/*
 * The MIT License (MIT)
 *
 * Copyright (c) 2018 Scott Shawcroft, 2019 William D. Jones for Adafruit Industries
 * Copyright (c) 2019 Ha Thach (tinyusb.org)
 * Additions Copyright (c) 2020, Espressif Systems (Shanghai) Co. Ltd.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * This file is part of the TinyUSB stack.
 */

#include "tusb_option.h"

#if (((CFG_TUSB_MCU == OPT_MCU_ESP32S2) ||  (CFG_TUSB_MCU == OPT_MCU_ESP32S3)) && TUSB_OPT_DEVICE_ENABLED)

// Espressif
#include "driver/periph_ctrl.h"
#include "freertos/xtensa_api.h"
#include "esp_intr_alloc.h"
#include "esp_log.h"
#include "driver/gpio.h"
#include "soc/dport_reg.h"
#include "soc/gpio_sig_map.h"
#include "soc/usb_periph.h"

#include "device/dcd.h"

// Since TinyUSB doesn't use SOF for now, and this interrupt too often (1ms interval)
// We disable SOF for now until needed later on
#define USE_SOF     0

// Max number of bi-directional endpoints including EP0
// Note: ESP32S2 specs say there are only up to 5 IN active endpoints include EP0
// We should probably prohibit enabling Endpoint IN > 4 (not done yet)
#define EP_MAX            USB_OUT_EP_NUM

// FIFO size in bytes
#define EP_FIFO_SIZE      1024

// Max number of IN EP FIFOs
#define EP_FIFO_NUM 5

typedef struct {
    uint8_t *buffer;
    // tu_fifo_t * ff; // TODO support dcd_edpt_xfer_fifo API
    uint16_t total_len;
    uint16_t queued_len;
    uint16_t max_size;
    bool short_packet;
} xfer_ctl_t;

static const char *TAG = "TUSB:DCD";
static intr_handle_t usb_ih;


static uint32_t _setup_packet[2];

#define XFER_CTL_BASE(_ep, _dir) &xfer_status[_ep][_dir]
static xfer_ctl_t xfer_status[EP_MAX][2];

// Keep count of how many FIFOs are in use
static uint8_t _allocated_fifos = 1; //FIFO0 is always in use

// Will either return an unused FIFO number, or 0 if all are used.
static uint8_t get_free_fifo(void)
{
  if (_allocated_fifos < EP_FIFO_NUM) return _allocated_fifos++;
  return 0;
}

// Setup the control endpoint 0.
static void bus_reset(void)
{
  for (int ep_num = 0; ep_num < USB_OUT_EP_NUM; ep_num++) {
    USB0.out_ep_reg[ep_num].doepctl |= USB_DO_SNAK0_M; // DOEPCTL0_SNAK
  }

  USB0.dcfg &= ~USB_DEVADDR_M; // reset address

  USB0.daintmsk |= USB_OUTEPMSK0_M | USB_INEPMSK0_M;
  USB0.doepmsk |= USB_SETUPMSK_M | USB_XFERCOMPLMSK;
  USB0.diepmsk |= USB_TIMEOUTMSK_M | USB_DI_XFERCOMPLMSK_M /*| USB_INTKNTXFEMPMSK_M*/;

  // "USB Data FIFOs" section in reference manual
  // Peripheral FIFO architecture
  //
  // --------------- 320 or 1024 ( 1280 or 4096 bytes )
  // | IN FIFO MAX |
  // ---------------
  // |    ...      |
  // --------------- y + x + 16 + GRXFSIZ
  // | IN FIFO 2   |
  // --------------- x + 16 + GRXFSIZ
  // | IN FIFO 1   |
  // --------------- 16 + GRXFSIZ
  // | IN FIFO 0   |
  // --------------- GRXFSIZ
  // | OUT FIFO    |
  // | ( Shared )  |
  // --------------- 0
  //
  // According to "FIFO RAM allocation" section in RM, FIFO RAM are allocated as follows (each word 32-bits):
  // - Each EP IN needs at least max packet size, 16 words is sufficient for EP0 IN
  //
  // - All EP OUT shared a unique OUT FIFO which uses
  //   * 10 locations in hardware for setup packets + setup control words (up to 3 setup packets).
  //   * 2 locations for OUT endpoint control words.
  //   * 16 for largest packet size of 64 bytes. ( TODO Highspeed is 512 bytes)
  //   * 1 location for global NAK (not required/used here).
  //   * It is recommended to allocate 2 times the largest packet size, therefore
  //   Recommended value = 10 + 1 + 2 x (16+2) = 47 --> Let's make it 52
  USB0.grstctl |= 0x10 << USB_TXFNUM_S; // fifo 0x10,
  USB0.grstctl |= USB_TXFFLSH_M;        // Flush fifo
  USB0.grxfsiz = 52;

