// SPDX-License-Identifier: GPL-2.0
/*
 * Driver for the NXP ISP1761 device controller
 *
 * Copyright 2014 Ideas on Board Oy
 *
 * Contacts:
 *      Laurent Pinchart <laurent.pinchart@ideasonboard.com>
 */

#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/timer.h>
#include <linux/usb.h>

#include "isp1760-core.h"
#include "isp1760-regs.h"
#include "isp1760-udc.h"

#define ISP1760_VBUS_POLL_INTERVAL      msecs_to_jiffies(500)

struct isp1760_request {
        struct usb_request req;
        struct list_head queue;
        struct isp1760_ep *ep;
        unsigned int packet_size;
};

static inline struct isp1760_udc *gadget_to_udc(struct usb_gadget *gadget)
{
        return container_of(gadget, struct isp1760_udc, gadget);
}

static inline struct isp1760_ep *ep_to_udc_ep(struct usb_ep *ep)
{
        return container_of(ep, struct isp1760_ep, ep);
}

static inline struct isp1760_request *req_to_udc_req(struct usb_request *req)
{
        return container_of(req, struct isp1760_request, req);
}

static inline u32 isp1760_udc_read(struct isp1760_udc *udc, u16 reg)
{
        return isp1760_read32(udc->regs, reg);
}

static inline void isp1760_udc_write(struct isp1760_udc *udc, u16 reg, u32 val)
{
        isp1760_write32(udc->regs, reg, val);
}

/* -----------------------------------------------------------------------------
 * Endpoint Management
 */

static struct isp1760_ep *isp1760_udc_find_ep(struct isp1760_udc *udc,
                                              u16 index)
{
        unsigned int i;

        if (index == 0)
                return &udc->ep[0];

        for (i = 1; i < ARRAY_SIZE(udc->ep); ++i) {
                if (udc->ep[i].addr == index)
                        return udc->ep[i].desc ? &udc->ep[i] : NULL;
        }

        return NULL;
}

static void __isp1760_udc_select_ep(struct isp1760_ep *ep, int dir)
{
        isp1760_udc_write(ep->udc, DC_EPINDEX,
                          DC_ENDPIDX(ep->addr & USB_ENDPOINT_NUMBER_MASK) |
                          (dir == USB_DIR_IN ? DC_EPDIR : 0));
}

/**
 * isp1760_udc_select_ep - Select an endpoint for register access
 * @ep: The endpoint
 *
 * The ISP1761 endpoint registers are banked. This function selects the target
 * endpoint for banked register access. The selection remains valid until the
 * next call to this function, the next direct access to the EPINDEX register
 * or the next reset, whichever comes first.
 *
 * Called with the UDC spinlock held.
 */
static void isp1760_udc_select_ep(struct isp1760_ep *ep)
{
        __isp1760_udc_select_ep(ep, ep->addr & USB_ENDPOINT_DIR_MASK);
}

/* Called with the UDC spinlock held. */
static void isp1760_udc_ctrl_send_status(struct isp1760_ep *ep, int dir)
{
        struct isp1760_udc *udc = ep->udc;

        /*
         * Proceed to the status stage. The status stage data packet flows in
         * the direction opposite to the data stage data packets, we thus need
         * to select the OUT/IN endpoint for IN/OUT transfers.
         */
        isp1760_udc_write(udc, DC_EPINDEX, DC_ENDPIDX(0) |
                          (dir == USB_DIR_IN ? 0 : DC_EPDIR));
        isp1760_udc_write(udc, DC_CTRLFUNC, DC_STATUS);

        /*
         * The hardware will terminate the request automatically and go back to
         * the setup stage without notifying us.
         */
        udc->ep0_state = ISP1760_CTRL_SETUP;
}

/* Called without the UDC spinlock held. */
static void isp1760_udc_request_complete(struct isp1760_ep *ep,
                                         struct isp1760_request *req,
                                         int status)
{
        struct isp1760_udc *udc = ep->udc;
        unsigned long flags;

        dev_dbg(ep->udc->isp->dev, "completing request %p with status %d\n",
                req, status);

        req->ep = NULL;
        req->req.status = status;
        req->req.complete(&ep->ep, &req->req);

        spin_lock_irqsave(&udc->lock, flags);

        /*
         * When completing control OUT requests, move to the status stage after
         * calling the request complete callback. This gives the gadget an
         * opportunity to stall the control transfer if needed.
         */
        if (status == 0 && ep->addr == 0 && udc->ep0_dir == USB_DIR_OUT)
                isp1760_udc_ctrl_send_status(ep, USB_DIR_OUT);

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

static void isp1760_udc_ctrl_send_stall(struct isp1760_ep *ep)
{
        struct isp1760_udc *udc = ep->udc;
        unsigned long flags;

        dev_dbg(ep->udc->isp->dev, "%s(ep%02x)\n", __func__, ep->addr);

        spin_lock_irqsave(&udc->lock, flags);

        /* Stall both the IN and OUT endpoints. */
        __isp1760_udc_select_ep(ep, USB_DIR_OUT);
        isp1760_udc_write(udc, DC_CTRLFUNC, DC_STALL);
        __isp1760_udc_select_ep(ep, USB_DIR_IN);
        isp1760_udc_write(udc, DC_CTRLFUNC, DC_STALL);

        /* A protocol stall completes the control transaction. */
        udc->ep0_state = ISP1760_CTRL_SETUP;

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

/* -----------------------------------------------------------------------------
 * Data Endpoints
 */

/* Called with the UDC spinlock held. */
static bool isp1760_udc_receive(struct isp1760_ep *ep,
                                struct isp1760_request *req)
{
        struct isp1760_udc *udc = ep->udc;
        unsigned int len;
        u32 *buf;
        int i;

        isp1760_udc_select_ep(ep);
        len = isp1760_udc_read(udc, DC_BUFLEN) & DC_DATACOUNT_MASK;

        dev_dbg(udc->isp->dev, "%s: received %u bytes (%u/%u done)\n",
                __func__, len, req->req.actual, req->req.length);

        len = min(len, req->req.length - req->req.actual);

        if (!len) {
                /*
                 * There's no data to be read from the FIFO, acknowledge the RX
                 * interrupt by clearing the buffer.
                 *
                 * TODO: What if another packet arrives in the meantime ? The
                 * datasheet doesn't clearly document how this should be
                 * handled.
                 */
                isp1760_udc_write(udc, DC_CTRLFUNC, DC_CLBUF);
                return false;
        }

        buf = req->req.buf + req->req.actual;

