// SPDX-License-Identifier: GPL-2.0
/*
 * MAX3421 Host Controller driver for USB.
 *
 * Author: David Mosberger-Tang <davidm@egauge.net>
 *
 * (C) Copyright 2014 David Mosberger-Tang <davidm@egauge.net>
 *
 * MAX3421 is a chip implementing a USB 2.0 Full-/Low-Speed host
 * controller on a SPI bus.
 *
 * Based on:
 *      o MAX3421E datasheet
 *              https://datasheets.maximintegrated.com/en/ds/MAX3421E.pdf
 *      o MAX3421E Programming Guide
 *              https://www.hdl.co.jp/ftpdata/utl-001/AN3785.pdf
 *      o gadget/dummy_hcd.c
 *              For USB HCD implementation.
 *      o Arduino MAX3421 driver
 *           https://github.com/felis/USB_Host_Shield_2.0/blob/master/Usb.cpp
 *
 * This file is licenced under the GPL v2.
 *
 * Important note on worst-case (full-speed) packet size constraints
 * (See USB 2.0 Section 5.6.3 and following):
 *
 *      - control:        64 bytes
 *      - isochronous:  1023 bytes
 *      - interrupt:      64 bytes
 *      - bulk:           64 bytes
 *
 * Since the MAX3421 FIFO size is 64 bytes, we do not have to work about
 * multi-FIFO writes/reads for a single USB packet *except* for isochronous
 * transfers.  We don't support isochronous transfers at this time, so we
 * just assume that a USB packet always fits into a single FIFO buffer.
 *
 * NOTE: The June 2006 version of "MAX3421E Programming Guide"
 * (AN3785) has conflicting info for the RCVDAVIRQ bit:
 *
 *      The description of RCVDAVIRQ says "The CPU *must* clear
 *      this IRQ bit (by writing a 1 to it) before reading the
 *      RCVFIFO data.
 *
 * However, the earlier section on "Programming BULK-IN
 * Transfers" says * that:
 *
 *      After the CPU retrieves the data, it clears the
 *      RCVDAVIRQ bit.
 *
 * The December 2006 version has been corrected and it consistently
 * states the second behavior is the correct one.
 *
 * Synchronous SPI transactions sleep so we can't perform any such
 * transactions while holding a spin-lock (and/or while interrupts are
 * masked).  To achieve this, all SPI transactions are issued from a
 * single thread (max3421_spi_thread).
 */

#include <linux/jiffies.h>
#include <linux/module.h>
#include <linux/spi/spi.h>
#include <linux/usb.h>
#include <linux/usb/hcd.h>
#include <linux/of.h>

#include <linux/platform_data/max3421-hcd.h>

#define DRIVER_DESC     "MAX3421 USB Host-Controller Driver"
#define DRIVER_VERSION  "1.0"

/* 11-bit counter that wraps around (USB 2.0 Section 8.3.3): */
#define USB_MAX_FRAME_NUMBER    0x7ff
#define USB_MAX_RETRIES         3 /* # of retries before error is reported */

#define POWER_BUDGET    500     /* in mA; use 8 for low-power port testing */

/* Port-change mask: */
#define PORT_C_MASK     ((USB_PORT_STAT_C_CONNECTION |  \
                          USB_PORT_STAT_C_ENABLE |      \
                          USB_PORT_STAT_C_SUSPEND |     \
                          USB_PORT_STAT_C_OVERCURRENT | \
                          USB_PORT_STAT_C_RESET) << 16)

#define MAX3421_GPOUT_COUNT     8

enum max3421_rh_state {
        MAX3421_RH_RESET,
        MAX3421_RH_SUSPENDED,
        MAX3421_RH_RUNNING
};

enum pkt_state {
        PKT_STATE_SETUP,        /* waiting to send setup packet to ctrl pipe */
        PKT_STATE_TRANSFER,     /* waiting to xfer transfer_buffer */
        PKT_STATE_TERMINATE     /* waiting to terminate control transfer */
};

enum scheduling_pass {
        SCHED_PASS_PERIODIC,
        SCHED_PASS_NON_PERIODIC,
        SCHED_PASS_DONE
};

/* Bit numbers for max3421_hcd->todo: */
enum {
        ENABLE_IRQ = 0,
        RESET_HCD,
        RESET_PORT,
        CHECK_UNLINK,
        IOPIN_UPDATE
};

struct max3421_dma_buf {
        u8 data[2];
};

struct max3421_hcd {
        spinlock_t lock;

        struct task_struct *spi_thread;

        enum max3421_rh_state rh_state;
        /* lower 16 bits contain port status, upper 16 bits the change mask: */
        u32 port_status;

        unsigned active:1;

        struct list_head ep_list;       /* list of EP's with work */

        /*
         * The following are owned by spi_thread (may be accessed by
         * SPI-thread without acquiring the HCD lock:
         */
        u8 rev;                         /* chip revision */
        u16 frame_number;
        /*
         * kmalloc'd buffers guaranteed to be in separate (DMA)
         * cache-lines:
         */
        struct max3421_dma_buf *tx;
        struct max3421_dma_buf *rx;
        /*
         * URB we're currently processing.  Must not be reset to NULL
         * unless MAX3421E chip is idle:
         */
        struct urb *curr_urb;
        enum scheduling_pass sched_pass;
        int urb_done;                   /* > 0 -> no errors, < 0: errno */
        size_t curr_len;
        u8 hien;
        u8 mode;
        u8 iopins[2];
        unsigned long todo;
#ifdef DEBUG
        unsigned long err_stat[16];
#endif
};

struct max3421_ep {
        struct usb_host_endpoint *ep;
        struct list_head ep_list;
        u32 naks;
        u16 last_active;                /* frame # this ep was last active */
        enum pkt_state pkt_state;
        u8 retries;
        u8 retransmit;                  /* packet needs retransmission */
};

#define MAX3421_FIFO_SIZE       64

#define MAX3421_SPI_DIR_RD      0       /* read register from MAX3421 */
#define MAX3421_SPI_DIR_WR      1       /* write register to MAX3421 */

/* SPI commands: */
#define MAX3421_SPI_DIR_SHIFT   1
#define MAX3421_SPI_REG_SHIFT   3

#define MAX3421_REG_RCVFIFO     1
#define MAX3421_REG_SNDFIFO     2
#define MAX3421_REG_SUDFIFO     4
#define MAX3421_REG_RCVBC       6
#define MAX3421_REG_SNDBC       7
#define MAX3421_REG_USBIRQ      13
#define MAX3421_REG_USBIEN      14
#define MAX3421_REG_USBCTL      15
#define MAX3421_REG_CPUCTL      16
#define MAX3421_REG_PINCTL      17
#define MAX3421_REG_REVISION    18
#define MAX3421_REG_IOPINS1     20
#define MAX3421_REG_IOPINS2     21
#define MAX3421_REG_GPINIRQ     22
#define MAX3421_REG_GPINIEN     23
#define MAX3421_REG_GPINPOL     24
#define MAX3421_REG_HIRQ        25
#define MAX3421_REG_HIEN        26
#define MAX3421_REG_MODE        27
#define MAX3421_REG_PERADDR     28
#define MAX3421_REG_HCTL        29
#define MAX3421_REG_HXFR        30
#define MAX3421_REG_HRSL        31

enum {
        MAX3421_USBIRQ_OSCOKIRQ_BIT = 0,
        MAX3421_USBIRQ_NOVBUSIRQ_BIT = 5,
        MAX3421_USBIRQ_VBUSIRQ_BIT
};

enum {
        MAX3421_CPUCTL_IE_BIT = 0,
        MAX3421_CPUCTL_PULSEWID0_BIT = 6,
        MAX3421_CPUCTL_PULSEWID1_BIT
};

enum {
        MAX3421_USBCTL_PWRDOWN_BIT = 4,
        MAX3421_USBCTL_CHIPRES_BIT
};

enum {
        MAX3421_PINCTL_GPXA_BIT = 0,
        MAX3421_PINCTL_GPXB_BIT,
        MAX3421_PINCTL_POSINT_BIT,
        MAX3421_PINCTL_INTLEVEL_BIT,
        MAX3421_PINCTL_FDUPSPI_BIT,
        MAX3421_PINCTL_EP0INAK_BIT,
        MAX3421_PINCTL_EP2INAK_BIT,
        MAX3421_PINCTL_EP3INAK_BIT,
};

enum {
        MAX3421_HI_BUSEVENT_BIT = 0,    /* bus-reset/-resume */
        MAX3421_HI_RWU_BIT,             /* remote wakeup */
        MAX3421_HI_RCVDAV_BIT,          /* receive FIFO data available */
        MAX3421_HI_SNDBAV_BIT,          /* send buffer available */
        MAX3421_HI_SUSDN_BIT,           /* suspend operation done */
        MAX3421_HI_CONDET_BIT,          /* peripheral connect/disconnect */
        MAX3421_HI_FRAME_BIT,           /* frame generator */
        MAX3421_HI_HXFRDN_BIT,          /* host transfer done */
};

