | MUSB_DEVCTL_HR);
}

/*
 * Handle all control requests with no DATA stage, including standard
 * requests such as:
 * USB_REQ_SET_CONFIGURATION, USB_REQ_SET_INTERFACE, unrecognized
 *      always delegated to the gadget driver
 * USB_REQ_SET_ADDRESS, USB_REQ_CLEAR_FEATURE, USB_REQ_SET_FEATURE
 *      always handled here, except for class/vendor/... features
 *
 * Context:  caller holds controller lock
 */
static int
service_zero_data_request(struct musb *musb,
                struct usb_ctrlrequest *ctrlrequest)
__releases(musb->lock)
__acquires(musb->lock)
{
        int handled = -EINVAL;
        void __iomem *mbase = musb->mregs;
        const u8 recip = ctrlrequest->bRequestType & USB_RECIP_MASK;

        /* the gadget driver handles everything except what we MUST handle */
        if ((ctrlrequest->bRequestType & USB_TYPE_MASK)
                        == USB_TYPE_STANDARD) {
                switch (ctrlrequest->bRequest) {
                case USB_REQ_SET_ADDRESS:
                        /* change it after the status stage */
                        musb->set_address = true;
                        musb->address = (u8) (ctrlrequest->wValue & 0x7f);
                        handled = 1;
                        break;

                case USB_REQ_CLEAR_FEATURE:
                        switch (recip) {
                        case USB_RECIP_DEVICE:
                                if (ctrlrequest->wValue
                                                != USB_DEVICE_REMOTE_WAKEUP)
                                        break;
                                musb->may_wakeup = 0;
                                handled = 1;
                                break;
                        case USB_RECIP_INTERFACE:
                                break;
                        case USB_RECIP_ENDPOINT:{
                                const u8                epnum =
                                        ctrlrequest->wIndex & 0x0f;
                                struct musb_ep          *musb_ep;
                                struct musb_hw_ep       *ep;
                                struct musb_request     *request;
                                void __iomem            *regs;
                                int                     is_in;
                                u16                     csr;

                                if (epnum == 0 || epnum >= MUSB_C_NUM_EPS ||
                                    ctrlrequest->wValue != USB_ENDPOINT_HALT)
                                        break;

                                ep = musb->endpoints + epnum;
                                regs = ep->regs;
                                is_in = ctrlrequest->wIndex & USB_DIR_IN;
                                if (is_in)
                                        musb_ep = &ep->ep_in;
                                else
                                        musb_ep = &ep->ep_out;
                                if (!musb_ep->desc)
                                        break;

                                handled = 1;
                                /* Ignore request if endpoint is wedged */
                                if (musb_ep->wedged)
                                        break;

                                musb_ep_select(mbase, epnum);
                                if (is_in) {
                                        csr  = musb_readw(regs, MUSB_TXCSR);
                                        csr |= MUSB_TXCSR_CLRDATATOG |
                                               MUSB_TXCSR_P_WZC_BITS;
                                        csr &= ~(MUSB_TXCSR_P_SENDSTALL |
                                                 MUSB_TXCSR_P_SENTSTALL |
                                                 MUSB_TXCSR_TXPKTRDY);
                                        musb_writew(regs, MUSB_TXCSR, csr);
                                } else {
                                        csr  = musb_readw(regs, MUSB_RXCSR);
                                        csr |= MUSB_RXCSR_CLRDATATOG |
                                               MUSB_RXCSR_P_WZC_BITS;
                                        csr &= ~(MUSB_RXCSR_P_SENDSTALL |
                                                 MUSB_RXCSR_P_SENTSTALL);
                                        musb_writew(regs, MUSB_RXCSR, csr);
                                }

                                /* Maybe start the first request in the queue */
                                request = next_request(musb_ep);
                                if (!musb_ep->busy && request) {
                                        dev_dbg(musb->controller, "restarting the request\n");
                                        musb_ep_restart(musb, request);
                                }

                                /* select ep0 again */
                                musb_ep_select(mbase, 0);
                                } break;
                        default:
                                /* class, vendor, etc ... delegate */
                                handled = 0;
                                break;
                        }
                        break;

                case USB_REQ_SET_FEATURE:
                        switch (recip) {
                        case USB_RECIP_DEVICE:
                                handled = 1;
                                switch (ctrlrequest->wValue) {
                                case USB_DEVICE_REMOTE_WAKEUP:
                                        musb->may_wakeup = 1;
                                        break;
                                case USB_DEVICE_TEST_MODE:
                                        if (musb->g.speed != USB_SPEED_HIGH)
                                                goto stall;
                                        if (ctrlrequest->wIndex & 0xff)
                                                goto stall;