        /*
         * Make sure not to read more than one extra byte, otherwise data from
         * the next packet might be removed from the FIFO.
         */
        for (i = len; i > 2; i -= 4, ++buf)
                *buf = le32_to_cpu(isp1760_udc_read(udc, DC_DATAPORT));
        if (i > 0)
                *(u16 *)buf = le16_to_cpu(readw(udc->regs + DC_DATAPORT));

        req->req.actual += len;

        /*
         * TODO: The short_not_ok flag isn't supported yet, but isn't used by
         * any gadget driver either.
         */

        dev_dbg(udc->isp->dev,
                "%s: req %p actual/length %u/%u maxpacket %u packet size %u\n",
                __func__, req, req->req.actual, req->req.length, ep->maxpacket,
                len);

        ep->rx_pending = false;

        /*
         * Complete the request if all data has been received or if a short
         * packet has been received.
         */
        if (req->req.actual == req->req.length || len < ep->maxpacket) {
                list_del(&req->queue);
                return true;
        }

        return false;
}

static void isp1760_udc_transmit(struct isp1760_ep *ep,
                                 struct isp1760_request *req)
{
        struct isp1760_udc *udc = ep->udc;
        u32 *buf = req->req.buf + req->req.actual;
        int i;

        req->packet_size = min(req->req.length - req->req.actual,
                               ep->maxpacket);

        dev_dbg(udc->isp->dev, "%s: transferring %u bytes (%u/%u done)\n",
                __func__, req->packet_size, req->req.actual,
                req->req.length);

        __isp1760_udc_select_ep(ep, USB_DIR_IN);

        if (req->packet_size)
                isp1760_udc_write(udc, DC_BUFLEN, req->packet_size);

        /*
         * Make sure not to write more than one extra byte, otherwise extra data
         * will stay in the FIFO and will be transmitted during the next control
         * request. The endpoint control CLBUF bit is supposed to allow flushing
         * the FIFO for this kind of conditions, but doesn't seem to work.
         */
        for (i = req->packet_size; i > 2; i -= 4, ++buf)
                isp1760_udc_write(udc, DC_DATAPORT, cpu_to_le32(*buf));
        if (i > 0)
                writew(cpu_to_le16(*(u16 *)buf), udc->regs + DC_DATAPORT);

        if (ep->addr == 0)
                isp1760_udc_write(udc, DC_CTRLFUNC, DC_DSEN);
        if (!req->packet_size)
                isp1760_udc_write(udc, DC_CTRLFUNC, DC_VENDP);
}

static void isp1760_ep_rx_ready(struct isp1760_ep *ep)
{
        struct isp1760_udc *udc = ep->udc;
        struct isp1760_request *req;
        bool complete;

        spin_lock(&udc->lock);

        if (ep->addr == 0 && udc->ep0_state != ISP1760_CTRL_DATA_OUT) {
                spin_unlock(&udc->lock);
                dev_dbg(udc->isp->dev, "%s: invalid ep0 state %u\n", __func__,
                        udc->ep0_state);
                return;
        }

        if (ep->addr != 0 && !ep->desc) {
                spin_unlock(&udc->lock);
                dev_dbg(udc->isp->dev, "%s: ep%02x is disabled\n", __func__,
                        ep->addr);
                return;
        }

        if (list_empty(&ep->queue)) {
                ep->rx_pending = true;
                spin_unlock(&udc->lock);
                dev_dbg(udc->isp->dev, "%s: ep%02x (%p) has no request queued\n",
                        __func__, ep->addr, ep);
                return;
        }

        req = list_first_entry(&ep->queue, struct isp1760_request,
                               queue);
        complete = isp1760_udc_receive(ep, req);

        spin_unlock(&udc->lock);

        if (complete)
                isp1760_udc_request_complete(ep, req, 0);
}

static void isp1760_ep_tx_complete(struct isp1760_ep *ep)
{
        struct isp1760_udc *udc = ep->udc;
        struct isp1760_request *complete = NULL;
        struct isp1760_request *req;
        bool need_zlp;

        spin_lock(&udc->lock);

        if (ep->addr == 0 && udc->ep0_state != ISP1760_CTRL_DATA_IN) {
                spin_unlock(&udc->lock);
                dev_dbg(udc->isp->dev, "TX IRQ: invalid endpoint state %u\n",
                        udc->ep0_state);
                return;
        }

        if (list_empty(&ep->queue)) {
                /*
                 * This can happen for the control endpoint when the reply to
                 * the GET_STATUS IN control request is sent directly by the
                 * setup IRQ handler. Just proceed to the status stage.
                 */
                if (ep->addr == 0) {
                        isp1760_udc_ctrl_send_status(ep, USB_DIR_IN);
                        spin_unlock(&udc->lock);
                        return;
                }

                spin_unlock(&udc->lock);
                dev_dbg(udc->isp->dev, "%s: ep%02x has no request queued\n",
                        __func__, ep->addr);
                return;
        }

        req = list_first_entry(&ep->queue, struct isp1760_request,
                               queue);
        req->req.actual += req->packet_size;

        need_zlp = req->req.actual == req->req.length &&
                   !(req->req.length % ep->maxpacket) &&
                   req->packet_size && req->req.zero;

        dev_dbg(udc->isp->dev,
                "TX IRQ: req %p actual/length %u/%u maxpacket %u packet size %u zero %u need zlp %u\n",
                 req, req->req.actual, req->req.length, ep->maxpacket,
                 req->packet_size, req->req.zero, need_zlp);

        /*
         * Complete the request if all data has been sent and we don't need to
         * transmit a zero length packet.
         */
        if (req->req.actual == req->req.length && !need_zlp) {
                complete = req;
                list_del(&req->queue);

                if (ep->addr == 0)
                        isp1760_udc_ctrl_send_status(ep, USB_DIR_IN);

                if (!list_empty(&ep->queue))
                        req = list_first_entry(&ep->queue,
                                               struct isp1760_request, queue);
                else
                        req = NULL;
        }