enum {
        MAX3421_HCTL_BUSRST_BIT = 0,
        MAX3421_HCTL_FRMRST_BIT,
        MAX3421_HCTL_SAMPLEBUS_BIT,
        MAX3421_HCTL_SIGRSM_BIT,
        MAX3421_HCTL_RCVTOG0_BIT,
        MAX3421_HCTL_RCVTOG1_BIT,
        MAX3421_HCTL_SNDTOG0_BIT,
        MAX3421_HCTL_SNDTOG1_BIT
};

enum {
        MAX3421_MODE_HOST_BIT = 0,
        MAX3421_MODE_LOWSPEED_BIT,
        MAX3421_MODE_HUBPRE_BIT,
        MAX3421_MODE_SOFKAENAB_BIT,
        MAX3421_MODE_SEPIRQ_BIT,
        MAX3421_MODE_DELAYISO_BIT,
        MAX3421_MODE_DMPULLDN_BIT,
        MAX3421_MODE_DPPULLDN_BIT
};

enum {
        MAX3421_HRSL_OK = 0,
        MAX3421_HRSL_BUSY,
        MAX3421_HRSL_BADREQ,
        MAX3421_HRSL_UNDEF,
        MAX3421_HRSL_NAK,
        MAX3421_HRSL_STALL,
        MAX3421_HRSL_TOGERR,
        MAX3421_HRSL_WRONGPID,
        MAX3421_HRSL_BADBC,
        MAX3421_HRSL_PIDERR,
        MAX3421_HRSL_PKTERR,
        MAX3421_HRSL_CRCERR,
        MAX3421_HRSL_KERR,
        MAX3421_HRSL_JERR,
        MAX3421_HRSL_TIMEOUT,
        MAX3421_HRSL_BABBLE,
        MAX3421_HRSL_RESULT_MASK = 0xf,
        MAX3421_HRSL_RCVTOGRD_BIT = 4,
        MAX3421_HRSL_SNDTOGRD_BIT,
        MAX3421_HRSL_KSTATUS_BIT,
        MAX3421_HRSL_JSTATUS_BIT
};

/* Return same error-codes as ohci.h:cc_to_error: */
static const int hrsl_to_error[] = {
        [MAX3421_HRSL_OK] =             0,
        [MAX3421_HRSL_BUSY] =           -EINVAL,
        [MAX3421_HRSL_BADREQ] =         -EINVAL,
        [MAX3421_HRSL_UNDEF] =          -EINVAL,
        [MAX3421_HRSL_NAK] =            -EAGAIN,
        [MAX3421_HRSL_STALL] =          -EPIPE,
        [MAX3421_HRSL_TOGERR] =         -EILSEQ,
        [MAX3421_HRSL_WRONGPID] =       -EPROTO,
        [MAX3421_HRSL_BADBC] =          -EREMOTEIO,
        [MAX3421_HRSL_PIDERR] =         -EPROTO,
        [MAX3421_HRSL_PKTERR] =         -EPROTO,
        [MAX3421_HRSL_CRCERR] =         -EILSEQ,
        [MAX3421_HRSL_KERR] =           -EIO,
        [MAX3421_HRSL_JERR] =           -EIO,
        [MAX3421_HRSL_TIMEOUT] =        -ETIME,
        [MAX3421_HRSL_BABBLE] =         -EOVERFLOW
};

/*
 * See https://www.beyondlogic.org/usbnutshell/usb4.shtml#Control for a
 * reasonable overview of how control transfers use the IN/OUT
 * tokens.
 */
#define MAX3421_HXFR_BULK_IN(ep)        (0x00 | (ep))   /* bulk or interrupt */
#define MAX3421_HXFR_SETUP               0x10
#define MAX3421_HXFR_BULK_OUT(ep)       (0x20 | (ep))   /* bulk or interrupt */
#define MAX3421_HXFR_ISO_IN(ep)         (0x40 | (ep))
#define MAX3421_HXFR_ISO_OUT(ep)        (0x60 | (ep))
#define MAX3421_HXFR_HS_IN               0x80           /* handshake in */
#define MAX3421_HXFR_HS_OUT              0xa0           /* handshake out */

#define field(val, bit) ((val) << (bit))

static inline s16
frame_diff(u16 left, u16 right)
{
        return ((unsigned) (left - right)) % (USB_MAX_FRAME_NUMBER + 1);
}

static inline struct max3421_hcd *
hcd_to_max3421(struct usb_hcd *hcd)
{
        return (struct max3421_hcd *) hcd->hcd_priv;
}

static inline struct usb_hcd *
max3421_to_hcd(struct max3421_hcd *max3421_hcd)
{
        return container_of((void *) max3421_hcd, struct usb_hcd, hcd_priv);
}

static u8
spi_rd8(struct usb_hcd *hcd, unsigned int reg)
{
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        struct spi_device *spi = to_spi_device(hcd->self.controller);
        struct spi_transfer transfer;
        struct spi_message msg;

        memset(&transfer, 0, sizeof(transfer));

        spi_message_init(&msg);

        max3421_hcd->tx->data[0] =
                (field(reg, MAX3421_SPI_REG_SHIFT) |
                 field(MAX3421_SPI_DIR_RD, MAX3421_SPI_DIR_SHIFT));

        transfer.tx_buf = max3421_hcd->tx->data;
        transfer.rx_buf = max3421_hcd->rx->data;
        transfer.len = 2;

        spi_message_add_tail(&transfer, &msg);
        spi_sync(spi, &msg);

        return max3421_hcd->rx->data[1];
}

static void
spi_wr8(struct usb_hcd *hcd, unsigned int reg, u8 val)
{
        struct spi_device *spi = to_spi_device(hcd->self.controller);
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        struct spi_transfer transfer;
        struct spi_message msg;

        memset(&transfer, 0, sizeof(transfer));

        spi_message_init(&msg);

        max3421_hcd->tx->data[0] =
                (field(reg, MAX3421_SPI_REG_SHIFT) |
                 field(MAX3421_SPI_DIR_WR, MAX3421_SPI_DIR_SHIFT));
        max3421_hcd->tx->data[1] = val;

        transfer.tx_buf = max3421_hcd->tx->data;
        transfer.len = 2;

        spi_message_add_tail(&transfer, &msg);
        spi_sync(spi, &msg);
}

static void
spi_rd_buf(struct usb_hcd *hcd, unsigned int reg, void *buf, size_t len)
{
        struct spi_device *spi = to_spi_device(hcd->self.controller);
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        struct spi_transfer transfer[2];
        struct spi_message msg;

        memset(transfer, 0, sizeof(transfer));

        spi_message_init(&msg);

        max3421_hcd->tx->data[0] =
                (field(reg, MAX3421_SPI_REG_SHIFT) |
                 field(MAX3421_SPI_DIR_RD, MAX3421_SPI_DIR_SHIFT));
        transfer[0].tx_buf = max3421_hcd->tx->data;
        transfer[0].len = 1;

        transfer[1].rx_buf = buf;
        transfer[1].len = len;

        spi_message_add_tail(&transfer[0], &msg);
        spi_message_add_tail(&transfer[1], &msg);
        spi_sync(spi, &msg);
}

static void
spi_wr_buf(struct usb_hcd *hcd, unsigned int reg, void *buf, size_t len)
{
        struct spi_device *spi = to_spi_device(hcd->self.controller);
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        struct spi_transfer transfer[2];
        struct spi_message msg;

        memset(transfer, 0, sizeof(transfer));

        spi_message_init(&msg);

        max3421_hcd->tx->data[0] =
                (field(reg, MAX3421_SPI_REG_SHIFT) |
                 field(MAX3421_SPI_DIR_WR, MAX3421_SPI_DIR_SHIFT));

        transfer[0].tx_buf = max3421_hcd->tx->data;
        transfer[0].len = 1;

        transfer[1].tx_buf = buf;
        transfer[1].len = len;

        spi_message_add_tail(&transfer[0], &msg);
        spi_message_add_tail(&transfer[1], &msg);
        spi_sync(spi, &msg);
}