  // Control IN uses FIFO 0 with 64 bytes ( 16 32-bit word )
  USB0.gnptxfsiz = (16 << USB_NPTXFDEP_S) | (USB0.grxfsiz & 0x0000ffffUL);

  // Ready to receive SETUP packet
  USB0.out_ep_reg[0].doeptsiz |= USB_SUPCNT0_M;

  USB0.gintmsk |= USB_IEPINTMSK_M | USB_OEPINTMSK_M;
}

static void enum_done_processing(void)
{
  ESP_EARLY_LOGV(TAG, "dcd_int_handler - Speed enumeration done! Sending DCD_EVENT_BUS_RESET then");
  // On current silicon on the Full Speed core, speed is fixed to Full Speed.
  // However, keep for debugging and in case Low Speed is ever supported.
  uint32_t enum_spd = (USB0.dsts >> USB_ENUMSPD_S) & (USB_ENUMSPD_V);

  // Maximum packet size for EP 0 is set for both directions by writing DIEPCTL
  if (enum_spd == 0x03) { // Full-Speed (PHY on 48 MHz)
    USB0.in_ep_reg[0].diepctl &= ~USB_D_MPS0_V;    // 64 bytes
    USB0.in_ep_reg[0].diepctl &= ~USB_D_STALL0_M; // clear Stall
    xfer_status[0][TUSB_DIR_OUT].max_size = 64;
    xfer_status[0][TUSB_DIR_IN].max_size = 64;
  } else {
    USB0.in_ep_reg[0].diepctl |= USB_D_MPS0_V;     // 8 bytes
    USB0.in_ep_reg[0].diepctl &= ~USB_D_STALL0_M; // clear Stall
    xfer_status[0][TUSB_DIR_OUT].max_size = 8;
    xfer_status[0][TUSB_DIR_IN].max_size = 8;
  }
}


/*------------------------------------------------------------------*/
/* Controller API
 *------------------------------------------------------------------*/
void dcd_init(uint8_t rhport)
{
  ESP_LOGV(TAG, "DCD init - Start");

  // A. Disconnect
  ESP_LOGV(TAG, "DCD init - Soft DISCONNECT and Setting up");
  USB0.dctl |= USB_SFTDISCON_M; // Soft disconnect

  // B. Programming DCFG
  /* If USB host misbehaves during status portion of control xfer
    (non zero-length packet), send STALL back and discard. Full speed. */
  USB0.dcfg |= USB_NZSTSOUTHSHK_M | // NonZero .... STALL
      (3 << 0);            // dev speed: fullspeed 1.1 on 48 mhz  // TODO no value in usb_reg.h (IDF-1476)

  USB0.gahbcfg |= USB_NPTXFEMPLVL_M | USB_GLBLLNTRMSK_M; // Global interruptions ON
  USB0.gusbcfg |= USB_FORCEDEVMODE_M;                    // force devmode
  USB0.gotgctl &= ~(USB_BVALIDOVVAL_M | USB_BVALIDOVEN_M | USB_VBVALIDOVVAL_M); //no overrides

  // C. Setting SNAKs, then connect
  for (int n = 0; n < USB_OUT_EP_NUM; n++) {
    USB0.out_ep_reg[n].doepctl |= USB_DO_SNAK0_M; // DOEPCTL0_SNAK
  }

  // D. Interruption masking
  USB0.gintmsk = 0;   //mask all
  USB0.gotgint = ~0U; //clear OTG ints
  USB0.gintsts = ~0U; //clear pending ints
  USB0.gintmsk = USB_OTGINTMSK_M   |
                 USB_MODEMISMSK_M  |
          #if USE_SOF
                 USB_SOFMSK_M      |
          #endif
                 USB_RXFLVIMSK_M   |
                 USB_ERLYSUSPMSK_M |
                 USB_USBSUSPMSK_M  |
                 USB_USBRSTMSK_M   |
                 USB_ENUMDONEMSK_M |
                 USB_RESETDETMSK_M |
                 USB_DISCONNINTMSK_M; // host most only

  dcd_connect(rhport);
}

void dcd_set_address(uint8_t rhport, uint8_t dev_addr)
{
  (void)rhport;
  ESP_LOGV(TAG, "DCD init - Set address : %u", dev_addr);
  USB0.dcfg |= ((dev_addr & USB_DEVADDR_V) << USB_DEVADDR_S);
  // Response with status after changing device address
  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0);
}

void dcd_remote_wakeup(uint8_t rhport)
{
  (void)rhport;

  // TODO must manually clear this bit after 1-15 ms
  // USB0.DCTL |= USB_RMTWKUPSIG_M;
}