        /*
         * Transmit the next packet or start the next request, if any.
         *
         * TODO: If the endpoint is stalled the next request shouldn't be
         * started, but what about the next packet ?
         */
        if (req)
                isp1760_udc_transmit(ep, req);

        spin_unlock(&udc->lock);

        if (complete)
                isp1760_udc_request_complete(ep, complete, 0);
}

static int __isp1760_udc_set_halt(struct isp1760_ep *ep, bool halt)
{
        struct isp1760_udc *udc = ep->udc;

        dev_dbg(udc->isp->dev, "%s: %s halt on ep%02x\n", __func__,
                halt ? "set" : "clear", ep->addr);

        if (ep->desc && usb_endpoint_xfer_isoc(ep->desc)) {
                dev_dbg(udc->isp->dev, "%s: ep%02x is isochronous\n", __func__,
                        ep->addr);
                return -EINVAL;
        }

        isp1760_udc_select_ep(ep);
        isp1760_udc_write(udc, DC_CTRLFUNC, halt ? DC_STALL : 0);

        if (ep->addr == 0) {
                /* When halting the control endpoint, stall both IN and OUT. */
                __isp1760_udc_select_ep(ep, USB_DIR_IN);
                isp1760_udc_write(udc, DC_CTRLFUNC, halt ? DC_STALL : 0);
        } else if (!halt) {
                /* Reset the data PID by cycling the endpoint enable bit. */
                u16 eptype = isp1760_udc_read(udc, DC_EPTYPE);

                isp1760_udc_write(udc, DC_EPTYPE, eptype & ~DC_EPENABLE);
                isp1760_udc_write(udc, DC_EPTYPE, eptype);

                /*
                 * Disabling the endpoint emptied the transmit FIFO, fill it
                 * again if a request is pending.
                 *
                 * TODO: Does the gadget framework require synchronizatino with
                 * the TX IRQ handler ?
                 */
                if ((ep->addr & USB_DIR_IN) && !list_empty(&ep->queue)) {
                        struct isp1760_request *req;

                        req = list_first_entry(&ep->queue,
                                               struct isp1760_request, queue);
                        isp1760_udc_transmit(ep, req);
                }
        }

        ep->halted = halt;

        return 0;
}

/* -----------------------------------------------------------------------------
 * Control Endpoint
 */

static int isp1760_udc_get_status(struct isp1760_udc *udc,
                                  const struct usb_ctrlrequest *req)
{
        struct isp1760_ep *ep;
        u16 status;

        if (req->wLength != cpu_to_le16(2) || req->wValue != cpu_to_le16(0))
                return -EINVAL;

        switch (req->bRequestType) {
        case USB_DIR_IN | USB_RECIP_DEVICE:
                status = udc->devstatus;
                break;

        case USB_DIR_IN | USB_RECIP_INTERFACE:
                status = 0;
                break;

        case USB_DIR_IN | USB_RECIP_ENDPOINT:
                ep = isp1760_udc_find_ep(udc, le16_to_cpu(req->wIndex));
                if (!ep)
                        return -EINVAL;

                status = 0;
                if (ep->halted)
                        status |= 1 << USB_ENDPOINT_HALT;
                break;

        default:
                return -EINVAL;
        }

        isp1760_udc_write(udc, DC_EPINDEX, DC_ENDPIDX(0) | DC_EPDIR);
        isp1760_udc_write(udc, DC_BUFLEN, 2);

        writew(cpu_to_le16(status), udc->regs + DC_DATAPORT);

        isp1760_udc_write(udc, DC_CTRLFUNC, DC_DSEN);

        dev_dbg(udc->isp->dev, "%s: status 0x%04x\n", __func__, status);

        return 0;
}

static int isp1760_udc_set_address(struct isp1760_udc *udc, u16 addr)
{
        if (addr > 127) {
                dev_dbg(udc->isp->dev, "invalid device address %u\n", addr);
                return -EINVAL;
        }

        if (udc->gadget.state != USB_STATE_DEFAULT &&
            udc->gadget.state != USB_STATE_ADDRESS) {
                dev_dbg(udc->isp->dev, "can't set address in state %u\n",
                        udc->gadget.state);
                return -EINVAL;
        }

        usb_gadget_set_state(&udc->gadget, addr ? USB_STATE_ADDRESS :
                             USB_STATE_DEFAULT);

        isp1760_udc_write(udc, DC_ADDRESS, DC_DEVEN | addr);

        spin_lock(&udc->lock);
        isp1760_udc_ctrl_send_status(&udc->ep[0], USB_DIR_OUT);
        spin_unlock(&udc->lock);

        return 0;
}

static bool isp1760_ep0_setup_standard(struct isp1760_udc *udc,
                                       struct usb_ctrlrequest *req)
{
        bool stall;

        switch (req->bRequest) {
        case USB_REQ_GET_STATUS:
                return isp1760_udc_get_status(udc, req);

        case USB_REQ_CLEAR_FEATURE:
                switch (req->bRequestType) {
                case USB_DIR_OUT | USB_RECIP_DEVICE: {
                        /* TODO: Handle remote wakeup feature. */
                        return true;
                }

                case USB_DIR_OUT | USB_RECIP_ENDPOINT: {
                        u16 index = le16_to_cpu(req->wIndex);
                        struct isp1760_ep *ep;

                        if (req->wLength != cpu_to_le16(0) ||
                            req->wValue != cpu_to_le16(USB_ENDPOINT_HALT))
                                return true;

                        ep = isp1760_udc_find_ep(udc, index);
                        if (!ep)
                                return true;

                        spin_lock(&udc->lock);

                        /*
                         * If the endpoint is wedged only the gadget can clear
                         * the halt feature. Pretend success in that case, but
                         * keep the endpoint halted.
                         */
                        if (!ep->wedged)
                                stall = __isp1760_udc_set_halt(ep, false);
                        else
                                stall = false;

                        if (!stall)
                                isp1760_udc_ctrl_send_status(&udc->ep[0],
                                                             USB_DIR_OUT);