                                        switch (ctrlrequest->wIndex >> 8) {
                                        case 1:
                                                pr_debug("TEST_J\n");
                                                /* TEST_J */
                                                musb->test_mode_nr =
                                                        MUSB_TEST_J;
                                                break;
                                        case 2:
                                                /* TEST_K */
                                                pr_debug("TEST_K\n");
                                                musb->test_mode_nr =
                                                        MUSB_TEST_K;
                                                break;
                                        case 3:
                                                /* TEST_SE0_NAK */
                                                pr_debug("TEST_SE0_NAK\n");
                                                musb->test_mode_nr =
                                                        MUSB_TEST_SE0_NAK;
                                                break;
                                        case 4:
                                                /* TEST_PACKET */
                                                pr_debug("TEST_PACKET\n");
                                                musb->test_mode_nr =
                                                        MUSB_TEST_PACKET;
                                                break;

                                        case 0xc0:
                                                /* TEST_FORCE_HS */
                                                pr_debug("TEST_FORCE_HS\n");
                                                musb->test_mode_nr =
                                                        MUSB_TEST_FORCE_HS;
                                                break;
                                        case 0xc1:
                                                /* TEST_FORCE_FS */
                                                pr_debug("TEST_FORCE_FS\n");
                                                musb->test_mode_nr =
                                                        MUSB_TEST_FORCE_FS;
                                                break;
                                        case 0xc2:
                                                /* TEST_FIFO_ACCESS */
                                                pr_debug("TEST_FIFO_ACCESS\n");
                                                musb->test_mode_nr =
                                                        MUSB_TEST_FIFO_ACCESS;
                                                break;
                                        case 0xc3:
                                                /* TEST_FORCE_HOST */
                                                pr_debug("TEST_FORCE_HOST\n");
                                                musb->test_mode_nr =
                                                        MUSB_TEST_FORCE_HOST;
                                                break;
                                        default:
                                                goto stall;
                                        }

                                        /* enter test mode after irq */
                                        if (handled > 0)
                                                musb->test_mode = true;
                                        break;
                                case USB_DEVICE_B_HNP_ENABLE:
                                        if (!musb->g.is_otg)
                                                goto stall;
                                        musb->g.b_hnp_enable = 1;
                                        musb_try_b_hnp_enable(musb);
                                        break;
                                case USB_DEVICE_A_HNP_SUPPORT:
                                        if (!musb->g.is_otg)
                                                goto stall;
                                        musb->g.a_hnp_support = 1;
                                        break;
                                case USB_DEVICE_A_ALT_HNP_SUPPORT:
                                        if (!musb->g.is_otg)
                                                goto stall;
                                        musb->g.a_alt_hnp_support = 1;
                                        break;
                                case USB_DEVICE_DEBUG_MODE:
                                        handled = 0;
                                        break;
stall:
                                default:
                                        handled = -EINVAL;
                                        break;
                                }
                                break;

                        case USB_RECIP_INTERFACE:
                                break;

                        case USB_RECIP_ENDPOINT:{
                                const u8                epnum =
                                        ctrlrequest->wIndex & 0x0f;
                                struct musb_ep          *musb_ep;
                                struct musb_hw_ep       *ep;
                                void __iomem            *regs;
                                int                     is_in;
                                u16                     csr;

                                if (epnum == 0 || epnum >= MUSB_C_NUM_EPS ||
                                    ctrlrequest->wValue != USB_ENDPOINT_HALT)
                                        break;

                                ep = musb->endpoints + epnum;
                                regs = ep->regs;
                                is_in = ctrlrequest->wIndex & USB_DIR_IN;
                                if (is_in)
                                        musb_ep = &ep->ep_in;
                                else
                                        musb_ep = &ep->ep_out;
                                if (!musb_ep->desc)
                                        break;