/*
 * Figure out the correct setting for the LOWSPEED and HUBPRE mode
 * bits.  The HUBPRE bit needs to be set when MAX3421E operates at
 * full speed, but it's talking to a low-speed device (i.e., through a
 * hub).  Setting that bit ensures that every low-speed packet is
 * preceded by a full-speed PRE PID.  Possible configurations:
 *
 * Hub speed:   Device speed:   =>      LOWSPEED bit:   HUBPRE bit:
 *      FULL    FULL            =>      0               0
 *      FULL    LOW             =>      1               1
 *      LOW     LOW             =>      1               0
 *      LOW     FULL            =>      1               0
 */
static void
max3421_set_speed(struct usb_hcd *hcd, struct usb_device *dev)
{
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        u8 mode_lowspeed, mode_hubpre, mode = max3421_hcd->mode;

        mode_lowspeed = BIT(MAX3421_MODE_LOWSPEED_BIT);
        mode_hubpre   = BIT(MAX3421_MODE_HUBPRE_BIT);
        if (max3421_hcd->port_status & USB_PORT_STAT_LOW_SPEED) {
                mode |=  mode_lowspeed;
                mode &= ~mode_hubpre;
        } else if (dev->speed == USB_SPEED_LOW) {
                mode |= mode_lowspeed | mode_hubpre;
        } else {
                mode &= ~(mode_lowspeed | mode_hubpre);
        }
        if (mode != max3421_hcd->mode) {
                max3421_hcd->mode = mode;
                spi_wr8(hcd, MAX3421_REG_MODE, max3421_hcd->mode);
        }

}

/*
 * Caller must NOT hold HCD spinlock.
 */
static void
max3421_set_address(struct usb_hcd *hcd, struct usb_device *dev, int epnum)
{
        int rcvtog, sndtog;
        u8 hctl;

        /* setup new endpoint's toggle bits: */
        rcvtog = usb_gettoggle(dev, epnum, 0);
        sndtog = usb_gettoggle(dev, epnum, 1);
        hctl = (BIT(rcvtog + MAX3421_HCTL_RCVTOG0_BIT) |
                BIT(sndtog + MAX3421_HCTL_SNDTOG0_BIT));

        spi_wr8(hcd, MAX3421_REG_HCTL, hctl);

        /*
         * Note: devnum for one and the same device can change during
         * address-assignment so it's best to just always load the
         * address whenever the end-point changed/was forced.
         */
        spi_wr8(hcd, MAX3421_REG_PERADDR, dev->devnum);
}

static int
max3421_ctrl_setup(struct usb_hcd *hcd, struct urb *urb)
{
        spi_wr_buf(hcd, MAX3421_REG_SUDFIFO, urb->setup_packet, 8);
        return MAX3421_HXFR_SETUP;
}

static int
max3421_transfer_in(struct usb_hcd *hcd, struct urb *urb)
{
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        int epnum = usb_pipeendpoint(urb->pipe);

        max3421_hcd->curr_len = 0;
        max3421_hcd->hien |= BIT(MAX3421_HI_RCVDAV_BIT);
        return MAX3421_HXFR_BULK_IN(epnum);
}

static int
max3421_transfer_out(struct usb_hcd *hcd, struct urb *urb, int fast_retransmit)
{
        struct spi_device *spi = to_spi_device(hcd->self.controller);
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        int epnum = usb_pipeendpoint(urb->pipe);
        u32 max_packet;
        void *src;

        src = urb->transfer_buffer + urb->actual_length;

        if (fast_retransmit) {
                if (max3421_hcd->rev == 0x12) {
                        /* work around rev 0x12 bug: */
                        spi_wr8(hcd, MAX3421_REG_SNDBC, 0);
                        spi_wr8(hcd, MAX3421_REG_SNDFIFO, ((u8 *) src)[0]);
                        spi_wr8(hcd, MAX3421_REG_SNDBC, max3421_hcd->curr_len);
                }
                return MAX3421_HXFR_BULK_OUT(epnum);
        }

        max_packet = usb_maxpacket(urb->dev, urb->pipe);

        if (max_packet > MAX3421_FIFO_SIZE) {
                /*
                 * We do not support isochronous transfers at this
                 * time.
                 */
                dev_err(&spi->dev,
                        "%s: packet-size of %u too big (limit is %u bytes)",
                        __func__, max_packet, MAX3421_FIFO_SIZE);
                max3421_hcd->urb_done = -EMSGSIZE;
                return -EMSGSIZE;
        }
        max3421_hcd->curr_len = min((urb->transfer_buffer_length -
                                     urb->actual_length), max_packet);

        spi_wr_buf(hcd, MAX3421_REG_SNDFIFO, src, max3421_hcd->curr_len);
        spi_wr8(hcd, MAX3421_REG_SNDBC, max3421_hcd->curr_len);
        return MAX3421_HXFR_BULK_OUT(epnum);
}

/*
 * Issue the next host-transfer command.
 * Caller must NOT hold HCD spinlock.
 */
static void
max3421_next_transfer(struct usb_hcd *hcd, int fast_retransmit)
{
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        struct urb *urb = max3421_hcd->curr_urb;
        struct max3421_ep *max3421_ep;
        int cmd = -EINVAL;

        if (!urb)
                return; /* nothing to do */

        max3421_ep = urb->ep->hcpriv;

        switch (max3421_ep->pkt_state) {
        case PKT_STATE_SETUP:
                cmd = max3421_ctrl_setup(hcd, urb);
                break;

        case PKT_STATE_TRANSFER:
                if (usb_urb_dir_in(urb))
                        cmd = max3421_transfer_in(hcd, urb);
                else
                        cmd = max3421_transfer_out(hcd, urb, fast_retransmit);
                break;

        case PKT_STATE_TERMINATE:
                /*
                 * IN transfers are terminated with HS_OUT token,
                 * OUT transfers with HS_IN:
                 */
                if (usb_urb_dir_in(urb))
                        cmd = MAX3421_HXFR_HS_OUT;
                else
                        cmd = MAX3421_HXFR_HS_IN;
                break;
        }

        if (cmd < 0)
                return;

        /* issue the command and wait for host-xfer-done interrupt: */

        spi_wr8(hcd, MAX3421_REG_HXFR, cmd);
        max3421_hcd->hien |= BIT(MAX3421_HI_HXFRDN_BIT);
}

/*
 * Find the next URB to process and start its execution.
 *
 * At this time, we do not anticipate ever connecting a USB hub to the
 * MAX3421 chip, so at most USB device can be connected and we can use
 * a simplistic scheduler: at the start of a frame, schedule all
 * periodic transfers.  Once that is done, use the remainder of the
 * frame to process non-periodic (bulk & control) transfers.
 *
 * Preconditions:
 * o Caller must NOT hold HCD spinlock.
 * o max3421_hcd->curr_urb MUST BE NULL.
 * o MAX3421E chip must be idle.
 */
static int
max3421_select_and_start_urb(struct usb_hcd *hcd)
{
        struct spi_device *spi = to_spi_device(hcd->self.controller);
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        struct urb *urb, *curr_urb = NULL;
        struct max3421_ep *max3421_ep;
        int epnum;
        struct usb_host_endpoint *ep;
        struct list_head *pos;
        unsigned long flags;

        spin_lock_irqsave(&max3421_hcd->lock, flags);

        for (;
             max3421_hcd->sched_pass < SCHED_PASS_DONE;
             ++max3421_hcd->sched_pass)
                list_for_each(pos, &max3421_hcd->ep_list) {
                        urb = NULL;
                        max3421_ep = container_of(pos, struct max3421_ep,
                                                  ep_list);
                        ep = max3421_ep->ep;

                        switch (usb_endpoint_type(&ep->desc)) {
                        case USB_ENDPOINT_XFER_ISOC:
                        case USB_ENDPOINT_XFER_INT:
                                if (max3421_hcd->sched_pass !=
                                    SCHED_PASS_PERIODIC)
                                        continue;
                                break;

                        case USB_ENDPOINT_XFER_CONTROL:
                        case USB_ENDPOINT_XFER_BULK:
                                if (max3421_hcd->sched_pass !=
                                    SCHED_PASS_NON_PERIODIC)
                                        continue;
                                break;
                        }

                        if (list_empty(&ep->urb_list))
                                continue;       /* nothing to do */
                        urb = list_first_entry(&ep->urb_list, struct urb,
                                               urb_list);
                        if (urb->unlinked) {
                                dev_dbg(&spi->dev, "%s: URB %p unlinked=%d",
                                        __func__, urb, urb->unlinked);
                                max3421_hcd->curr_urb = urb;
                                max3421_hcd->urb_done = 1;
                                spin_unlock_irqrestore(&max3421_hcd->lock,
                                                       flags);
                                return 1;
                        }

                        switch (usb_endpoint_type(&ep->desc)) {
                        case USB_ENDPOINT_XFER_CONTROL:
                                /*
                                 * Allow one control transaction per
                                 * frame per endpoint:
                                 */
                                if (frame_diff(max3421_ep->last_active,
                                               max3421_hcd->frame_number) == 0)
                                        continue;
                                break;

                        case USB_ENDPOINT_XFER_BULK:
                                if (max3421_ep->retransmit
                                    && (frame_diff(max3421_ep->last_active,
                                                   max3421_hcd->frame_number)
                                        == 0))
                                        /*
                                         * We already tried this EP
                                         * during this frame and got a
                                         * NAK or error; wait for next frame
                                         */
                                        continue;
                                break;