                        spin_unlock(&udc->lock);
                        return stall;
                }

                default:
                        return true;
                }
                break;

        case USB_REQ_SET_FEATURE:
                switch (req->bRequestType) {
                case USB_DIR_OUT | USB_RECIP_DEVICE: {
                        /* TODO: Handle remote wakeup and test mode features */
                        return true;
                }

                case USB_DIR_OUT | USB_RECIP_ENDPOINT: {
                        u16 index = le16_to_cpu(req->wIndex);
                        struct isp1760_ep *ep;

                        if (req->wLength != cpu_to_le16(0) ||
                            req->wValue != cpu_to_le16(USB_ENDPOINT_HALT))
                                return true;

                        ep = isp1760_udc_find_ep(udc, index);
                        if (!ep)
                                return true;

                        spin_lock(&udc->lock);

                        stall = __isp1760_udc_set_halt(ep, true);
                        if (!stall)
                                isp1760_udc_ctrl_send_status(&udc->ep[0],
                                                             USB_DIR_OUT);

                        spin_unlock(&udc->lock);
                        return stall;
                }

                default:
                        return true;
                }
                break;

        case USB_REQ_SET_ADDRESS:
                if (req->bRequestType != (USB_DIR_OUT | USB_RECIP_DEVICE))
                        return true;

                return isp1760_udc_set_address(udc, le16_to_cpu(req->wValue));

        case USB_REQ_SET_CONFIGURATION:
                if (req->bRequestType != (USB_DIR_OUT | USB_RECIP_DEVICE))
                        return true;

                if (udc->gadget.state != USB_STATE_ADDRESS &&
                    udc->gadget.state != USB_STATE_CONFIGURED)
                        return true;

                stall = udc->driver->setup(&udc->gadget, req) < 0;
                if (stall)
                        return true;

                usb_gadget_set_state(&udc->gadget, req->wValue ?
                                     USB_STATE_CONFIGURED : USB_STATE_ADDRESS);

                /*
                 * SET_CONFIGURATION (and SET_INTERFACE) must reset the halt
                 * feature on all endpoints. There is however no need to do so
                 * explicitly here as the gadget driver will disable and
                 * reenable endpoints, clearing the halt feature.
                 */
                return false;

        default:
                return udc->driver->setup(&udc->gadget, req) < 0;
        }
}

static void isp1760_ep0_setup(struct isp1760_udc *udc)
{
        union {
                struct usb_ctrlrequest r;
                u32 data[2];
        } req;
        unsigned int count;
        bool stall = false;

        spin_lock(&udc->lock);

        isp1760_udc_write(udc, DC_EPINDEX, DC_EP0SETUP);

        count = isp1760_udc_read(udc, DC_BUFLEN) & DC_DATACOUNT_MASK;
        if (count != sizeof(req)) {
                spin_unlock(&udc->lock);

                dev_err(udc->isp->dev, "invalid length %u for setup packet\n",
                        count);

                isp1760_udc_ctrl_send_stall(&udc->ep[0]);
                return;
        }

        req.data[0] = isp1760_udc_read(udc, DC_DATAPORT);
        req.data[1] = isp1760_udc_read(udc, DC_DATAPORT);

        if (udc->ep0_state != ISP1760_CTRL_SETUP) {
                spin_unlock(&udc->lock);
                dev_dbg(udc->isp->dev, "unexpected SETUP packet\n");
                return;
        }

        /* Move to the data stage. */
        if (!req.r.wLength)
                udc->ep0_state = ISP1760_CTRL_STATUS;
        else if (req.r.bRequestType & USB_DIR_IN)
                udc->ep0_state = ISP1760_CTRL_DATA_IN;
        else
                udc->ep0_state = ISP1760_CTRL_DATA_OUT;

        udc->ep0_dir = req.r.bRequestType & USB_DIR_IN;
        udc->ep0_length = le16_to_cpu(req.r.wLength);

        spin_unlock(&udc->lock);

        dev_dbg(udc->isp->dev,
                "%s: bRequestType 0x%02x bRequest 0x%02x wValue 0x%04x wIndex 0x%04x wLength 0x%04x\n",
                __func__, req.r.bRequestType, req.r.bRequest,
                le16_to_cpu(req.r.wValue), le16_to_cpu(req.r.wIndex),
                le16_to_cpu(req.r.wLength));

        if ((req.r.bRequestType & USB_TYPE_MASK) == USB_TYPE_STANDARD)
                stall = isp1760_ep0_setup_standard(udc, &req.r);
        else
                stall = udc->driver->setup(&udc->gadget, &req.r) < 0;

        if (stall)
                isp1760_udc_ctrl_send_stall(&udc->ep[0]);
}

/* -----------------------------------------------------------------------------
 * Gadget Endpoint Operations
 */

static int isp1760_ep_enable(struct usb_ep *ep,
                             const struct usb_endpoint_descriptor *desc)
{
        struct isp1760_ep *uep = ep_to_udc_ep(ep);
        struct isp1760_udc *udc = uep->udc;
        unsigned long flags;
        unsigned int type;

        dev_dbg(uep->udc->isp->dev, "%s\n", __func__);

        /*
         * Validate the descriptor. The control endpoint can't be enabled
         * manually.
         */
        if (desc->bDescriptorType != USB_DT_ENDPOINT ||
            desc->bEndpointAddress == 0 ||
            desc->bEndpointAddress != uep->addr ||
            le16_to_cpu(desc->wMaxPacketSize) > ep->maxpacket) {
                dev_dbg(udc->isp->dev,
                        "%s: invalid descriptor type %u addr %02x ep addr %02x max packet size %u/%u\n",
                        __func__, desc->bDescriptorType,
                        desc->bEndpointAddress, uep->addr,
                        le16_to_cpu(desc->wMaxPacketSize), ep->maxpacket);
                return -EINVAL;
        }

        switch (usb_endpoint_type(desc)) {
        case USB_ENDPOINT_XFER_ISOC:
                type = DC_ENDPTYP_ISOC;
                break;
        case USB_ENDPOINT_XFER_BULK:
                type = DC_ENDPTYP_BULK;
                break;
        case USB_ENDPOINT_XFER_INT:
                type = DC_ENDPTYP_INTERRUPT;
                break;
        case USB_ENDPOINT_XFER_CONTROL:
        default:
                dev_dbg(udc->isp->dev, "%s: control endpoints unsupported\n",
                        __func__);
                return -EINVAL;
        }