                                musb_ep_select(mbase, epnum);
                                if (is_in) {
                                        csr = musb_readw(regs, MUSB_TXCSR);
                                        if (csr & MUSB_TXCSR_FIFONOTEMPTY)
                                                csr |= MUSB_TXCSR_FLUSHFIFO;
                                        csr |= MUSB_TXCSR_P_SENDSTALL
                                                | MUSB_TXCSR_CLRDATATOG
                                                | MUSB_TXCSR_P_WZC_BITS;
                                        musb_writew(regs, MUSB_TXCSR, csr);
                                } else {
                                        csr = musb_readw(regs, MUSB_RXCSR);
                                        csr |= MUSB_RXCSR_P_SENDSTALL
                                                | MUSB_RXCSR_FLUSHFIFO
                                                | MUSB_RXCSR_CLRDATATOG
                                                | MUSB_RXCSR_P_WZC_BITS;
                                        musb_writew(regs, MUSB_RXCSR, csr);
                                }

                                /* select ep0 again */
                                musb_ep_select(mbase, 0);
                                handled = 1;
                                } break;

                        default:
                                /* class, vendor, etc ... delegate */
                                handled = 0;
                                break;
                        }
                        break;
                default:
                        /* delegate SET_CONFIGURATION, etc */
                        handled = 0;
                }
        } else
                handled = 0;
        return handled;
}

/* we have an ep0out data packet
 * Context:  caller holds controller lock
 */
static void ep0_rxstate(struct musb *musb)
{
        void __iomem            *regs = musb->control_ep->regs;
        struct musb_request     *request;
        struct usb_request      *req;
        u16                     count, csr;

        request = next_ep0_request(musb);
        req = &request->request;

        /* read packet and ack; or stall because of gadget driver bug:
         * should have provided the rx buffer before setup() returned.
         */
        if (req) {
                void            *buf = req->buf + req->actual;
                unsigned        len = req->length - req->actual;

                /* read the buffer */
                count = musb_readb(regs, MUSB_COUNT0);
                if (count > len) {
                        req->status = -EOVERFLOW;
                        count = len;
                }
                if (count > 0) {
                        musb_read_fifo(&musb->endpoints[0], count, buf);
                        req->actual += count;
                }
                csr = MUSB_CSR0_P_SVDRXPKTRDY;
                if (count < 64 || req->actual == req->length) {
                        musb->ep0_state = MUSB_EP0_STAGE_STATUSIN;
                        csr |= MUSB_CSR0_P_DATAEND;
                } else
                        req = NULL;
        } else
                csr = MUSB_CSR0_P_SVDRXPKTRDY | MUSB_CSR0_P_SENDSTALL;


        /* Completion handler may choose to stall, e.g. because the
         * message just received holds invalid data.
         */
        if (req) {
                musb->ackpend = csr;
                musb_g_ep0_giveback(musb, req);
                if (!musb->ackpend)
                        return;
                musb->ackpend = 0;
        }
        musb_ep_select(musb->mregs, 0);
        musb_writew(regs, MUSB_CSR0, csr);
}

/*
 * transmitting to the host (IN), this code might be called from IRQ
 * and from kernel thread.
 *
 * Context:  caller holds controller lock
 */
static void ep0_txstate(struct musb *musb)
{
        void __iomem            *regs = musb->control_ep->regs;
        struct musb_request     *req = next_ep0_request(musb);
        struct usb_request      *request;
        u16                     csr = MUSB_CSR0_TXPKTRDY;
        u8                      *fifo_src;
        u8                      fifo_count;

        if (!req) {
                /* WARN_ON(1); */
                dev_dbg(musb->controller, "odd; csr0 %04x\n", musb_readw(regs, MUSB_CSR0));
                return;
        }

        request = &req->request;

        /* load the data */
        fifo_src = (u8 *) request->buf + request->actual;
        fifo_count = min((unsigned) MUSB_EP0_FIFOSIZE,
                request->length - request->actual);
        musb_write_fifo(&musb->endpoints[0], fifo_count, fifo_src);
        request->actual += fifo_count;

        /* update the flags */
        if (fifo_count < MUSB_MAX_END0_PACKET
                        || (request->actual == request->length
                                && !request->zero)) {
                musb->ep0_state = MUSB_EP0_STAGE_STATUSOUT;
                csr |= MUSB_CSR0_P_DATAEND;
        } else
                request = NULL;