                        case USB_ENDPOINT_XFER_ISOC:
                        case USB_ENDPOINT_XFER_INT:
                                if (frame_diff(max3421_hcd->frame_number,
                                               max3421_ep->last_active)
                                    < urb->interval)
                                        /*
                                         * We already processed this
                                         * end-point in the current
                                         * frame
                                         */
                                        continue;
                                break;
                        }

                        /* move current ep to tail: */
                        list_move_tail(pos, &max3421_hcd->ep_list);
                        curr_urb = urb;
                        goto done;
                }
done:
        if (!curr_urb) {
                spin_unlock_irqrestore(&max3421_hcd->lock, flags);
                return 0;
        }

        urb = max3421_hcd->curr_urb = curr_urb;
        epnum = usb_endpoint_num(&urb->ep->desc);
        if (max3421_ep->retransmit)
                /* restart (part of) a USB transaction: */
                max3421_ep->retransmit = 0;
        else {
                /* start USB transaction: */
                if (usb_endpoint_xfer_control(&ep->desc)) {
                        /*
                         * See USB 2.0 spec section 8.6.1
                         * Initialization via SETUP Token:
                         */
                        usb_settoggle(urb->dev, epnum, 0, 1);
                        usb_settoggle(urb->dev, epnum, 1, 1);
                        max3421_ep->pkt_state = PKT_STATE_SETUP;
                } else
                        max3421_ep->pkt_state = PKT_STATE_TRANSFER;
        }

        spin_unlock_irqrestore(&max3421_hcd->lock, flags);

        max3421_ep->last_active = max3421_hcd->frame_number;
        max3421_set_address(hcd, urb->dev, epnum);
        max3421_set_speed(hcd, urb->dev);
        max3421_next_transfer(hcd, 0);
        return 1;
}

/*
 * Check all endpoints for URBs that got unlinked.
 *
 * Caller must NOT hold HCD spinlock.
 */
static int
max3421_check_unlink(struct usb_hcd *hcd)
{
        struct spi_device *spi = to_spi_device(hcd->self.controller);
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        struct max3421_ep *max3421_ep;
        struct usb_host_endpoint *ep;
        struct urb *urb, *next;
        unsigned long flags;
        int retval = 0;

        spin_lock_irqsave(&max3421_hcd->lock, flags);
        list_for_each_entry(max3421_ep, &max3421_hcd->ep_list, ep_list) {
                ep = max3421_ep->ep;
                list_for_each_entry_safe(urb, next, &ep->urb_list, urb_list) {
                        if (urb->unlinked) {
                                retval = 1;
                                dev_dbg(&spi->dev, "%s: URB %p unlinked=%d",
                                        __func__, urb, urb->unlinked);
                                if (urb == max3421_hcd->curr_urb) {
                                        max3421_hcd->urb_done = 1;
                                        max3421_hcd->hien &= ~(BIT(MAX3421_HI_HXFRDN_BIT) |
                                                               BIT(MAX3421_HI_RCVDAV_BIT));
                                } else {
                                        usb_hcd_unlink_urb_from_ep(hcd, urb);
                                        spin_unlock_irqrestore(&max3421_hcd->lock,
                                                               flags);
                                        usb_hcd_giveback_urb(hcd, urb, 0);
                                        spin_lock_irqsave(&max3421_hcd->lock, flags);
                                }
                        }
                }
        }
        spin_unlock_irqrestore(&max3421_hcd->lock, flags);
        return retval;
}

/*
 * Caller must NOT hold HCD spinlock.
 */
static void
max3421_slow_retransmit(struct usb_hcd *hcd)
{
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        struct urb *urb = max3421_hcd->curr_urb;
        struct max3421_ep *max3421_ep;

        max3421_ep = urb->ep->hcpriv;
        max3421_ep->retransmit = 1;
        max3421_hcd->curr_urb = NULL;
}

/*
 * Caller must NOT hold HCD spinlock.
 */
static void
max3421_recv_data_available(struct usb_hcd *hcd)
{
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        struct urb *urb = max3421_hcd->curr_urb;
        size_t remaining, transfer_size;
        u8 rcvbc;

        rcvbc = spi_rd8(hcd, MAX3421_REG_RCVBC);

        if (rcvbc > MAX3421_FIFO_SIZE)
                rcvbc = MAX3421_FIFO_SIZE;
        if (urb->actual_length >= urb->transfer_buffer_length)
                remaining = 0;
        else
                remaining = urb->transfer_buffer_length - urb->actual_length;
        transfer_size = rcvbc;
        if (transfer_size > remaining)
                transfer_size = remaining;
        if (transfer_size > 0) {
                void *dst = urb->transfer_buffer + urb->actual_length;

                spi_rd_buf(hcd, MAX3421_REG_RCVFIFO, dst, transfer_size);
                urb->actual_length += transfer_size;
                max3421_hcd->curr_len = transfer_size;
        }

        /* ack the RCVDAV irq now that the FIFO has been read: */
        spi_wr8(hcd, MAX3421_REG_HIRQ, BIT(MAX3421_HI_RCVDAV_BIT));
}

static void
max3421_handle_error(struct usb_hcd *hcd, u8 hrsl)
{
        struct spi_device *spi = to_spi_device(hcd->self.controller);
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        u8 result_code = hrsl & MAX3421_HRSL_RESULT_MASK;
        struct urb *urb = max3421_hcd->curr_urb;
        struct max3421_ep *max3421_ep = urb->ep->hcpriv;
        int switch_sndfifo;

        /*
         * If an OUT command results in any response other than OK
         * (i.e., error or NAK), we have to perform a dummy-write to
         * SNDBC so the FIFO gets switched back to us.  Otherwise, we
         * get out of sync with the SNDFIFO double buffer.
         */
        switch_sndfifo = (max3421_ep->pkt_state == PKT_STATE_TRANSFER &&
                          usb_urb_dir_out(urb));

        switch (result_code) {
        case MAX3421_HRSL_OK:
                return;                 /* this shouldn't happen */

        case MAX3421_HRSL_WRONGPID:     /* received wrong PID */
        case MAX3421_HRSL_BUSY:         /* SIE busy */
        case MAX3421_HRSL_BADREQ:       /* bad val in HXFR */
        case MAX3421_HRSL_UNDEF:        /* reserved */
        case MAX3421_HRSL_KERR:         /* K-state instead of response */
        case MAX3421_HRSL_JERR:         /* J-state instead of response */
                /*
                 * packet experienced an error that we cannot recover
                 * from; report error
                 */
                max3421_hcd->urb_done = hrsl_to_error[result_code];
                dev_dbg(&spi->dev, "%s: unexpected error HRSL=0x%02x",
                        __func__, hrsl);
                break;

        case MAX3421_HRSL_TOGERR:
                if (usb_urb_dir_in(urb))
                        ; /* don't do anything (device will switch toggle) */
                else {
                        /* flip the send toggle bit: */
                        int sndtog = (hrsl >> MAX3421_HRSL_SNDTOGRD_BIT) & 1;

                        sndtog ^= 1;
                        spi_wr8(hcd, MAX3421_REG_HCTL,
                                BIT(sndtog + MAX3421_HCTL_SNDTOG0_BIT));
                }
                fallthrough;
        case MAX3421_HRSL_BADBC:        /* bad byte count */
        case MAX3421_HRSL_PIDERR:       /* received PID is corrupted */
        case MAX3421_HRSL_PKTERR:       /* packet error (stuff, EOP) */
        case MAX3421_HRSL_CRCERR:       /* CRC error */
        case MAX3421_HRSL_BABBLE:       /* device talked too long */
        case MAX3421_HRSL_TIMEOUT:
                if (max3421_ep->retries++ < USB_MAX_RETRIES)
                        /* retry the packet again in the next frame */
                        max3421_slow_retransmit(hcd);
                else {
                        /* Based on ohci.h cc_to_err[]: */
                        max3421_hcd->urb_done = hrsl_to_error[result_code];
                        dev_dbg(&spi->dev, "%s: unexpected error HRSL=0x%02x",
                                __func__, hrsl);
                }
                break;

        case MAX3421_HRSL_STALL:
                dev_dbg(&spi->dev, "%s: unexpected error HRSL=0x%02x",
                        __func__, hrsl);
                max3421_hcd->urb_done = hrsl_to_error[result_code];
                break;

        case MAX3421_HRSL_NAK:
                /*
                 * Device wasn't ready for data or has no data
                 * available: retry the packet again.
                 */
                max3421_next_transfer(hcd, 1);
                switch_sndfifo = 0;
                break;
        }
        if (switch_sndfifo)
                spi_wr8(hcd, MAX3421_REG_SNDBC, 0);
}

/*
 * Caller must NOT hold HCD spinlock.
 */
static int
max3421_transfer_in_done(struct usb_hcd *hcd, struct urb *urb)
{
        struct spi_device *spi = to_spi_device(hcd->self.controller);
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        u32 max_packet;

        if (urb->actual_length >= urb->transfer_buffer_length)
                return 1;       /* read is complete, so we're done */