        spin_lock_irqsave(&udc->lock, flags);

        uep->desc = desc;
        uep->maxpacket = le16_to_cpu(desc->wMaxPacketSize);
        uep->rx_pending = false;
        uep->halted = false;
        uep->wedged = false;

        isp1760_udc_select_ep(uep);
        isp1760_udc_write(udc, DC_EPMAXPKTSZ, uep->maxpacket);
        isp1760_udc_write(udc, DC_BUFLEN, uep->maxpacket);
        isp1760_udc_write(udc, DC_EPTYPE, DC_EPENABLE | type);

        spin_unlock_irqrestore(&udc->lock, flags);

        return 0;
}

static int isp1760_ep_disable(struct usb_ep *ep)
{
        struct isp1760_ep *uep = ep_to_udc_ep(ep);
        struct isp1760_udc *udc = uep->udc;
        struct isp1760_request *req, *nreq;
        LIST_HEAD(req_list);
        unsigned long flags;

        dev_dbg(udc->isp->dev, "%s\n", __func__);

        spin_lock_irqsave(&udc->lock, flags);

        if (!uep->desc) {
                dev_dbg(udc->isp->dev, "%s: endpoint not enabled\n", __func__);
                spin_unlock_irqrestore(&udc->lock, flags);
                return -EINVAL;
        }

        uep->desc = NULL;
        uep->maxpacket = 0;

        isp1760_udc_select_ep(uep);
        isp1760_udc_write(udc, DC_EPTYPE, 0);

        /* TODO Synchronize with the IRQ handler */

        list_splice_init(&uep->queue, &req_list);

        spin_unlock_irqrestore(&udc->lock, flags);

        list_for_each_entry_safe(req, nreq, &req_list, queue) {
                list_del(&req->queue);
                isp1760_udc_request_complete(uep, req, -ESHUTDOWN);
        }

        return 0;
}

static struct usb_request *isp1760_ep_alloc_request(struct usb_ep *ep,
                                                    gfp_t gfp_flags)
{
        struct isp1760_request *req;

        req = kzalloc(sizeof(*req), gfp_flags);
        if (!req)
                return NULL;

        return &req->req;
}

static void isp1760_ep_free_request(struct usb_ep *ep, struct usb_request *_req)
{
        struct isp1760_request *req = req_to_udc_req(_req);

        kfree(req);
}

static int isp1760_ep_queue(struct usb_ep *ep, struct usb_request *_req,
                            gfp_t gfp_flags)
{
        struct isp1760_request *req = req_to_udc_req(_req);
        struct isp1760_ep *uep = ep_to_udc_ep(ep);
        struct isp1760_udc *udc = uep->udc;
        bool complete = false;
        unsigned long flags;
        int ret = 0;

        _req->status = -EINPROGRESS;
        _req->actual = 0;

        spin_lock_irqsave(&udc->lock, flags);

        dev_dbg(udc->isp->dev,
                "%s: req %p (%u bytes%s) ep %p(0x%02x)\n", __func__, _req,
                _req->length, _req->zero ? " (zlp)" : "", uep, uep->addr);

        req->ep = uep;

        if (uep->addr == 0) {
                if (_req->length != udc->ep0_length &&
                    udc->ep0_state != ISP1760_CTRL_DATA_IN) {
                        dev_dbg(udc->isp->dev,
                                "%s: invalid length %u for req %p\n",
                                __func__, _req->length, req);
                        ret = -EINVAL;
                        goto done;
                }

                switch (udc->ep0_state) {
                case ISP1760_CTRL_DATA_IN:
                        dev_dbg(udc->isp->dev, "%s: transmitting req %p\n",
                                __func__, req);

                        list_add_tail(&req->queue, &uep->queue);
                        isp1760_udc_transmit(uep, req);
                        break;

                case ISP1760_CTRL_DATA_OUT:
                        list_add_tail(&req->queue, &uep->queue);
                        __isp1760_udc_select_ep(uep, USB_DIR_OUT);
                        isp1760_udc_write(udc, DC_CTRLFUNC, DC_DSEN);
                        break;

                case ISP1760_CTRL_STATUS:
                        complete = true;
                        break;

                default:
                        dev_dbg(udc->isp->dev, "%s: invalid ep0 state\n",
                                __func__);
                        ret = -EINVAL;
                        break;
                }
        } else if (uep->desc) {
                bool empty = list_empty(&uep->queue);

                list_add_tail(&req->queue, &uep->queue);
                if ((uep->addr & USB_DIR_IN) && !uep->halted && empty)
                        isp1760_udc_transmit(uep, req);
                else if (!(uep->addr & USB_DIR_IN) && uep->rx_pending)
                        complete = isp1760_udc_receive(uep, req);
        } else {
                dev_dbg(udc->isp->dev,
                        "%s: can't queue request to disabled ep%02x\n",
                        __func__, uep->addr);
                ret = -ESHUTDOWN;
        }

done:
        if (ret < 0)
                req->ep = NULL;

        spin_unlock_irqrestore(&udc->lock, flags);

        if (complete)
                isp1760_udc_request_complete(uep, req, 0);

        return ret;
}

static int isp1760_ep_dequeue(struct usb_ep *ep, struct usb_request *_req)
{
        struct isp1760_request *req = req_to_udc_req(_req);
        struct isp1760_ep *uep = ep_to_udc_ep(ep);
        struct isp1760_udc *udc = uep->udc;
        unsigned long flags;

        dev_dbg(uep->udc->isp->dev, "%s(ep%02x)\n", __func__, uep->addr);

        spin_lock_irqsave(&udc->lock, flags);

        if (req->ep != uep)
                req = NULL;
        else
                list_del(&req->queue);

        spin_unlock_irqrestore(&udc->lock, flags);

        if (!req)
                return -EINVAL;

        isp1760_udc_request_complete(uep, req, -ECONNRESET);
        return 0;
}

static int __isp1760_ep_set_halt(struct isp1760_ep *uep, bool stall, bool wedge)
{
        struct isp1760_udc *udc = uep->udc;
        int ret;