// connect by enabling internal pull-up resistor on D+/D-
void dcd_connect(uint8_t rhport)
{
  (void) rhport;
  USB0.dctl &= ~USB_SFTDISCON_M;
}

// disconnect by disabling internal pull-up resistor on D+/D-
void dcd_disconnect(uint8_t rhport)
{
  (void) rhport;
  USB0.dctl |= USB_SFTDISCON_M;
}

/*------------------------------------------------------------------*/
/* DCD Endpoint port
 *------------------------------------------------------------------*/

bool dcd_edpt_open(uint8_t rhport, tusb_desc_endpoint_t const *desc_edpt)
{
  ESP_LOGV(TAG, "DCD endpoint opened");
  (void)rhport;

  usb_out_endpoint_t *out_ep = &(USB0.out_ep_reg[0]);
  usb_in_endpoint_t *in_ep = &(USB0.in_ep_reg[0]);

  uint8_t const epnum = tu_edpt_number(desc_edpt->bEndpointAddress);
  uint8_t const dir = tu_edpt_dir(desc_edpt->bEndpointAddress);

  TU_ASSERT(desc_edpt->wMaxPacketSize.size <= 64);
  TU_ASSERT(epnum < EP_MAX);

  xfer_ctl_t *xfer = XFER_CTL_BASE(epnum, dir);
  xfer->max_size = desc_edpt->wMaxPacketSize.size;

  if (dir == TUSB_DIR_OUT) {
    out_ep[epnum].doepctl |= USB_USBACTEP0_M |
                             desc_edpt->bmAttributes.xfer << USB_EPTYPE0_S |
                             desc_edpt->wMaxPacketSize.size << USB_MPS0_S;
    USB0.daintmsk |= (1 << (16 + epnum));
  } else {
    // "USB Data FIFOs" section in reference manual
    // Peripheral FIFO architecture
    //
    // --------------- 320 or 1024 ( 1280 or 4096 bytes )
    // | IN FIFO MAX |
    // ---------------
    // |    ...      |
    // --------------- y + x + 16 + GRXFSIZ
    // | IN FIFO 2   |
    // --------------- x + 16 + GRXFSIZ
    // | IN FIFO 1   |
    // --------------- 16 + GRXFSIZ
    // | IN FIFO 0   |
    // --------------- GRXFSIZ
    // | OUT FIFO    |
    // | ( Shared )  |
    // --------------- 0
    //
    // Since OUT FIFO = GRXFSIZ, FIFO 0 = 16, for simplicity, we equally allocated for the rest of endpoints
    // - Size  : (FIFO_SIZE/4 - GRXFSIZ - 16) / (EP_MAX-1)
    // - Offset: GRXFSIZ + 16 + Size*(epnum-1)
    // - IN EP 1 gets FIFO 1, IN EP "n" gets FIFO "n".

    uint8_t fifo_num = get_free_fifo();
    TU_ASSERT(fifo_num != 0);

    in_ep[epnum].diepctl &= ~(USB_D_TXFNUM1_M | USB_D_EPTYPE1_M | USB_DI_SETD0PID1 | USB_D_MPS1_M);
    in_ep[epnum].diepctl |= USB_D_USBACTEP1_M |
                            fifo_num << USB_D_TXFNUM1_S |
                            desc_edpt->bmAttributes.xfer << USB_D_EPTYPE1_S |
                            (desc_edpt->bmAttributes.xfer != TUSB_XFER_ISOCHRONOUS ? (1 << USB_DI_SETD0PID1_S) : 0) |
                            desc_edpt->wMaxPacketSize.size << 0;

    USB0.daintmsk |= (1 << (0 + epnum));

    // Both TXFD and TXSA are in unit of 32-bit words.
    // IN FIFO 0 was configured during enumeration, hence the "+ 16".
    uint16_t const allocated_size = (USB0.grxfsiz & 0x0000ffff) + 16;
    uint16_t const fifo_size = (EP_FIFO_SIZE/4 - allocated_size) / (EP_FIFO_NUM-1);
    uint32_t const fifo_offset = allocated_size + fifo_size*(fifo_num-1);

    // DIEPTXF starts at FIFO #1.
    USB0.dieptxf[epnum - 1] = (fifo_size << USB_NPTXFDEP_S) | fifo_offset;
  }
  return true;
}

bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t *buffer, uint16_t total_bytes)
{
  (void)rhport;

  uint8_t const epnum = tu_edpt_number(ep_addr);
  uint8_t const dir   = tu_edpt_dir(ep_addr);

  xfer_ctl_t * xfer = XFER_CTL_BASE(epnum, dir);
  xfer->buffer       = buffer;
  // xfer->ff           = NULL; // TODO support dcd_edpt_xfer_fifo API
  xfer->total_len    = total_bytes;
  xfer->queued_len   = 0;
  xfer->short_packet = false;

  uint16_t num_packets = (total_bytes / xfer->max_size);
  uint8_t short_packet_size = total_bytes % xfer->max_size;