        /*
         * USB 2.0 Section 5.3.2 Pipes: packets must be full size
         * except for last one.
         */
        max_packet = usb_maxpacket(urb->dev, urb->pipe);
        if (max_packet > MAX3421_FIFO_SIZE) {
                /*
                 * We do not support isochronous transfers at this
                 * time...
                 */
                dev_err(&spi->dev,
                        "%s: packet-size of %u too big (limit is %u bytes)",
                        __func__, max_packet, MAX3421_FIFO_SIZE);
                return -EINVAL;
        }

        if (max3421_hcd->curr_len < max_packet) {
                if (urb->transfer_flags & URB_SHORT_NOT_OK) {
                        /*
                         * remaining > 0 and received an
                         * unexpected partial packet ->
                         * error
                         */
                        return -EREMOTEIO;
                } else
                        /* short read, but it's OK */
                        return 1;
        }
        return 0;       /* not done */
}

/*
 * Caller must NOT hold HCD spinlock.
 */
static int
max3421_transfer_out_done(struct usb_hcd *hcd, struct urb *urb)
{
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);

        urb->actual_length += max3421_hcd->curr_len;
        if (urb->actual_length < urb->transfer_buffer_length)
                return 0;
        if (urb->transfer_flags & URB_ZERO_PACKET) {
                /*
                 * Some hardware needs a zero-size packet at the end
                 * of a bulk-out transfer if the last transfer was a
                 * full-sized packet (i.e., such hardware use <
                 * max_packet as an indicator that the end of the
                 * packet has been reached).
                 */
                u32 max_packet = usb_maxpacket(urb->dev, urb->pipe);

                if (max3421_hcd->curr_len == max_packet)
                        return 0;
        }
        return 1;
}

/*
 * Caller must NOT hold HCD spinlock.
 */
static void
max3421_host_transfer_done(struct usb_hcd *hcd)
{
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        struct urb *urb = max3421_hcd->curr_urb;
        struct max3421_ep *max3421_ep;
        u8 result_code, hrsl;
        int urb_done = 0;

        max3421_hcd->hien &= ~(BIT(MAX3421_HI_HXFRDN_BIT) |
                               BIT(MAX3421_HI_RCVDAV_BIT));

        hrsl = spi_rd8(hcd, MAX3421_REG_HRSL);
        result_code = hrsl & MAX3421_HRSL_RESULT_MASK;

#ifdef DEBUG
        ++max3421_hcd->err_stat[result_code];
#endif

        max3421_ep = urb->ep->hcpriv;

        if (unlikely(result_code != MAX3421_HRSL_OK)) {
                max3421_handle_error(hcd, hrsl);
                return;
        }

        max3421_ep->naks = 0;
        max3421_ep->retries = 0;
        switch (max3421_ep->pkt_state) {

        case PKT_STATE_SETUP:
                if (urb->transfer_buffer_length > 0)
                        max3421_ep->pkt_state = PKT_STATE_TRANSFER;
                else
                        max3421_ep->pkt_state = PKT_STATE_TERMINATE;
                break;

        case PKT_STATE_TRANSFER:
                if (usb_urb_dir_in(urb))
                        urb_done = max3421_transfer_in_done(hcd, urb);
                else
                        urb_done = max3421_transfer_out_done(hcd, urb);
                if (urb_done > 0 && usb_pipetype(urb->pipe) == PIPE_CONTROL) {
                        /*
                         * We aren't really done - we still need to
                         * terminate the control transfer:
                         */
                        max3421_hcd->urb_done = urb_done = 0;
                        max3421_ep->pkt_state = PKT_STATE_TERMINATE;
                }
                break;

        case PKT_STATE_TERMINATE:
                urb_done = 1;
                break;
        }

        if (urb_done)
                max3421_hcd->urb_done = urb_done;
        else
                max3421_next_transfer(hcd, 0);
}

/*
 * Caller must NOT hold HCD spinlock.
 */
static void
max3421_detect_conn(struct usb_hcd *hcd)
{
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        unsigned int jk, have_conn = 0;
        u32 old_port_status, chg;
        unsigned long flags;
        u8 hrsl, mode;

        hrsl = spi_rd8(hcd, MAX3421_REG_HRSL);

        jk = ((((hrsl >> MAX3421_HRSL_JSTATUS_BIT) & 1) << 0) |
              (((hrsl >> MAX3421_HRSL_KSTATUS_BIT) & 1) << 1));

        mode = max3421_hcd->mode;

        switch (jk) {
        case 0x0: /* SE0: disconnect */
                /*
                 * Turn off SOFKAENAB bit to avoid getting interrupt
                 * every milli-second:
                 */
                mode &= ~BIT(MAX3421_MODE_SOFKAENAB_BIT);
                break;

        case 0x1: /* J=0,K=1: low-speed (in full-speed or vice versa) */
        case 0x2: /* J=1,K=0: full-speed (in full-speed or vice versa) */
                if (jk == 0x2)
                        /* need to switch to the other speed: */
                        mode ^= BIT(MAX3421_MODE_LOWSPEED_BIT);
                /* turn on SOFKAENAB bit: */
                mode |= BIT(MAX3421_MODE_SOFKAENAB_BIT);
                have_conn = 1;
                break;

        case 0x3: /* illegal */
                break;
        }

        max3421_hcd->mode = mode;
        spi_wr8(hcd, MAX3421_REG_MODE, max3421_hcd->mode);

        spin_lock_irqsave(&max3421_hcd->lock, flags);
        old_port_status = max3421_hcd->port_status;
        if (have_conn)
                max3421_hcd->port_status |=  USB_PORT_STAT_CONNECTION;
        else
                max3421_hcd->port_status &= ~USB_PORT_STAT_CONNECTION;
        if (mode & BIT(MAX3421_MODE_LOWSPEED_BIT))
                max3421_hcd->port_status |=  USB_PORT_STAT_LOW_SPEED;
        else
                max3421_hcd->port_status &= ~USB_PORT_STAT_LOW_SPEED;
        chg = (old_port_status ^ max3421_hcd->port_status);
        max3421_hcd->port_status |= chg << 16;
        spin_unlock_irqrestore(&max3421_hcd->lock, flags);
}

static irqreturn_t
max3421_irq_handler(int irq, void *dev_id)
{
        struct usb_hcd *hcd = dev_id;
        struct spi_device *spi = to_spi_device(hcd->self.controller);
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);

        if (max3421_hcd->spi_thread)
                wake_up_process(max3421_hcd->spi_thread);
        if (!test_and_set_bit(ENABLE_IRQ, &max3421_hcd->todo))
                disable_irq_nosync(spi->irq);
        return IRQ_HANDLED;
}

#ifdef DEBUG

static void
dump_eps(struct usb_hcd *hcd)
{
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        struct max3421_ep *max3421_ep;
        struct usb_host_endpoint *ep;
        char ubuf[512], *dp, *end;
        unsigned long flags;
        struct urb *urb;
        int epnum, ret;

        spin_lock_irqsave(&max3421_hcd->lock, flags);
        list_for_each_entry(max3421_ep, &max3421_hcd->ep_list, ep_list) {
                ep = max3421_ep->ep;

                dp = ubuf;
                end = dp + sizeof(ubuf);
                *dp = '\0';
                list_for_each_entry(urb, &ep->urb_list, urb_list) {
                        ret = scnprintf(dp, end - dp, " %p(%d.%s %d/%d)", urb,
                                        usb_pipetype(urb->pipe),
                                        usb_urb_dir_in(urb) ? "IN" : "OUT",
                                        urb->actual_length,
                                        urb->transfer_buffer_length);
                        if (ret == end - dp - 1)
                                break;  /* error or buffer full */
                        dp += ret;
                }

                epnum = usb_endpoint_num(&ep->desc);
                pr_info("EP%0u %u lst %04u rtr %u nak %6u rxmt %u: %s\n",
                        epnum, max3421_ep->pkt_state, max3421_ep->last_active,
                        max3421_ep->retries, max3421_ep->naks,
                        max3421_ep->retransmit, ubuf);
        }
        spin_unlock_irqrestore(&max3421_hcd->lock, flags);
}

#endif /* DEBUG */

/* Return zero if no work was performed, 1 otherwise.  */
static int
max3421_handle_irqs(struct usb_hcd *hcd)
{
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        u32 chg, old_port_status;
        unsigned long flags;
        u8 hirq;