        if (!uep->addr) {
                /*
                 * Halting the control endpoint is only valid as a delayed error
                 * response to a SETUP packet. Make sure EP0 is in the right
                 * stage and that the gadget isn't trying to clear the halt
                 * condition.
                 */
                if (WARN_ON(udc->ep0_state == ISP1760_CTRL_SETUP || !stall ||
                             wedge)) {
                        return -EINVAL;
                }
        }

        if (uep->addr && !uep->desc) {
                dev_dbg(udc->isp->dev, "%s: ep%02x is disabled\n", __func__,
                        uep->addr);
                return -EINVAL;
        }

        if (uep->addr & USB_DIR_IN) {
                /* Refuse to halt IN endpoints with active transfers. */
                if (!list_empty(&uep->queue)) {
                        dev_dbg(udc->isp->dev,
                                "%s: ep%02x has request pending\n", __func__,
                                uep->addr);
                        return -EAGAIN;
                }
        }

        ret = __isp1760_udc_set_halt(uep, stall);
        if (ret < 0)
                return ret;

        if (!uep->addr) {
                /*
                 * Stalling EP0 completes the control transaction, move back to
                 * the SETUP state.
                 */
                udc->ep0_state = ISP1760_CTRL_SETUP;
                return 0;
        }

        if (wedge)
                uep->wedged = true;
        else if (!stall)
                uep->wedged = false;

        return 0;
}

static int isp1760_ep_set_halt(struct usb_ep *ep, int value)
{
        struct isp1760_ep *uep = ep_to_udc_ep(ep);
        unsigned long flags;
        int ret;

        dev_dbg(uep->udc->isp->dev, "%s: %s halt on ep%02x\n", __func__,
                value ? "set" : "clear", uep->addr);

        spin_lock_irqsave(&uep->udc->lock, flags);
        ret = __isp1760_ep_set_halt(uep, value, false);
        spin_unlock_irqrestore(&uep->udc->lock, flags);

        return ret;
}

static int isp1760_ep_set_wedge(struct usb_ep *ep)
{
        struct isp1760_ep *uep = ep_to_udc_ep(ep);
        unsigned long flags;
        int ret;

        dev_dbg(uep->udc->isp->dev, "%s: set wedge on ep%02x)\n", __func__,
                uep->addr);

        spin_lock_irqsave(&uep->udc->lock, flags);
        ret = __isp1760_ep_set_halt(uep, true, true);
        spin_unlock_irqrestore(&uep->udc->lock, flags);

        return ret;
}

static void isp1760_ep_fifo_flush(struct usb_ep *ep)
{
        struct isp1760_ep *uep = ep_to_udc_ep(ep);
        struct isp1760_udc *udc = uep->udc;
        unsigned long flags;

        spin_lock_irqsave(&udc->lock, flags);

        isp1760_udc_select_ep(uep);

        /*
         * Set the CLBUF bit twice to flush both buffers in case double
         * buffering is enabled.
         */
        isp1760_udc_write(udc, DC_CTRLFUNC, DC_CLBUF);
        isp1760_udc_write(udc, DC_CTRLFUNC, DC_CLBUF);

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

static const struct usb_ep_ops isp1760_ep_ops = {
        .enable = isp1760_ep_enable,
        .disable = isp1760_ep_disable,
        .alloc_request = isp1760_ep_alloc_request,
        .free_request = isp1760_ep_free_request,
        .queue = isp1760_ep_queue,
        .dequeue = isp1760_ep_dequeue,
        .set_halt = isp1760_ep_set_halt,
        .set_wedge = isp1760_ep_set_wedge,
        .fifo_flush = isp1760_ep_fifo_flush,
};

/* -----------------------------------------------------------------------------
 * Device States
 */

/* Called with the UDC spinlock held. */
static void isp1760_udc_connect(struct isp1760_udc *udc)
{
        usb_gadget_set_state(&udc->gadget, USB_STATE_POWERED);
        mod_timer(&udc->vbus_timer, jiffies + ISP1760_VBUS_POLL_INTERVAL);
}

/* Called with the UDC spinlock held. */
static void isp1760_udc_disconnect(struct isp1760_udc *udc)
{
        if (udc->gadget.state < USB_STATE_POWERED)
                return;

        dev_dbg(udc->isp->dev, "Device disconnected in state %u\n",
                 udc->gadget.state);

        udc->gadget.speed = USB_SPEED_UNKNOWN;
        usb_gadget_set_state(&udc->gadget, USB_STATE_ATTACHED);

        if (udc->driver->disconnect)
                udc->driver->disconnect(&udc->gadget);

        del_timer(&udc->vbus_timer);

        /* TODO Reset all endpoints ? */
}

static void isp1760_udc_init_hw(struct isp1760_udc *udc)
{
        /*
         * The device controller currently shares its interrupt with the host
         * controller, the DC_IRQ polarity and signaling mode are ignored. Set
         * the to active-low level-triggered.
         *
         * Configure the control, in and out pipes to generate interrupts on
         * ACK tokens only (and NYET for the out pipe). The default
         * configuration also generates an interrupt on the first NACK token.
         */
        isp1760_udc_write(udc, DC_INTCONF, DC_CDBGMOD_ACK | DC_DDBGMODIN_ACK |
                          DC_DDBGMODOUT_ACK_NYET);

        isp1760_udc_write(udc, DC_INTENABLE, DC_IEPRXTX(7) | DC_IEPRXTX(6) |
                          DC_IEPRXTX(5) | DC_IEPRXTX(4) | DC_IEPRXTX(3) |
                          DC_IEPRXTX(2) | DC_IEPRXTX(1) | DC_IEPRXTX(0) |
                          DC_IEP0SETUP | DC_IEVBUS | DC_IERESM | DC_IESUSP |
                          DC_IEHS_STA | DC_IEBRST);

        if (udc->connected)
                isp1760_set_pullup(udc->isp, true);

        isp1760_udc_write(udc, DC_ADDRESS, DC_DEVEN);
}

static void isp1760_udc_reset(struct isp1760_udc *udc)
{
        unsigned long flags;

        spin_lock_irqsave(&udc->lock, flags);