        /* report completions as soon as the fifo's loaded; there's no
         * win in waiting till this last packet gets acked.  (other than
         * very precise fault reporting, needed by USB TMC; possible with
         * this hardware, but not usable from portable gadget drivers.)
         */
        if (request) {
                musb->ackpend = csr;
                musb_g_ep0_giveback(musb, request);
                if (!musb->ackpend)
                        return;
                musb->ackpend = 0;
        }

        /* send it out, triggering a "txpktrdy cleared" irq */
        musb_ep_select(musb->mregs, 0);
        musb_writew(regs, MUSB_CSR0, csr);
}

/*
 * Read a SETUP packet (struct usb_ctrlrequest) from the hardware.
 * Fields are left in USB byte-order.
 *
 * Context:  caller holds controller lock.
 */
static void
musb_read_setup(struct musb *musb, struct usb_ctrlrequest *req)
{
        struct musb_request     *r;
        void __iomem            *regs = musb->control_ep->regs;

        musb_read_fifo(&musb->endpoints[0], sizeof *req, (u8 *)req);

        /* NOTE:  earlier 2.6 versions changed setup packets to host
         * order, but now USB packets always stay in USB byte order.
         */
        dev_dbg(musb->controller, "SETUP req%02x.%02x v%04x i%04x l%d\n",
                req->bRequestType,
                req->bRequest,
                le16_to_cpu(req->wValue),
                le16_to_cpu(req->wIndex),
                le16_to_cpu(req->wLength));

        /* clean up any leftover transfers */
        r = next_ep0_request(musb);
        if (r)
                musb_g_ep0_giveback(musb, &r->request);

        /* For zero-data requests we want to delay the STATUS stage to
         * avoid SETUPEND errors.  If we read data (OUT), delay accepting
         * packets until there's a buffer to store them in.
         *
         * If we write data, the controller acts happier if we enable
         * the TX FIFO right away, and give the controller a moment
         * to switch modes...
         */
        musb->set_address = false;
        musb->ackpend = MUSB_CSR0_P_SVDRXPKTRDY;
        if (req->wLength == 0) {
                if (req->bRequestType & USB_DIR_IN)
                        musb->ackpend |= MUSB_CSR0_TXPKTRDY;
                musb->ep0_state = MUSB_EP0_STAGE_ACKWAIT;
        } else if (req->bRequestType & USB_DIR_IN) {
                musb->ep0_state = MUSB_EP0_STAGE_TX;
                musb_writew(regs, MUSB_CSR0, MUSB_CSR0_P_SVDRXPKTRDY);
                while ((musb_readw(regs, MUSB_CSR0)
                                & MUSB_CSR0_RXPKTRDY) != 0)
                        cpu_relax();
                musb->ackpend = 0;
        } else
                musb->ep0_state = MUSB_EP0_STAGE_RX;
}

static int
forward_to_driver(struct musb *musb, const struct usb_ctrlrequest *ctrlrequest)
__releases(musb->lock)
__acquires(musb->lock)
{
        int retval;
        if (!musb->gadget_driver)
                return -EOPNOTSUPP;
        spin_unlock(&musb->lock);
        retval = musb->gadget_driver->setup(&musb->g, ctrlrequest);
        spin_lock(&musb->lock);
        return retval;
}

/*
 * Handle peripheral ep0 interrupt
 *
 * Context: irq handler; we won't re-enter the driver that way.
 */
irqreturn_t musb_g_ep0_irq(struct musb *musb)
{
        u16             csr;
        u16             len;
        void __iomem    *mbase = musb->mregs;
        void __iomem    *regs = musb->endpoints[0].regs;
        irqreturn_t     retval = IRQ_NONE;

        musb_ep_select(mbase, 0);       /* select ep0 */
        csr = musb_readw(regs, MUSB_CSR0);
        len = musb_readb(regs, MUSB_COUNT0);

        dev_dbg(musb->controller, "csr %04x, count %d, ep0stage %s\n",
                        csr, len, decode_ep0stage(musb->ep0_state));

        if (csr & MUSB_CSR0_P_DATAEND) {
                /*
                 * If DATAEND is set we should not call the callback,
                 * hence the status stage is not complete.
                 */
                return IRQ_HANDLED;
        }

        /* I sent a stall.. need to acknowledge it now.. */
        if (csr & MUSB_CSR0_P_SENTSTALL) {
                musb_writew(regs, MUSB_CSR0,
                                csr & ~MUSB_CSR0_P_SENTSTALL);
                retval = IRQ_HANDLED;
                musb->ep0_state = MUSB_EP0_STAGE_IDLE;
                csr = musb_readw(regs, MUSB_CSR0);
        }