        /*
         * Read and ack pending interrupts (CPU must never
         * clear SNDBAV directly and RCVDAV must be cleared by
         * max3421_recv_data_available()!):
         */
        hirq = spi_rd8(hcd, MAX3421_REG_HIRQ);
        hirq &= max3421_hcd->hien;
        if (!hirq)
                return 0;

        spi_wr8(hcd, MAX3421_REG_HIRQ,
                hirq & ~(BIT(MAX3421_HI_SNDBAV_BIT) |
                         BIT(MAX3421_HI_RCVDAV_BIT)));

        if (hirq & BIT(MAX3421_HI_FRAME_BIT)) {
                max3421_hcd->frame_number = ((max3421_hcd->frame_number + 1)
                                             & USB_MAX_FRAME_NUMBER);
                max3421_hcd->sched_pass = SCHED_PASS_PERIODIC;
        }

        if (hirq & BIT(MAX3421_HI_RCVDAV_BIT))
                max3421_recv_data_available(hcd);

        if (hirq & BIT(MAX3421_HI_HXFRDN_BIT))
                max3421_host_transfer_done(hcd);

        if (hirq & BIT(MAX3421_HI_CONDET_BIT))
                max3421_detect_conn(hcd);

        /*
         * Now process interrupts that may affect HCD state
         * other than the end-points:
         */
        spin_lock_irqsave(&max3421_hcd->lock, flags);

        old_port_status = max3421_hcd->port_status;
        if (hirq & BIT(MAX3421_HI_BUSEVENT_BIT)) {
                if (max3421_hcd->port_status & USB_PORT_STAT_RESET) {
                        /* BUSEVENT due to completion of Bus Reset */
                        max3421_hcd->port_status &= ~USB_PORT_STAT_RESET;
                        max3421_hcd->port_status |=  USB_PORT_STAT_ENABLE;
                } else {
                        /* BUSEVENT due to completion of Bus Resume */
                        pr_info("%s: BUSEVENT Bus Resume Done\n", __func__);
                }
        }
        if (hirq & BIT(MAX3421_HI_RWU_BIT))
                pr_info("%s: RWU\n", __func__);
        if (hirq & BIT(MAX3421_HI_SUSDN_BIT))
                pr_info("%s: SUSDN\n", __func__);

        chg = (old_port_status ^ max3421_hcd->port_status);
        max3421_hcd->port_status |= chg << 16;

        spin_unlock_irqrestore(&max3421_hcd->lock, flags);

#ifdef DEBUG
        {
                static unsigned long last_time;
                char sbuf[16 * 16], *dp, *end;
                int i;

                if (time_after(jiffies, last_time + 5*HZ)) {
                        dp = sbuf;
                        end = sbuf + sizeof(sbuf);
                        *dp = '\0';
                        for (i = 0; i < 16; ++i) {
                                int ret = scnprintf(dp, end - dp, " %lu",
                                                    max3421_hcd->err_stat[i]);
                                if (ret == end - dp - 1)
                                        break;  /* error or buffer full */
                                dp += ret;
                        }
                        pr_info("%s: hrsl_stats %s\n", __func__, sbuf);
                        memset(max3421_hcd->err_stat, 0,
                               sizeof(max3421_hcd->err_stat));
                        last_time = jiffies;

                        dump_eps(hcd);
                }
        }
#endif
        return 1;
}

static int
max3421_reset_hcd(struct usb_hcd *hcd)
{
        struct spi_device *spi = to_spi_device(hcd->self.controller);
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        int timeout;

        /* perform a chip reset and wait for OSCIRQ signal to appear: */
        spi_wr8(hcd, MAX3421_REG_USBCTL, BIT(MAX3421_USBCTL_CHIPRES_BIT));
        /* clear reset: */
        spi_wr8(hcd, MAX3421_REG_USBCTL, 0);
        timeout = 1000;
        while (1) {
                if (spi_rd8(hcd, MAX3421_REG_USBIRQ)
                    & BIT(MAX3421_USBIRQ_OSCOKIRQ_BIT))
                        break;
                if (--timeout < 0) {
                        dev_err(&spi->dev,
                                "timed out waiting for oscillator OK signal");
                        return 1;
                }
                cond_resched();
        }

        /*
         * Turn on host mode, automatic generation of SOF packets, and
         * enable pull-down registers on DM/DP:
         */
        max3421_hcd->mode = (BIT(MAX3421_MODE_HOST_BIT) |
                             BIT(MAX3421_MODE_SOFKAENAB_BIT) |
                             BIT(MAX3421_MODE_DMPULLDN_BIT) |
                             BIT(MAX3421_MODE_DPPULLDN_BIT));
        spi_wr8(hcd, MAX3421_REG_MODE, max3421_hcd->mode);

        /* reset frame-number: */
        max3421_hcd->frame_number = USB_MAX_FRAME_NUMBER;
        spi_wr8(hcd, MAX3421_REG_HCTL, BIT(MAX3421_HCTL_FRMRST_BIT));

        /* sample the state of the D+ and D- lines */
        spi_wr8(hcd, MAX3421_REG_HCTL, BIT(MAX3421_HCTL_SAMPLEBUS_BIT));
        max3421_detect_conn(hcd);

        /* enable frame, connection-detected, and bus-event interrupts: */
        max3421_hcd->hien = (BIT(MAX3421_HI_FRAME_BIT) |
                             BIT(MAX3421_HI_CONDET_BIT) |
                             BIT(MAX3421_HI_BUSEVENT_BIT));
        spi_wr8(hcd, MAX3421_REG_HIEN, max3421_hcd->hien);

        /* enable interrupts: */
        spi_wr8(hcd, MAX3421_REG_CPUCTL, BIT(MAX3421_CPUCTL_IE_BIT));
        return 1;
}

static int
max3421_urb_done(struct usb_hcd *hcd)
{
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        unsigned long flags;
        struct urb *urb;
        int status;

        status = max3421_hcd->urb_done;
        max3421_hcd->urb_done = 0;
        if (status > 0)
                status = 0;
        urb = max3421_hcd->curr_urb;
        if (urb) {
                /* save the old end-points toggles: */
                u8 hrsl = spi_rd8(hcd, MAX3421_REG_HRSL);
                int rcvtog = (hrsl >> MAX3421_HRSL_RCVTOGRD_BIT) & 1;
                int sndtog = (hrsl >> MAX3421_HRSL_SNDTOGRD_BIT) & 1;
                int epnum = usb_endpoint_num(&urb->ep->desc);

                /* no locking: HCD (i.e., we) own toggles, don't we? */
                usb_settoggle(urb->dev, epnum, 0, rcvtog);
                usb_settoggle(urb->dev, epnum, 1, sndtog);

                max3421_hcd->curr_urb = NULL;
                spin_lock_irqsave(&max3421_hcd->lock, flags);
                usb_hcd_unlink_urb_from_ep(hcd, urb);
                spin_unlock_irqrestore(&max3421_hcd->lock, flags);

                /* must be called without the HCD spinlock: */
                usb_hcd_giveback_urb(hcd, urb, status);
        }
        return 1;
}

static int
max3421_spi_thread(void *dev_id)
{
        struct usb_hcd *hcd = dev_id;
        struct spi_device *spi = to_spi_device(hcd->self.controller);
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        int i, i_worked = 1;

        /* set full-duplex SPI mode, low-active interrupt pin: */
        spi_wr8(hcd, MAX3421_REG_PINCTL,
                (BIT(MAX3421_PINCTL_FDUPSPI_BIT) |      /* full-duplex */
                 BIT(MAX3421_PINCTL_INTLEVEL_BIT)));    /* low-active irq */

        while (!kthread_should_stop()) {
                max3421_hcd->rev = spi_rd8(hcd, MAX3421_REG_REVISION);
                if (max3421_hcd->rev == 0x12 || max3421_hcd->rev == 0x13)
                        break;
                dev_err(&spi->dev, "bad rev 0x%02x", max3421_hcd->rev);
                msleep(10000);
        }
        dev_info(&spi->dev, "rev 0x%x, SPI clk %dHz, bpw %u, irq %d\n",
                 max3421_hcd->rev, spi->max_speed_hz, spi->bits_per_word,
                 spi->irq);

        while (!kthread_should_stop()) {
                if (!i_worked) {
                        /*
                         * We'll be waiting for wakeups from the hard
                         * interrupt handler, so now is a good time to
                         * sync our hien with the chip:
                         */
                        spi_wr8(hcd, MAX3421_REG_HIEN, max3421_hcd->hien);

                        set_current_state(TASK_INTERRUPTIBLE);
                        if (test_and_clear_bit(ENABLE_IRQ, &max3421_hcd->todo))
                                enable_irq(spi->irq);
                        schedule();
                        __set_current_state(TASK_RUNNING);
                }

                i_worked = 0;

                if (max3421_hcd->urb_done)
                        i_worked |= max3421_urb_done(hcd);
                else if (max3421_handle_irqs(hcd))
                        i_worked = 1;
                else if (!max3421_hcd->curr_urb)
                        i_worked |= max3421_select_and_start_urb(hcd);

                if (test_and_clear_bit(RESET_HCD, &max3421_hcd->todo))
                        /* reset the HCD: */
                        i_worked |= max3421_reset_hcd(hcd);
                if (test_and_clear_bit(RESET_PORT, &max3421_hcd->todo)) {
                        /* perform a USB bus reset: */
                        spi_wr8(hcd, MAX3421_REG_HCTL,
                                BIT(MAX3421_HCTL_BUSRST_BIT));
                        i_worked = 1;
                }
                if (test_and_clear_bit(CHECK_UNLINK, &max3421_hcd->todo))
                        i_worked |= max3421_check_unlink(hcd);
                if (test_and_clear_bit(IOPIN_UPDATE, &max3421_hcd->todo)) {
                        /*
                         * IOPINS1/IOPINS2 do not auto-increment, so we can't
                         * use spi_wr_buf().
                         */
                        for (i = 0; i < ARRAY_SIZE(max3421_hcd->iopins); ++i) {
                                u8 val = spi_rd8(hcd, MAX3421_REG_IOPINS1 + i);