        /*
         * The bus reset has reset most registers to their default value,
         * reinitialize the UDC hardware.
         */
        isp1760_udc_init_hw(udc);

        udc->ep0_state = ISP1760_CTRL_SETUP;
        udc->gadget.speed = USB_SPEED_FULL;

        usb_gadget_udc_reset(&udc->gadget, udc->driver);

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

static void isp1760_udc_suspend(struct isp1760_udc *udc)
{
        if (udc->gadget.state < USB_STATE_DEFAULT)
                return;

        if (udc->driver->suspend)
                udc->driver->suspend(&udc->gadget);
}

static void isp1760_udc_resume(struct isp1760_udc *udc)
{
        if (udc->gadget.state < USB_STATE_DEFAULT)
                return;

        if (udc->driver->resume)
                udc->driver->resume(&udc->gadget);
}

/* -----------------------------------------------------------------------------
 * Gadget Operations
 */

static int isp1760_udc_get_frame(struct usb_gadget *gadget)
{
        struct isp1760_udc *udc = gadget_to_udc(gadget);

        return isp1760_udc_read(udc, DC_FRAMENUM) & ((1 << 11) - 1);
}

static int isp1760_udc_wakeup(struct usb_gadget *gadget)
{
        struct isp1760_udc *udc = gadget_to_udc(gadget);

        dev_dbg(udc->isp->dev, "%s\n", __func__);
        return -ENOTSUPP;
}

static int isp1760_udc_set_selfpowered(struct usb_gadget *gadget,
                                       int is_selfpowered)
{
        struct isp1760_udc *udc = gadget_to_udc(gadget);

        if (is_selfpowered)
                udc->devstatus |= 1 << USB_DEVICE_SELF_POWERED;
        else
                udc->devstatus &= ~(1 << USB_DEVICE_SELF_POWERED);

        return 0;
}

static int isp1760_udc_pullup(struct usb_gadget *gadget, int is_on)
{
        struct isp1760_udc *udc = gadget_to_udc(gadget);

        isp1760_set_pullup(udc->isp, is_on);
        udc->connected = is_on;

        return 0;
}

static int isp1760_udc_start(struct usb_gadget *gadget,
                             struct usb_gadget_driver *driver)
{
        struct isp1760_udc *udc = gadget_to_udc(gadget);
        unsigned long flags;

        /* The hardware doesn't support low speed. */
        if (driver->max_speed < USB_SPEED_FULL) {
                dev_err(udc->isp->dev, "Invalid gadget driver\n");
                return -EINVAL;
        }

        spin_lock_irqsave(&udc->lock, flags);

        if (udc->driver) {
                dev_err(udc->isp->dev, "UDC already has a gadget driver\n");
                spin_unlock_irqrestore(&udc->lock, flags);
                return -EBUSY;
        }

        udc->driver = driver;

        spin_unlock_irqrestore(&udc->lock, flags);

        dev_dbg(udc->isp->dev, "starting UDC with driver %s\n",
                driver->function);

        udc->devstatus = 0;
        udc->connected = true;

        usb_gadget_set_state(&udc->gadget, USB_STATE_ATTACHED);

        /* DMA isn't supported yet, don't enable the DMA clock. */
        isp1760_udc_write(udc, DC_MODE, DC_GLINTENA);

        isp1760_udc_init_hw(udc);

        dev_dbg(udc->isp->dev, "UDC started with driver %s\n",
                driver->function);

        return 0;
}

static int isp1760_udc_stop(struct usb_gadget *gadget)
{
        struct isp1760_udc *udc = gadget_to_udc(gadget);
        unsigned long flags;

        dev_dbg(udc->isp->dev, "%s\n", __func__);

        del_timer_sync(&udc->vbus_timer);

        isp1760_udc_write(udc, DC_MODE, 0);

        spin_lock_irqsave(&udc->lock, flags);
        udc->driver = NULL;
        spin_unlock_irqrestore(&udc->lock, flags);

        return 0;
}

static const struct usb_gadget_ops isp1760_udc_ops = {
        .get_frame = isp1760_udc_get_frame,
        .wakeup = isp1760_udc_wakeup,
        .set_selfpowered = isp1760_udc_set_selfpowered,
        .pullup = isp1760_udc_pullup,
        .udc_start = isp1760_udc_start,
        .udc_stop = isp1760_udc_stop,
};

/* -----------------------------------------------------------------------------
 * Interrupt Handling
 */

static irqreturn_t isp1760_udc_irq(int irq, void *dev)
{
        struct isp1760_udc *udc = dev;
        unsigned int i;
        u32 status;

        status = isp1760_udc_read(udc, DC_INTERRUPT)
               & isp1760_udc_read(udc, DC_INTENABLE);
        isp1760_udc_write(udc, DC_INTERRUPT, status);

        if (status & DC_IEVBUS) {
                dev_dbg(udc->isp->dev, "%s(VBUS)\n", __func__);
                /* The VBUS interrupt is only triggered when VBUS appears. */
                spin_lock(&udc->lock);
                isp1760_udc_connect(udc);
                spin_unlock(&udc->lock);
        }

        if (status & DC_IEBRST) {
                dev_dbg(udc->isp->dev, "%s(BRST)\n", __func__);

                isp1760_udc_reset(udc);
        }

        for (i = 0; i <= 7; ++i) {
                struct isp1760_ep *ep = &udc->ep[i*2];

                if (status & DC_IEPTX(i)) {
                        dev_dbg(udc->isp->dev, "%s(EPTX%u)\n", __func__, i);
                        isp1760_ep_tx_complete(ep);
                }

                if (status & DC_IEPRX(i)) {
                        dev_dbg(udc->isp->dev, "%s(EPRX%u)\n", __func__, i);
                        isp1760_ep_rx_ready(i ? ep - 1 : ep);
                }
        }

        if (status & DC_IEP0SETUP) {
                dev_dbg(udc->isp->dev, "%s(EP0SETUP)\n", __func__);

                isp1760_ep0_setup(udc);
        }

        if (status & DC_IERESM) {
                dev_dbg(udc->isp->dev, "%s(RESM)\n", __func__);
                isp1760_udc_resume(udc);
        }

        if (status & DC_IESUSP) {
                dev_dbg(udc->isp->dev, "%s(SUSP)\n", __func__);