        /* request ended "early" */
        if (csr & MUSB_CSR0_P_SETUPEND) {
                musb_writew(regs, MUSB_CSR0, MUSB_CSR0_P_SVDSETUPEND);
                retval = IRQ_HANDLED;
                /* Transition into the early status phase */
                switch (musb->ep0_state) {
                case MUSB_EP0_STAGE_TX:
                        musb->ep0_state = MUSB_EP0_STAGE_STATUSOUT;
                        break;
                case MUSB_EP0_STAGE_RX:
                        musb->ep0_state = MUSB_EP0_STAGE_STATUSIN;
                        break;
                default:
                        ERR("SetupEnd came in a wrong ep0stage %s\n",
                            decode_ep0stage(musb->ep0_state));
                }
                csr = musb_readw(regs, MUSB_CSR0);
                /* NOTE:  request may need completion */
        }

        /* docs from Mentor only describe tx, rx, and idle/setup states.
         * we need to handle nuances around status stages, and also the
         * case where status and setup stages come back-to-back ...
         */
        switch (musb->ep0_state) {

        case MUSB_EP0_STAGE_TX:
                /* irq on clearing txpktrdy */
                if ((csr & MUSB_CSR0_TXPKTRDY) == 0) {
                        ep0_txstate(musb);
                        retval = IRQ_HANDLED;
                }
                break;

        case MUSB_EP0_STAGE_RX:
                /* irq on set rxpktrdy */
                if (csr & MUSB_CSR0_RXPKTRDY) {
                        ep0_rxstate(musb);
                        retval = IRQ_HANDLED;
                }
                break;

        case MUSB_EP0_STAGE_STATUSIN:
                /* end of sequence #2 (OUT/RX state) or #3 (no data) */

                /* update address (if needed) only @ the end of the
                 * status phase per usb spec, which also guarantees
                 * we get 10 msec to receive this irq... until this
                 * is done we won't see the next packet.
                 */
                if (musb->set_address) {
                        musb->set_address = false;
                        musb_writeb(mbase, MUSB_FADDR, musb->address);
                }

                /* enter test mode if needed (exit by reset) */
                else if (musb->test_mode) {
                        dev_dbg(musb->controller, "entering TESTMODE\n");

                        if (MUSB_TEST_PACKET == musb->test_mode_nr)
                                musb_load_testpacket(musb);

                        musb_writeb(mbase, MUSB_TESTMODE,
                                        musb->test_mode_nr);
                }
                /* FALLTHROUGH */

        case MUSB_EP0_STAGE_STATUSOUT:
                /* end of sequence #1: write to host (TX state) */
                {
                        struct musb_request     *req;

                        req = next_ep0_request(musb);
                        if (req)
                                musb_g_ep0_giveback(musb, &req->request);
                }

                /*
                 * In case when several interrupts can get coalesced,
                 * check to see if we've already received a SETUP packet...
                 */
                if (csr & MUSB_CSR0_RXPKTRDY)
                        goto setup;

                retval = IRQ_HANDLED;
                musb->ep0_state = MUSB_EP0_STAGE_IDLE;
                break;

        case MUSB_EP0_STAGE_IDLE:
                /*
                 * This state is typically (but not always) indiscernible
                 * from the status states since the corresponding interrupts
                 * tend to happen within too little period of time (with only
                 * a zero-length packet in between) and so get coalesced...
                 */
                retval = IRQ_HANDLED;
                musb->ep0_state = MUSB_EP0_STAGE_SETUP;
                /* FALLTHROUGH */

        case MUSB_EP0_STAGE_SETUP:
setup:
                if (csr & MUSB_CSR0_RXPKTRDY) {
                        struct usb_ctrlrequest  setup;
                        int                     handled = 0;

                        if (len != 8) {
                                ERR("SETUP packet len %d != 8 ?\n", len);
                                break;
                        }
                        musb_read_setup(musb, &setup);
                        retval = IRQ_HANDLED;

                        /* sometimes the RESET won't be reported */
                        if (unlikely(musb->g.speed == USB_SPEED_UNKNOWN)) {
                                u8      power;