  // Zero-size packet is special case.
  if (short_packet_size > 0 || (total_bytes == 0)) {
    num_packets++;
  }

  ESP_LOGV(TAG, "Transfer <-> EP%i, %s, pkgs: %i, bytes: %i",
           epnum, ((dir == TUSB_DIR_IN) ? "USB0.HOST (in)" : "HOST->DEV (out)"),
           num_packets, total_bytes);

  // IN and OUT endpoint xfers are interrupt-driven, we just schedule them
  // here.
  if (dir == TUSB_DIR_IN) {
    // A full IN transfer (multiple packets, possibly) triggers XFRC.
    USB0.in_ep_reg[epnum].dieptsiz = (num_packets << USB_D_PKTCNT0_S) | total_bytes;
    USB0.in_ep_reg[epnum].diepctl |= USB_D_EPENA1_M | USB_D_CNAK1_M; // Enable | CNAK

    // Enable fifo empty interrupt only if there are something to put in the fifo.
    if(total_bytes != 0) {
      USB0.dtknqr4_fifoemptymsk |= (1 << epnum);
    }
  } else {
    // Each complete packet for OUT xfers triggers XFRC.
    USB0.out_ep_reg[epnum].doeptsiz |= USB_PKTCNT0_M | ((xfer->max_size & USB_XFERSIZE0_V) << USB_XFERSIZE0_S);
    USB0.out_ep_reg[epnum].doepctl  |= USB_EPENA0_M | USB_CNAK0_M;
  }
  return true;
}

#if 0 // TODO support dcd_edpt_xfer_fifo API
bool dcd_edpt_xfer_fifo (uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes)
{
  (void)rhport;

  // USB buffers always work in bytes so to avoid unnecessary divisions we demand item_size = 1
  TU_ASSERT(ff->item_size == 1);

  uint8_t const epnum = tu_edpt_number(ep_addr);
  uint8_t const dir   = tu_edpt_dir(ep_addr);

  xfer_ctl_t * xfer = XFER_CTL_BASE(epnum, dir);
  xfer->buffer       = NULL;
  xfer->ff           = ff;
  xfer->total_len    = total_bytes;
  xfer->queued_len   = 0;
  xfer->short_packet = false;

  uint16_t num_packets = (total_bytes / xfer->max_size);
  uint8_t short_packet_size = total_bytes % xfer->max_size;

  // Zero-size packet is special case.
  if (short_packet_size > 0 || (total_bytes == 0)) {
    num_packets++;
  }

  ESP_LOGV(TAG, "Transfer <-> EP%i, %s, pkgs: %i, bytes: %i",
           epnum, ((dir == TUSB_DIR_IN) ? "USB0.HOST (in)" : "HOST->DEV (out)"),
           num_packets, total_bytes);

  // IN and OUT endpoint xfers are interrupt-driven, we just schedule them
  // here.
  if (dir == TUSB_DIR_IN) {
    // A full IN transfer (multiple packets, possibly) triggers XFRC.
    USB0.in_ep_reg[epnum].dieptsiz = (num_packets << USB_D_PKTCNT0_S) | total_bytes;
    USB0.in_ep_reg[epnum].diepctl |= USB_D_EPENA1_M | USB_D_CNAK1_M; // Enable | CNAK

    // Enable fifo empty interrupt only if there are something to put in the fifo.
    if(total_bytes != 0) {
      USB0.dtknqr4_fifoemptymsk |= (1 << epnum);
    }
  } else {
    // Each complete packet for OUT xfers triggers XFRC.
    USB0.out_ep_reg[epnum].doeptsiz |= USB_PKTCNT0_M | ((xfer->max_size & USB_XFERSIZE0_V) << USB_XFERSIZE0_S);
    USB0.out_ep_reg[epnum].doepctl  |= USB_EPENA0_M | USB_CNAK0_M;
  }
  return true;
}
#endif

void dcd_edpt_stall(uint8_t rhport, uint8_t ep_addr)
{
  (void)rhport;

  usb_out_endpoint_t *out_ep = &(USB0.out_ep_reg[0]);
  usb_in_endpoint_t *in_ep = &(USB0.in_ep_reg[0]);

  uint8_t const epnum = tu_edpt_number(ep_addr);
  uint8_t const dir = tu_edpt_dir(ep_addr);

  if (dir == TUSB_DIR_IN) {
    // Only disable currently enabled non-control endpoint
    if ((epnum == 0) || !(in_ep[epnum].diepctl & USB_D_EPENA1_M)) {
      in_ep[epnum].diepctl |= (USB_DI_SNAK1_M | USB_D_STALL1_M);
    } else {
      // Stop transmitting packets and NAK IN xfers.
      in_ep[epnum].diepctl |= USB_DI_SNAK1_M;
      while ((in_ep[epnum].diepint & USB_DI_SNAK1_M) == 0) ;