                                val = ((val & 0xf0) |
                                       (max3421_hcd->iopins[i] & 0x0f));
                                spi_wr8(hcd, MAX3421_REG_IOPINS1 + i, val);
                                max3421_hcd->iopins[i] = val;
                        }
                        i_worked = 1;
                }
        }
        set_current_state(TASK_RUNNING);
        dev_info(&spi->dev, "SPI thread exiting");
        return 0;
}

static int
max3421_reset_port(struct usb_hcd *hcd)
{
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);

        max3421_hcd->port_status &= ~(USB_PORT_STAT_ENABLE |
                                      USB_PORT_STAT_LOW_SPEED);
        max3421_hcd->port_status |= USB_PORT_STAT_RESET;
        set_bit(RESET_PORT, &max3421_hcd->todo);
        wake_up_process(max3421_hcd->spi_thread);
        return 0;
}

static int
max3421_reset(struct usb_hcd *hcd)
{
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);

        hcd->self.sg_tablesize = 0;
        hcd->speed = HCD_USB2;
        hcd->self.root_hub->speed = USB_SPEED_FULL;
        set_bit(RESET_HCD, &max3421_hcd->todo);
        wake_up_process(max3421_hcd->spi_thread);
        return 0;
}

static int
max3421_start(struct usb_hcd *hcd)
{
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);

        spin_lock_init(&max3421_hcd->lock);
        max3421_hcd->rh_state = MAX3421_RH_RUNNING;

        INIT_LIST_HEAD(&max3421_hcd->ep_list);

        hcd->power_budget = POWER_BUDGET;
        hcd->state = HC_STATE_RUNNING;
        hcd->uses_new_polling = 1;
        return 0;
}

static void
max3421_stop(struct usb_hcd *hcd)
{
}

static int
max3421_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flags)
{
        struct spi_device *spi = to_spi_device(hcd->self.controller);
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        struct max3421_ep *max3421_ep;
        unsigned long flags;
        int retval;

        switch (usb_pipetype(urb->pipe)) {
        case PIPE_INTERRUPT:
        case PIPE_ISOCHRONOUS:
                if (urb->interval < 0) {
                        dev_err(&spi->dev,
                          "%s: interval=%d for intr-/iso-pipe; expected > 0\n",
                                __func__, urb->interval);
                        return -EINVAL;
                }
                break;
        default:
                break;
        }

        spin_lock_irqsave(&max3421_hcd->lock, flags);

        max3421_ep = urb->ep->hcpriv;
        if (!max3421_ep) {
                /* gets freed in max3421_endpoint_disable: */
                max3421_ep = kzalloc_obj(struct max3421_ep, GFP_ATOMIC);
                if (!max3421_ep) {
                        retval = -ENOMEM;
                        goto out;
                }
                max3421_ep->ep = urb->ep;
                max3421_ep->last_active = max3421_hcd->frame_number;
                urb->ep->hcpriv = max3421_ep;

                list_add_tail(&max3421_ep->ep_list, &max3421_hcd->ep_list);
        }

        retval = usb_hcd_link_urb_to_ep(hcd, urb);
        if (retval == 0) {
                /* Since we added to the queue, restart scheduling: */
                max3421_hcd->sched_pass = SCHED_PASS_PERIODIC;
                wake_up_process(max3421_hcd->spi_thread);
        }

out:
        spin_unlock_irqrestore(&max3421_hcd->lock, flags);
        return retval;
}

static int
max3421_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status)
{
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        unsigned long flags;
        int retval;

        spin_lock_irqsave(&max3421_hcd->lock, flags);

        /*
         * This will set urb->unlinked which in turn causes the entry
         * to be dropped at the next opportunity.
         */
        retval = usb_hcd_check_unlink_urb(hcd, urb, status);
        if (retval == 0) {
                set_bit(CHECK_UNLINK, &max3421_hcd->todo);
                wake_up_process(max3421_hcd->spi_thread);
        }
        spin_unlock_irqrestore(&max3421_hcd->lock, flags);
        return retval;
}

static void
max3421_endpoint_disable(struct usb_hcd *hcd, struct usb_host_endpoint *ep)
{
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        unsigned long flags;

        spin_lock_irqsave(&max3421_hcd->lock, flags);

        if (ep->hcpriv) {
                struct max3421_ep *max3421_ep = ep->hcpriv;

                /* remove myself from the ep_list: */
                if (!list_empty(&max3421_ep->ep_list))
                        list_del(&max3421_ep->ep_list);
                kfree(max3421_ep);
                ep->hcpriv = NULL;
        }

        spin_unlock_irqrestore(&max3421_hcd->lock, flags);
}

static int
max3421_get_frame_number(struct usb_hcd *hcd)
{
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        return max3421_hcd->frame_number;
}

/*
 * Should return a non-zero value when any port is undergoing a resume
 * transition while the root hub is suspended.
 */
static int
max3421_hub_status_data(struct usb_hcd *hcd, char *buf)
{
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        unsigned long flags;
        int retval = 0;

        spin_lock_irqsave(&max3421_hcd->lock, flags);
        if (!HCD_HW_ACCESSIBLE(hcd))
                goto done;

        *buf = 0;
        if ((max3421_hcd->port_status & PORT_C_MASK) != 0) {
                *buf = (1 << 1); /* a hub over-current condition exists */
                dev_dbg(hcd->self.controller,
                        "port status 0x%08x has changes\n",
                        max3421_hcd->port_status);
                retval = 1;
                if (max3421_hcd->rh_state == MAX3421_RH_SUSPENDED)
                        usb_hcd_resume_root_hub(hcd);
        }
done:
        spin_unlock_irqrestore(&max3421_hcd->lock, flags);
        return retval;
}

static inline void
hub_descriptor(struct usb_hub_descriptor *desc)
{
        memset(desc, 0, sizeof(*desc));
        /*
         * See Table 11-13: Hub Descriptor in USB 2.0 spec.
         */
        desc->bDescriptorType = USB_DT_HUB; /* hub descriptor */
        desc->bDescLength = 9;
        desc->wHubCharacteristics = cpu_to_le16(HUB_CHAR_INDV_PORT_LPSM |
                                                HUB_CHAR_COMMON_OCPM);
        desc->bNbrPorts = 1;
}

/*
 * Set the MAX3421E general-purpose output with number PIN_NUMBER to
 * VALUE (0 or 1).  PIN_NUMBER may be in the range from 1-8.  For
 * any other value, this function acts as a no-op.
 */
static void
max3421_gpout_set_value(struct usb_hcd *hcd, u8 pin_number, u8 value)
{
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        u8 mask, idx;

        --pin_number;
        if (pin_number >= MAX3421_GPOUT_COUNT)
                return;

        mask = 1u << (pin_number % 4);
        idx = pin_number / 4;

        if (value)
                max3421_hcd->iopins[idx] |=  mask;
        else
                max3421_hcd->iopins[idx] &= ~mask;
        set_bit(IOPIN_UPDATE, &max3421_hcd->todo);
        wake_up_process(max3421_hcd->spi_thread);
}

static int
max3421_hub_control(struct usb_hcd *hcd, u16 type_req, u16 value, u16 index,
                    char *buf, u16 length)
{
        struct spi_device *spi = to_spi_device(hcd->self.controller);
        struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
        struct max3421_hcd_platform_data *pdata;
        unsigned long flags;
        int retval = 0;

        pdata = spi->dev.platform_data;

        spin_lock_irqsave(&max3421_hcd->lock, flags);

        switch (type_req) {
        case ClearHubFeature:
                break;
        case ClearPortFeature:
                switch (value) {
                case USB_PORT_FEAT_SUSPEND:
                        break;
                case USB_PORT_FEAT_POWER:
                        dev_dbg(hcd->self.controller, "power-off\n");
                        max3421_gpout_set_value(hcd, pdata->vbus_gpout,
                                                !pdata->vbus_active_level);
                        fallthrough;
                default:
                        max3421_hcd->port_status &= ~(1 << value);
                }
                break;
        case GetHubDescriptor:
                hub_descriptor((struct usb_hub_descriptor *) buf);
                break;