                                printk(KERN_NOTICE "%s: peripheral reset "
                                                "irq lost!\n",
                                                musb_driver_name);
                                power = musb_readb(mbase, MUSB_POWER);
                                musb->g.speed = (power & MUSB_POWER_HSMODE)
                                        ? USB_SPEED_HIGH : USB_SPEED_FULL;

                        }

                        switch (musb->ep0_state) {

                        /* sequence #3 (no data stage), includes requests
                         * we can't forward (notably SET_ADDRESS and the
                         * device/endpoint feature set/clear operations)
                         * plus SET_CONFIGURATION and others we must
                         */
                        case MUSB_EP0_STAGE_ACKWAIT:
                                handled = service_zero_data_request(
                                                musb, &setup);

                                /*
                                 * We're expecting no data in any case, so
                                 * always set the DATAEND bit -- doing this
                                 * here helps avoid SetupEnd interrupt coming
                                 * in the idle stage when we're stalling...
                                 */
                                musb->ackpend |= MUSB_CSR0_P_DATAEND;

                                /* status stage might be immediate */
                                if (handled > 0)
                                        musb->ep0_state =
                                                MUSB_EP0_STAGE_STATUSIN;
                                break;

                        /* sequence #1 (IN to host), includes GET_STATUS
                         * requests that we can't forward, GET_DESCRIPTOR
                         * and others that we must
                         */
                        case MUSB_EP0_STAGE_TX:
                                handled = service_in_request(musb, &setup);
                                if (handled > 0) {
                                        musb->ackpend = MUSB_CSR0_TXPKTRDY
                                                | MUSB_CSR0_P_DATAEND;
                                        musb->ep0_state =
                                                MUSB_EP0_STAGE_STATUSOUT;
                                }
                                break;

                        /* sequence #2 (OUT from host), always forward */
                        default:                /* MUSB_EP0_STAGE_RX */
                                break;
                        }

                        dev_dbg(musb->controller, "handled %d, csr %04x, ep0stage %s\n",
                                handled, csr,
                                decode_ep0stage(musb->ep0_state));

                        /* unless we need to delegate this to the gadget
                         * driver, we know how to wrap this up:  csr0 has
                         * not yet been written.
                         */
                        if (handled < 0)
                                goto stall;
                        else if (handled > 0)
                                goto finish;

                        handled = forward_to_driver(musb, &setup);
                        if (handled < 0) {
                                musb_ep_select(mbase, 0);
stall:
                                dev_dbg(musb->controller, "stall (%d)\n", handled);
                                musb->ackpend |= MUSB_CSR0_P_SENDSTALL;
                                musb->ep0_state = MUSB_EP0_STAGE_IDLE;
finish:
                                musb_writew(regs, MUSB_CSR0,
                                                musb->ackpend);
                                musb->ackpend = 0;
                        }
                }
                break;

        case MUSB_EP0_STAGE_ACKWAIT:
                /* This should not happen. But happens with tusb6010 with
                 * g_file_storage and high speed. Do nothing.
                 */
                retval = IRQ_HANDLED;
                break;

        default:
                /* "can't happen" */
                WARN_ON(1);
                musb_writew(regs, MUSB_CSR0, MUSB_CSR0_P_SENDSTALL);
                musb->ep0_state = MUSB_EP0_STAGE_IDLE;
                break;
        }

        return retval;
}


static int
musb_g_ep0_enable(struct usb_ep *ep, const struct usb_endpoint_descriptor *desc)
{
        /* always enabled */
        return -EINVAL;
}

static int musb_g_ep0_disable(struct usb_ep *e)
{
        /* always enabled */
        return -EINVAL;
}

static int
musb_g_ep0_queue(struct usb_ep *e, struct usb_request *r, gfp_t gfp_flags)
{
        struct musb_ep          *ep;
        struct musb_request     *req;
        struct musb             *musb;
        int                     status;
        unsigned long           lockflags;
        void __iomem            *regs;

        if (!e || !r)
                return -EINVAL;

        ep = to_musb_ep(e);
        musb = ep->musb;
        regs = musb->control_ep->regs;

        req = to_musb_request(r);
        req->musb = musb;
        req->request.actual = 0;
        req->request.status = -EINPROGRESS;
        req->tx = ep->is_in;

        spin_lock_irqsave(&musb->lock, lockflags);

        if (!list_empty(&ep->req_list)) {
                status = -EBUSY;
                goto cleanup;
        }

        switch (musb->ep0_state) {
        case MUSB_EP0_STAGE_RX:         /* control-OUT data */
        case MUSB_EP0_STAGE_TX:         /* control-IN data */
        case MUSB_EP0_STAGE_ACKWAIT:    /* zero-length data */
                status = 0;
                break;
        default:
                dev_dbg(musb->controller, "ep0 request queued in state %d\n",
                                musb->ep0_state);
                status = -EINVAL;
                goto cleanup;
        }