      // Disable the endpoint. Note that both SNAK and STALL are set here.
      in_ep[epnum].diepctl |= (USB_DI_SNAK1_M | USB_D_STALL1_M | USB_D_EPDIS1_M);
      while ((in_ep[epnum].diepint & USB_D_EPDISBLD0_M) == 0) ;
      in_ep[epnum].diepint = USB_D_EPDISBLD0_M;
    }

    // Flush the FIFO, and wait until we have confirmed it cleared.
    uint8_t const fifo_num = ((in_ep[epnum].diepctl >> USB_D_TXFNUM1_S) & USB_D_TXFNUM1_V);
    USB0.grstctl |= (fifo_num << USB_TXFNUM_S);
    USB0.grstctl |= USB_TXFFLSH_M;
    while ((USB0.grstctl & USB_TXFFLSH_M) != 0) ;
  } else {
    // Only disable currently enabled non-control endpoint
    if ((epnum == 0) || !(out_ep[epnum].doepctl & USB_EPENA0_M)) {
      out_ep[epnum].doepctl |= USB_STALL0_M;
    } else {
      // Asserting GONAK is required to STALL an OUT endpoint.
      // Simpler to use polling here, we don't use the "B"OUTNAKEFF interrupt
      // anyway, and it can't be cleared by user code. If this while loop never
      // finishes, we have bigger problems than just the stack.
      USB0.dctl |= USB_SGOUTNAK_M;
      while ((USB0.gintsts & USB_GOUTNAKEFF_M) == 0) ;

      // Ditto here- disable the endpoint. Note that only STALL and not SNAK
      // is set here.
      out_ep[epnum].doepctl |= (USB_STALL0_M | USB_EPDIS0_M);
      while ((out_ep[epnum].doepint & USB_EPDISBLD0_M) == 0) ;
      out_ep[epnum].doepint = USB_EPDISBLD0_M;

      // Allow other OUT endpoints to keep receiving.
      USB0.dctl |= USB_CGOUTNAK_M;
    }
  }
}

void dcd_edpt_clear_stall(uint8_t rhport, uint8_t ep_addr)
{
  (void)rhport;

  usb_out_endpoint_t *out_ep = &(USB0.out_ep_reg[0]);
  usb_in_endpoint_t *in_ep = &(USB0.in_ep_reg[0]);

  uint8_t const epnum = tu_edpt_number(ep_addr);
  uint8_t const dir = tu_edpt_dir(ep_addr);

  if (dir == TUSB_DIR_IN) {
    in_ep[epnum].diepctl &= ~USB_D_STALL1_M;

    uint8_t eptype = (in_ep[epnum].diepctl & USB_D_EPTYPE1_M) >> USB_D_EPTYPE1_S;
    // Required by USB spec to reset DATA toggle bit to DATA0 on interrupt
    // and bulk endpoints.
    if (eptype == 2 || eptype == 3) {
      in_ep[epnum].diepctl |= USB_DI_SETD0PID1_M;
    }
  } else {
    out_ep[epnum].doepctl &= ~USB_STALL1_M;

    uint8_t eptype = (out_ep[epnum].doepctl & USB_EPTYPE1_M) >> USB_EPTYPE1_S;
    // Required by USB spec to reset DATA toggle bit to DATA0 on interrupt
    // and bulk endpoints.
    if (eptype == 2 || eptype == 3) {
      out_ep[epnum].doepctl |= USB_DO_SETD0PID1_M;
    }
  }
}

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

static void receive_packet(xfer_ctl_t *xfer, /* usb_out_endpoint_t * out_ep, */ uint16_t xfer_size)
{
  ESP_EARLY_LOGV(TAG, "USB - receive_packet");
  volatile uint32_t *rx_fifo = USB0.fifo[0];

  // See above TODO
  // uint16_t remaining = (out_ep->DOEPTSIZ & UsbDOEPTSIZ_XFRSIZ_Msk) >> UsbDOEPTSIZ_XFRSIZ_Pos;
  // xfer->queued_len = xfer->total_len - remaining;

  uint16_t remaining = xfer->total_len - xfer->queued_len;
  uint16_t to_recv_size;

  if (remaining <= xfer->max_size) {
    // Avoid buffer overflow.
    to_recv_size = (xfer_size > remaining) ? remaining : xfer_size;
  } else {
    // Room for full packet, choose recv_size based on what the microcontroller
    // claims.
    to_recv_size = (xfer_size > xfer->max_size) ? xfer->max_size : xfer_size;
  }