                spin_lock(&udc->lock);
                if (!(isp1760_udc_read(udc, DC_MODE) & DC_VBUSSTAT))
                        isp1760_udc_disconnect(udc);
                else
                        isp1760_udc_suspend(udc);
                spin_unlock(&udc->lock);
        }

        if (status & DC_IEHS_STA) {
                dev_dbg(udc->isp->dev, "%s(HS_STA)\n", __func__);
                udc->gadget.speed = USB_SPEED_HIGH;
        }

        return status ? IRQ_HANDLED : IRQ_NONE;
}

static void isp1760_udc_vbus_poll(struct timer_list *t)
{
        struct isp1760_udc *udc = from_timer(udc, t, vbus_timer);
        unsigned long flags;

        spin_lock_irqsave(&udc->lock, flags);

        if (!(isp1760_udc_read(udc, DC_MODE) & DC_VBUSSTAT))
                isp1760_udc_disconnect(udc);
        else if (udc->gadget.state >= USB_STATE_POWERED)
                mod_timer(&udc->vbus_timer,
                          jiffies + ISP1760_VBUS_POLL_INTERVAL);

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

/* -----------------------------------------------------------------------------
 * Registration
 */

static void isp1760_udc_init_eps(struct isp1760_udc *udc)
{
        unsigned int i;

        INIT_LIST_HEAD(&udc->gadget.ep_list);

        for (i = 0; i < ARRAY_SIZE(udc->ep); ++i) {
                struct isp1760_ep *ep = &udc->ep[i];
                unsigned int ep_num = (i + 1) / 2;
                bool is_in = !(i & 1);

                ep->udc = udc;

                INIT_LIST_HEAD(&ep->queue);

                ep->addr = (ep_num && is_in ? USB_DIR_IN : USB_DIR_OUT)
                         | ep_num;
                ep->desc = NULL;

                sprintf(ep->name, "ep%u%s", ep_num,
                        ep_num ? (is_in ? "in" : "out") : "");

                ep->ep.ops = &isp1760_ep_ops;
                ep->ep.name = ep->name;

                /*
                 * Hardcode the maximum packet sizes for now, to 64 bytes for
                 * the control endpoint and 512 bytes for all other endpoints.
                 * This fits in the 8kB FIFO without double-buffering.
                 */
                if (ep_num == 0) {
                        usb_ep_set_maxpacket_limit(&ep->ep, 64);
                        ep->ep.caps.type_control = true;
                        ep->ep.caps.dir_in = true;
                        ep->ep.caps.dir_out = true;
                        ep->maxpacket = 64;
                        udc->gadget.ep0 = &ep->ep;
                } else {
                        usb_ep_set_maxpacket_limit(&ep->ep, 512);
                        ep->ep.caps.type_iso = true;
                        ep->ep.caps.type_bulk = true;
                        ep->ep.caps.type_int = true;
                        ep->maxpacket = 0;
                        list_add_tail(&ep->ep.ep_list, &udc->gadget.ep_list);
                }

                if (is_in)
                        ep->ep.caps.dir_in = true;
                else
                        ep->ep.caps.dir_out = true;
        }
}

static int isp1760_udc_init(struct isp1760_udc *udc)
{
        u16 scratch;
        u32 chipid;

        /*
         * Check that the controller is present by writing to the scratch
         * register, modifying the bus pattern by reading from the chip ID
         * register, and reading the scratch register value back. The chip ID
         * and scratch register contents must match the expected values.
         */
        isp1760_udc_write(udc, DC_SCRATCH, 0xbabe);
        chipid = isp1760_udc_read(udc, DC_CHIPID);
        scratch = isp1760_udc_read(udc, DC_SCRATCH);

        if (scratch != 0xbabe) {
                dev_err(udc->isp->dev,
                        "udc: scratch test failed (0x%04x/0x%08x)\n",
                        scratch, chipid);
                return -ENODEV;
        }

        if (chipid != 0x00011582 && chipid != 0x00158210) {
                dev_err(udc->isp->dev, "udc: invalid chip ID 0x%08x\n", chipid);
                return -ENODEV;
        }

        /* Reset the device controller. */
        isp1760_udc_write(udc, DC_MODE, DC_SFRESET);
        usleep_range(10000, 11000);
        isp1760_udc_write(udc, DC_MODE, 0);
        usleep_range(10000, 11000);

        return 0;
}

int isp1760_udc_register(struct isp1760_device *isp, int irq,
                         unsigned long irqflags)
{
        struct isp1760_udc *udc = &isp->udc;
        int ret;

        udc->irq = -1;
        udc->isp = isp;
        udc->regs = isp->regs;

        spin_lock_init(&udc->lock);
        timer_setup(&udc->vbus_timer, isp1760_udc_vbus_poll, 0);

        ret = isp1760_udc_init(udc);
        if (ret < 0)
                return ret;

        udc->irqname = kasprintf(GFP_KERNEL, "%s (udc)", dev_name(isp->dev));
        if (!udc->irqname)
                return -ENOMEM;

        ret = request_irq(irq, isp1760_udc_irq, IRQF_SHARED | irqflags,
                          udc->irqname, udc);
        if (ret < 0)
                goto error;

        udc->irq = irq;

        /*
         * Initialize the gadget static fields and register its device. Gadget
         * fields that vary during the life time of the gadget are initialized
         * by the UDC core.
         */
        udc->gadget.ops = &isp1760_udc_ops;
        udc->gadget.speed = USB_SPEED_UNKNOWN;
        udc->gadget.max_speed = USB_SPEED_HIGH;
        udc->gadget.name = "isp1761_udc";

        isp1760_udc_init_eps(udc);

        ret = usb_add_gadget_udc(isp->dev, &udc->gadget);
        if (ret < 0)
                goto error;

        return 0;

error:
        if (udc->irq >= 0)
                free_irq(udc->irq, udc);
        kfree(udc->irqname);

        return ret;
}

void isp1760_udc_unregister(struct isp1760_device *isp)
{
        struct isp1760_udc *udc = &isp->udc;

        if (!udc->isp)
                return;

        usb_del_gadget_udc(&udc->gadget);

        free_irq(udc->irq, udc);
        kfree(udc->irqname);
}