        /* add request to the list */
        list_add_tail(&req->list, &ep->req_list);

        dev_dbg(musb->controller, "queue to %s (%s), length=%d\n",
                        ep->name, ep->is_in ? "IN/TX" : "OUT/RX",
                        req->request.length);

        musb_ep_select(musb->mregs, 0);

        /* sequence #1, IN ... start writing the data */
        if (musb->ep0_state == MUSB_EP0_STAGE_TX)
                ep0_txstate(musb);

        /* sequence #3, no-data ... issue IN status */
        else if (musb->ep0_state == MUSB_EP0_STAGE_ACKWAIT) {
                if (req->request.length)
                        status = -EINVAL;
                else {
                        musb->ep0_state = MUSB_EP0_STAGE_STATUSIN;
                        musb_writew(regs, MUSB_CSR0,
                                        musb->ackpend | MUSB_CSR0_P_DATAEND);
                        musb->ackpend = 0;
                        musb_g_ep0_giveback(ep->musb, r);
                }

        /* else for sequence #2 (OUT), caller provides a buffer
         * before the next packet arrives.  deferred responses
         * (after SETUP is acked) are racey.
         */
        } else if (musb->ackpend) {
                musb_writew(regs, MUSB_CSR0, musb->ackpend);

                musb->ackpend = 0;
        }

cleanup:
        spin_unlock_irqrestore(&musb->lock, lockflags);
        return status;
}

static int musb_g_ep0_dequeue(struct usb_ep *ep, struct usb_request *req)
{
        /* we just won't support this */
        return -EINVAL;
}

static int musb_g_ep0_halt(struct usb_ep *e, int value)
{
        struct musb_ep          *ep;
        struct musb             *musb;
        void __iomem            *base, *regs;
        unsigned long           flags;
        int                     status;
        u16                     csr;

        if (!e || !value)
                return -EINVAL;

        ep = to_musb_ep(e);
        musb = ep->musb;
        base = musb->mregs;
        regs = musb->control_ep->regs;
        status = 0;

        spin_lock_irqsave(&musb->lock, flags);

        if (!list_empty(&ep->req_list)) {
                status = -EBUSY;
                goto cleanup;
        }

        musb_ep_select(base, 0);
        csr = musb->ackpend;

        switch (musb->ep0_state) {

        /* Stalls are usually issued after parsing SETUP packet, either
         * directly in irq context from setup() or else later.
         */
        case MUSB_EP0_STAGE_TX:         /* control-IN data */
        case MUSB_EP0_STAGE_ACKWAIT:    /* STALL for zero-length data */
        case MUSB_EP0_STAGE_RX:         /* control-OUT data */
                csr = musb_readw(regs, MUSB_CSR0);
                /* FALLTHROUGH */

        /* It's also OK to issue stalls during callbacks when a non-empty
         * DATA stage buffer has been read (or even written).
         */
        case MUSB_EP0_STAGE_STATUSIN:   /* control-OUT status */
        case MUSB_EP0_STAGE_STATUSOUT:  /* control-IN status */

                csr |= MUSB_CSR0_P_SENDSTALL;
                musb_writew(regs, MUSB_CSR0, csr);
                musb->ep0_state = MUSB_EP0_STAGE_IDLE;
                musb->ackpend = 0;
                break;
        default:
                dev_dbg(musb->controller, "ep0 can't halt in state %d\n", musb->ep0_state);
                status = -EINVAL;
        }

cleanup:
        spin_unlock_irqrestore(&musb->lock, flags);
        return status;
}

const struct usb_ep_ops musb_g_ep0_ops = {
        .enable         = musb_g_ep0_enable,
        .disable        = musb_g_ep0_disable,
        .alloc_request  = musb_alloc_request,
        .free_request   = musb_free_request,
        .queue          = musb_g_ep0_queue,
        .dequeue        = musb_g_ep0_dequeue,
        .set_halt       = musb_g_ep0_halt,
};