  // Common buffer read
#if 0 // TODO support dcd_edpt_xfer_fifo API
  if (xfer->ff)
  {
    // Ring buffer
    tu_fifo_write_n_const_addr_full_words(xfer->ff, (const void *) rx_fifo, to_recv_size);
  }
  else
#endif
  {
    uint8_t to_recv_rem = to_recv_size % 4;
    uint16_t to_recv_size_aligned = to_recv_size - to_recv_rem;

    // Do not assume xfer buffer is aligned.
    uint8_t *base = (xfer->buffer + xfer->queued_len);

    // This for loop always runs at least once- skip if less than 4 bytes
    // to collect.
    if (to_recv_size >= 4) {
      for (uint16_t i = 0; i < to_recv_size_aligned; i += 4) {
        uint32_t tmp = (*rx_fifo);
        base[i] = tmp & 0x000000FF;
        base[i + 1] = (tmp & 0x0000FF00) >> 8;
        base[i + 2] = (tmp & 0x00FF0000) >> 16;
        base[i + 3] = (tmp & 0xFF000000) >> 24;
      }
    }

    // Do not read invalid bytes from RX FIFO.
    if (to_recv_rem != 0) {
      uint32_t tmp = (*rx_fifo);
      uint8_t *last_32b_bound = base + to_recv_size_aligned;

      last_32b_bound[0] = tmp & 0x000000FF;
      if (to_recv_rem > 1) {
        last_32b_bound[1] = (tmp & 0x0000FF00) >> 8;
      }
      if (to_recv_rem > 2) {
        last_32b_bound[2] = (tmp & 0x00FF0000) >> 16;
      }
    }
  }

  xfer->queued_len += xfer_size;

  // Per USB spec, a short OUT packet (including length 0) is always
  // indicative of the end of a transfer (at least for ctl, bulk, int).
  xfer->short_packet = (xfer_size < xfer->max_size);
}

static void transmit_packet(xfer_ctl_t *xfer, volatile usb_in_endpoint_t *in_ep, uint8_t fifo_num)
{
  ESP_EARLY_LOGV(TAG, "USB - transmit_packet");
  volatile uint32_t *tx_fifo = USB0.fifo[fifo_num];

  uint16_t remaining = (in_ep->dieptsiz & 0x7FFFFU) >> USB_D_XFERSIZE0_S;
  xfer->queued_len = xfer->total_len - remaining;

  uint16_t to_xfer_size = (remaining > xfer->max_size) ? xfer->max_size : remaining;

#if 0 // TODO support dcd_edpt_xfer_fifo API
  if (xfer->ff)
  {
    tu_fifo_read_n_const_addr_full_words(xfer->ff, (void *) tx_fifo, to_xfer_size);
  }
  else
#endif
  {
    uint8_t to_xfer_rem = to_xfer_size % 4;
    uint16_t to_xfer_size_aligned = to_xfer_size - to_xfer_rem;

    // Buffer might not be aligned to 32b, so we need to force alignment
    // by copying to a temp var.
    uint8_t *base = (xfer->buffer + xfer->queued_len);

    // This for loop always runs at least once- skip if less than 4 bytes
    // to send off.
    if (to_xfer_size >= 4) {
      for (uint16_t i = 0; i < to_xfer_size_aligned; i += 4) {
        uint32_t tmp = base[i] | (base[i + 1] << 8) |
            (base[i + 2] << 16) | (base[i + 3] << 24);
        (*tx_fifo) = tmp;
      }
    }

    // Do not read beyond end of buffer if not divisible by 4.
    if (to_xfer_rem != 0) {
      uint32_t tmp = 0;
      uint8_t *last_32b_bound = base + to_xfer_size_aligned;

      tmp |= last_32b_bound[0];
      if (to_xfer_rem > 1) {
        tmp |= (last_32b_bound[1] << 8);
      }
      if (to_xfer_rem > 2) {
        tmp |= (last_32b_bound[2] << 16);
      }

      (*tx_fifo) = tmp;
    }
  }
}

static void read_rx_fifo(void)
{
  // Pop control word off FIFO (completed xfers will have 2 control words,
  // we only pop one ctl word each interrupt).
  uint32_t const ctl_word = USB0.grxstsp;
  uint8_t  const pktsts   = (ctl_word & USB_PKTSTS_M) >> USB_PKTSTS_S;
  uint8_t  const epnum    = (ctl_word & USB_CHNUM_M ) >> USB_CHNUM_S;
  uint16_t const bcnt     = (ctl_word & USB_BCNT_M  ) >> USB_BCNT_S;

  switch (pktsts) {
    case 0x01: // Global OUT NAK (Interrupt)
      ESP_EARLY_LOGV(TAG, "TUSB IRQ - RX type : Global OUT NAK");
      break;