        case DeviceRequest | USB_REQ_GET_DESCRIPTOR:
        case GetPortErrorCount:
        case SetHubDepth:
                /* USB3 only */
                goto error;

        case GetHubStatus:
                *(__le32 *) buf = cpu_to_le32(0);
                break;

        case GetPortStatus:
                if (index != 1) {
                        retval = -EPIPE;
                        goto error;
                }
                ((__le16 *) buf)[0] = cpu_to_le16(max3421_hcd->port_status);
                ((__le16 *) buf)[1] =
                        cpu_to_le16(max3421_hcd->port_status >> 16);
                break;

        case SetHubFeature:
                retval = -EPIPE;
                break;

        case SetPortFeature:
                switch (value) {
                case USB_PORT_FEAT_LINK_STATE:
                case USB_PORT_FEAT_U1_TIMEOUT:
                case USB_PORT_FEAT_U2_TIMEOUT:
                case USB_PORT_FEAT_BH_PORT_RESET:
                        goto error;
                case USB_PORT_FEAT_SUSPEND:
                        if (max3421_hcd->active)
                                max3421_hcd->port_status |=
                                        USB_PORT_STAT_SUSPEND;
                        break;
                case USB_PORT_FEAT_POWER:
                        dev_dbg(hcd->self.controller, "power-on\n");
                        max3421_hcd->port_status |= USB_PORT_STAT_POWER;
                        max3421_gpout_set_value(hcd, pdata->vbus_gpout,
                                                pdata->vbus_active_level);
                        break;
                case USB_PORT_FEAT_RESET:
                        max3421_reset_port(hcd);
                        fallthrough;
                default:
                        if ((max3421_hcd->port_status & USB_PORT_STAT_POWER)
                            != 0)
                                max3421_hcd->port_status |= (1 << value);
                }
                break;

        default:
                dev_dbg(hcd->self.controller,
                        "hub control req%04x v%04x i%04x l%d\n",
                        type_req, value, index, length);
error:          /* "protocol stall" on error */
                retval = -EPIPE;
        }

        spin_unlock_irqrestore(&max3421_hcd->lock, flags);
        return retval;
}

static int
max3421_bus_suspend(struct usb_hcd *hcd)
{
        return -1;
}

static int
max3421_bus_resume(struct usb_hcd *hcd)
{
        return -1;
}

static const struct hc_driver max3421_hcd_desc = {
        .description =          "max3421",
        .product_desc =         DRIVER_DESC,
        .hcd_priv_size =        sizeof(struct max3421_hcd),
        .flags =                HCD_USB11,
        .reset =                max3421_reset,
        .start =                max3421_start,
        .stop =                 max3421_stop,
        .get_frame_number =     max3421_get_frame_number,
        .urb_enqueue =          max3421_urb_enqueue,
        .urb_dequeue =          max3421_urb_dequeue,
        .endpoint_disable =     max3421_endpoint_disable,
        .hub_status_data =      max3421_hub_status_data,
        .hub_control =          max3421_hub_control,
        .bus_suspend =          max3421_bus_suspend,
        .bus_resume =           max3421_bus_resume,
};

static int
max3421_of_vbus_en_pin(struct device *dev, struct max3421_hcd_platform_data *pdata)
{
        int retval;
        uint32_t value[2];

        if (!pdata)
                return -EINVAL;

        retval = of_property_read_u32_array(dev->of_node, "maxim,vbus-en-pin", value, 2);
        if (retval) {
                dev_err(dev, "device tree node property 'maxim,vbus-en-pin' is missing\n");
                return retval;
        }
        dev_info(dev, "property 'maxim,vbus-en-pin' value is <%d %d>\n", value[0], value[1]);

        pdata->vbus_gpout = value[0];
        pdata->vbus_active_level = value[1];

        return 0;
}

static int
max3421_probe(struct spi_device *spi)
{
        struct device *dev = &spi->dev;
        struct max3421_hcd *max3421_hcd;
        struct usb_hcd *hcd = NULL;
        struct max3421_hcd_platform_data *pdata = NULL;
        int retval;

        if (spi_setup(spi) < 0) {
                dev_err(&spi->dev, "Unable to setup SPI bus");
                return -EFAULT;
        }

        if (!spi->irq) {
                dev_err(dev, "Failed to get SPI IRQ");
                return -EFAULT;
        }

        if (IS_ENABLED(CONFIG_OF) && dev->of_node) {
                pdata = devm_kzalloc(&spi->dev, sizeof(*pdata), GFP_KERNEL);
                if (!pdata) {
                        retval = -ENOMEM;
                        goto error;
                }
                retval = max3421_of_vbus_en_pin(dev, pdata);
                if (retval)
                        goto error;

                spi->dev.platform_data = pdata;
        }

        pdata = spi->dev.platform_data;
        if (!pdata) {
                dev_err(&spi->dev, "driver configuration data is not provided\n");
                retval = -EFAULT;
                goto error;
        }
        if (pdata->vbus_active_level > 1) {
                dev_err(&spi->dev, "vbus active level value %d is out of range (0/1)\n", pdata->vbus_active_level);
                retval = -EINVAL;
                goto error;
        }
        if (pdata->vbus_gpout < 1 || pdata->vbus_gpout > MAX3421_GPOUT_COUNT) {
                dev_err(&spi->dev, "vbus gpout value %d is out of range (1..8)\n", pdata->vbus_gpout);
                retval = -EINVAL;
                goto error;
        }

        retval = -ENOMEM;
        hcd = usb_create_hcd(&max3421_hcd_desc, &spi->dev,
                             dev_name(&spi->dev));
        if (!hcd) {
                dev_err(&spi->dev, "failed to create HCD structure\n");
                goto error;
        }
        set_bit(HCD_FLAG_POLL_RH, &hcd->flags);
        max3421_hcd = hcd_to_max3421(hcd);
        INIT_LIST_HEAD(&max3421_hcd->ep_list);
        spi_set_drvdata(spi, max3421_hcd);

        max3421_hcd->tx = kmalloc_obj(*max3421_hcd->tx);
        if (!max3421_hcd->tx)
                goto error;
        max3421_hcd->rx = kmalloc_obj(*max3421_hcd->rx);
        if (!max3421_hcd->rx)
                goto error;

        max3421_hcd->spi_thread = kthread_run(max3421_spi_thread, hcd,
                                              "max3421_spi_thread");
        if (max3421_hcd->spi_thread == ERR_PTR(-ENOMEM)) {
                dev_err(&spi->dev,
                        "failed to create SPI thread (out of memory)\n");
                goto error;
        }

        retval = usb_add_hcd(hcd, 0, 0);
        if (retval) {
                dev_err(&spi->dev, "failed to add HCD\n");
                goto error;
        }

        retval = request_irq(spi->irq, max3421_irq_handler,
                             IRQF_TRIGGER_LOW, "max3421", hcd);
        if (retval < 0) {
                dev_err(&spi->dev, "failed to request irq %d\n", spi->irq);
                goto error;
        }
        return 0;

error:
        if (IS_ENABLED(CONFIG_OF) && dev->of_node && pdata) {
                devm_kfree(&spi->dev, pdata);
                spi->dev.platform_data = NULL;
        }

        if (hcd) {
                kfree(max3421_hcd->tx);
                kfree(max3421_hcd->rx);
                if (!IS_ERR_OR_NULL(max3421_hcd->spi_thread))
                        kthread_stop(max3421_hcd->spi_thread);
                usb_put_hcd(hcd);
        }
        return retval;
}

static void
max3421_remove(struct spi_device *spi)
{
        struct max3421_hcd *max3421_hcd;
        struct usb_hcd *hcd;
        unsigned long flags;

        max3421_hcd = spi_get_drvdata(spi);
        hcd = max3421_to_hcd(max3421_hcd);

        usb_remove_hcd(hcd);

        spin_lock_irqsave(&max3421_hcd->lock, flags);

        kthread_stop(max3421_hcd->spi_thread);

        spin_unlock_irqrestore(&max3421_hcd->lock, flags);

        free_irq(spi->irq, hcd);

        usb_put_hcd(hcd);
}

static const struct spi_device_id max3421_spi_ids[] = {
        { "max3421" },
        { },
};
MODULE_DEVICE_TABLE(spi, max3421_spi_ids);

static const struct of_device_id max3421_of_match_table[] = {
        { .compatible = "maxim,max3421", },
        {},
};
MODULE_DEVICE_TABLE(of, max3421_of_match_table);

static struct spi_driver max3421_driver = {
        .probe          = max3421_probe,
        .remove         = max3421_remove,
        .id_table       = max3421_spi_ids,
        .driver         = {
                .name   = "max3421-hcd",
                .of_match_table = max3421_of_match_table,
        },
};

module_spi_driver(max3421_driver);

MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_AUTHOR("David Mosberger <davidm@egauge.net>");
MODULE_LICENSE("GPL");