    case 0x02: { // Out packet recvd
      ESP_EARLY_LOGV(TAG, "TUSB IRQ - RX type : Out packet");
      xfer_ctl_t *xfer = XFER_CTL_BASE(epnum, TUSB_DIR_OUT);
      receive_packet(xfer, bcnt);
    }
    break;

    case 0x03: // Out packet done (Interrupt)
      ESP_EARLY_LOGV(TAG, "TUSB IRQ - RX type : Out packet done");
      break;

    case 0x04: // Step 2: Setup transaction completed (Interrupt)
      // After this event, OEPINT interrupt will occur with SETUP bit set
      ESP_EARLY_LOGV(TAG, "TUSB IRQ - RX : Setup packet done");
      USB0.out_ep_reg[epnum].doeptsiz |= USB_SUPCNT0_M;
      break;

    case 0x06: { // Step1: Setup data packet received
      volatile uint32_t *rx_fifo = USB0.fifo[0];

      // We can receive up to three setup packets in succession, but
      // only the last one is valid. Therefore we just overwrite it
      _setup_packet[0] = (*rx_fifo);
      _setup_packet[1] = (*rx_fifo);

      ESP_EARLY_LOGV(TAG, "TUSB IRQ - RX : Setup packet : 0x%08x 0x%08x", _setup_packet[0], _setup_packet[1]);
    }
    break;

    default: // Invalid, do something here, like breakpoint?
      TU_BREAKPOINT();
      break;
  }
}

static void handle_epout_ints(void)
{
  // GINTSTS will be cleared with DAINT == 0
  // DAINT for a given EP clears when DOEPINTx is cleared.
  // DOEPINT will be cleared when DAINT's out bits are cleared.
  for (int n = 0; n < USB_OUT_EP_NUM; n++) {
    xfer_ctl_t *xfer = XFER_CTL_BASE(n, TUSB_DIR_OUT);

    if (USB0.daint & (1 << (16 + n))) {
      // SETUP packet Setup Phase done.
      if ((USB0.out_ep_reg[n].doepint & USB_SETUP0_M)) {
        USB0.out_ep_reg[n].doepint = USB_STUPPKTRCVD0_M | USB_SETUP0_M; // clear
        dcd_event_setup_received(0, (uint8_t *)&_setup_packet[0], true);
      }

      // OUT XFER complete (single packet).q
      if (USB0.out_ep_reg[n].doepint & USB_XFERCOMPL0_M) {

        ESP_EARLY_LOGV(TAG, "TUSB IRQ - EP OUT - XFER complete (single packet)");
        USB0.out_ep_reg[n].doepint = USB_XFERCOMPL0_M;

        // Transfer complete if short packet or total len is transferred
        if (xfer->short_packet || (xfer->queued_len == xfer->total_len)) {
          xfer->short_packet = false;
          dcd_event_xfer_complete(0, n, xfer->queued_len, XFER_RESULT_SUCCESS, true);
        } else {
          // Schedule another packet to be received.
          USB0.out_ep_reg[n].doeptsiz |= USB_PKTCNT0_M | ((xfer->max_size & USB_XFERSIZE0_V) << USB_XFERSIZE0_S);
          USB0.out_ep_reg[n].doepctl |= USB_EPENA0_M | USB_CNAK0_M;
        }
      }
    }
  }
}

static void handle_epin_ints(void)
{
  // GINTSTS will be cleared with DAINT == 0
  // DAINT for a given EP clears when DIEPINTx is cleared.
  // IEPINT will be cleared when DAINT's out bits are cleared.
  for (uint32_t n = 0; n < USB_IN_EP_NUM; n++) {
    xfer_ctl_t *xfer = &xfer_status[n][TUSB_DIR_IN];

    if (USB0.daint & (1 << (0 + n))) {
      ESP_EARLY_LOGV(TAG, "TUSB IRQ - EP IN %u", n);
      // IN XFER complete (entire xfer).
      if (USB0.in_ep_reg[n].diepint & USB_D_XFERCOMPL0_M) {
        ESP_EARLY_LOGV(TAG, "TUSB IRQ - IN XFER complete!");
        USB0.in_ep_reg[n].diepint = USB_D_XFERCOMPL0_M;
        dcd_event_xfer_complete(0, n | TUSB_DIR_IN_MASK, xfer->total_len, XFER_RESULT_SUCCESS, true);
      }

      // XFER FIFO empty
      if (USB0.in_ep_reg[n].diepint & USB_D_TXFEMP0_M) {
        ESP_EARLY_LOGV(TAG, "TUSB IRQ - IN XFER FIFO empty!");
        USB0.in_ep_reg[n].diepint = USB_D_TXFEMP0_M;
        transmit_packet(xfer, &USB0.in_ep_reg[n], n);

        // Turn off TXFE if all bytes are written.
        if (xfer->queued_len == xfer->total_len)
        {
          USB0.dtknqr4_fifoemptymsk &= ~(1 << n);
        }
      }

      // XFER Timeout
      if (USB0.in_ep_reg[n].diepint & USB_D_TIMEOUT0_M) {
        // Clear interrupt or enpoint will hang.
        USB0.in_ep_reg[n].diepint = USB_D_TIMEOUT0_M;
        // Maybe retry?
      }
    }
  }
}


static void _dcd_int_handler(void* arg)
{
  (void) arg;
  uint8_t const rhport = 0;

  const uint32_t int_status = USB0.gintsts;
  //const uint32_t int_msk = USB0.gintmsk;

  if (int_status & USB_USBRST_M) {
    // start of reset
    ESP_EARLY_LOGV(TAG, "dcd_int_handler - reset");
    USB0.gintsts = USB_USBRST_M;
    // FIFOs will be reassigned when the endpoints are reopen
    _allocated_fifos = 1;
    bus_reset();
  }

  if (int_status & USB_RESETDET_M) {
    ESP_EARLY_LOGV(TAG, "dcd_int_handler - reset while suspend");
    USB0.gintsts = USB_RESETDET_M;
    bus_reset();
  }

  if (int_status & USB_ENUMDONE_M) {
    // ENUMDNE detects speed of the link. For full-speed, we
    // always expect the same value. This interrupt is considered
    // the end of reset.
    USB0.gintsts = USB_ENUMDONE_M;
    enum_done_processing();
    dcd_event_bus_reset(rhport, TUSB_SPEED_FULL, true);
  }

  if(int_status & USB_USBSUSP_M)
  {
    USB0.gintsts = USB_USBSUSP_M;
    dcd_event_bus_signal(rhport, DCD_EVENT_SUSPEND, true);
  }

  if(int_status & USB_WKUPINT_M)
  {
    USB0.gintsts = USB_WKUPINT_M;
    dcd_event_bus_signal(rhport, DCD_EVENT_RESUME, true);
  }

  if (int_status & USB_OTGINT_M)
  {
    // OTG INT bit is read-only
    ESP_EARLY_LOGV(TAG, "dcd_int_handler - disconnected");

    uint32_t const otg_int = USB0.gotgint;

    if (otg_int & USB_SESENDDET_M)
    {
      dcd_event_bus_signal(rhport, DCD_EVENT_UNPLUGGED, true);
    }

    USB0.gotgint = otg_int;
  }

#if USE_SOF
  if (int_status & USB_SOF_M) {
    USB0.gintsts = USB_SOF_M;
    dcd_event_bus_signal(rhport, DCD_EVENT_SOF, true); // do nothing actually
  }
#endif

  if (int_status & USB_RXFLVI_M) {
    // RXFLVL bit is read-only
    ESP_EARLY_LOGV(TAG, "dcd_int_handler - rx!");

    // Mask out RXFLVL while reading data from FIFO
    USB0.gintmsk &= ~USB_RXFLVIMSK_M;
    read_rx_fifo();
    USB0.gintmsk |= USB_RXFLVIMSK_M;
  }

  // OUT endpoint interrupt handling.
  if (int_status & USB_OEPINT_M) {
    // OEPINT is read-only
    ESP_EARLY_LOGV(TAG, "dcd_int_handler - OUT endpoint!");
    handle_epout_ints();
  }

  // IN endpoint interrupt handling.
  if (int_status & USB_IEPINT_M) {
    // IEPINT bit read-only
    ESP_EARLY_LOGV(TAG, "dcd_int_handler - IN endpoint!");
    handle_epin_ints();
  }

  // Without handling
  USB0.gintsts |= USB_CURMOD_INT_M  |
                  USB_MODEMIS_M     |
                  USB_OTGINT_M      |
                  USB_NPTXFEMP_M    |
                  USB_GINNAKEFF_M   |
                  USB_GOUTNAKEFF    |
                  USB_ERLYSUSP_M    |
                  USB_USBSUSP_M     |
                  USB_ISOOUTDROP_M  |
                  USB_EOPF_M        |
                  USB_EPMIS_M       |
                  USB_INCOMPISOIN_M |
                  USB_INCOMPIP_M    |
                  USB_FETSUSP_M     |
                  USB_PTXFEMP_M;
}

void dcd_int_enable (uint8_t rhport)
{
  (void) rhport;
  esp_intr_alloc(ETS_USB_INTR_SOURCE, ESP_INTR_FLAG_LOWMED, (intr_handler_t) _dcd_int_handler, NULL, &usb_ih);
}

void dcd_int_disable (uint8_t rhport)
{
  (void) rhport;
  esp_intr_free(usb_ih);
}

#endif // #if OPT_MCU_ESP32S2 || OPT_MCU_ESP32S3

