staging: HCD files for the DWC2 driver

These files contain the HCD code, and implement the Linux
hc_driver API. Support for both slave mode and buffer DMA mode
of the controller is included.
Signed-off-by: NPaul Zimmerman <paulz@synopsys.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/dwc2/hcd_queue.c

+/*
+ * hcd_queue.c - DesignWare HS OTG Controller host queuing routines
+ *
+ * Copyright (C) 2004-2013 Synopsys, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions, and the following disclaimer,
+ *    without modification.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The names of the above-listed copyright holders may not be used
+ *    to endorse or promote products derived from this software without
+ *    specific prior written permission.
+ *
+ * ALTERNATIVELY, this software may be distributed under the terms of the
+ * GNU General Public License ("GPL") as published by the Free Software
+ * Foundation; either version 2 of the License, or (at your option) any
+ * later version.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+ * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/*
+ * This file contains the functions to manage Queue Heads and Queue
+ * Transfer Descriptors for Host mode
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+#include <linux/interrupt.h>
+#include <linux/dma-mapping.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+#include <linux/usb.h>
+
+#include <linux/usb/hcd.h>
+#include <linux/usb/ch11.h>
+
+#include "core.h"
+#include "hcd.h"
+
+/**
+ * dwc2_qh_init() - Initializes a QH structure
+ *
+ * @hsotg: The HCD state structure for the DWC OTG controller
+ * @qh:    The QH to init
+ * @urb:   Holds the information about the device/endpoint needed to initialize
+ *         the QH
+ */
+#define SCHEDULE_SLOP 10
+static void dwc2_qh_init(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh,
+			 struct dwc2_hcd_urb *urb)
+{
+	int dev_speed, hub_addr, hub_port;
+	char *speed, *type;
+
+	dev_vdbg(hsotg->dev, "%s()\n", __func__);
+
+	/* Initialize QH */
+	qh->ep_type = dwc2_hcd_get_pipe_type(&urb->pipe_info);
+	qh->ep_is_in = dwc2_hcd_is_pipe_in(&urb->pipe_info) ? 1 : 0;
+
+	qh->data_toggle = DWC2_HC_PID_DATA0;
+	qh->maxp = dwc2_hcd_get_mps(&urb->pipe_info);
+	INIT_LIST_HEAD(&qh->qtd_list);
+	INIT_LIST_HEAD(&qh->qh_list_entry);
+
+	/* FS/LS Endpoint on HS Hub, NOT virtual root hub */
+	dev_speed = dwc2_host_get_speed(hsotg, urb->priv);
+
+	dwc2_host_hub_info(hsotg, urb->priv, &hub_addr, &hub_port);
+
+	if ((dev_speed == USB_SPEED_LOW || dev_speed == USB_SPEED_FULL) &&
+	    hub_addr != 0 && hub_addr != 1) {
+		dev_vdbg(hsotg->dev,
+			 "QH init: EP %d: TT found at hub addr %d, for port %d\n",
+			 dwc2_hcd_get_ep_num(&urb->pipe_info), hub_addr,
+			 hub_port);
+		qh->do_split = 1;
+	}
+
+	if (qh->ep_type == USB_ENDPOINT_XFER_INT ||
+	    qh->ep_type == USB_ENDPOINT_XFER_ISOC) {
+		/* Compute scheduling parameters once and save them */
+		u32 hprt, prtspd;
+
+		/* Todo: Account for split transfers in the bus time */
+		int bytecount =
+			dwc2_hb_mult(qh->maxp) * dwc2_max_packet(qh->maxp);
+
+		qh->usecs = NS_TO_US(usb_calc_bus_time(qh->do_split ?
+				USB_SPEED_HIGH : dev_speed, qh->ep_is_in,
+				qh->ep_type == USB_ENDPOINT_XFER_ISOC,
+				bytecount));
+		/* Start in a slightly future (micro)frame */
+		qh->sched_frame = dwc2_frame_num_inc(hsotg->frame_number,
+						     SCHEDULE_SLOP);
+		qh->interval = urb->interval;
+#if 0
+		/* Increase interrupt polling rate for debugging */
+		if (qh->ep_type == USB_ENDPOINT_XFER_INT)
+			qh->interval = 8;
+#endif
+		hprt = readl(hsotg->regs + HPRT0);
+		prtspd = hprt & HPRT0_SPD_MASK;
+		if (prtspd == HPRT0_SPD_HIGH_SPEED &&
+		    (dev_speed == USB_SPEED_LOW ||
+		     dev_speed == USB_SPEED_FULL)) {
+			qh->interval *= 8;
+			qh->sched_frame |= 0x7;
+			qh->start_split_frame = qh->sched_frame;
+		}
+		dev_dbg(hsotg->dev, "interval=%d\n", qh->interval);
+	}
+
+	dev_vdbg(hsotg->dev, "DWC OTG HCD QH Initialized\n");
+	dev_vdbg(hsotg->dev, "DWC OTG HCD QH - qh = %p\n", qh);
+	dev_vdbg(hsotg->dev, "DWC OTG HCD QH - Device Address = %d\n",
+		 dwc2_hcd_get_dev_addr(&urb->pipe_info));
+	dev_vdbg(hsotg->dev, "DWC OTG HCD QH - Endpoint %d, %s\n",
+		 dwc2_hcd_get_ep_num(&urb->pipe_info),
+		 dwc2_hcd_is_pipe_in(&urb->pipe_info) ? "IN" : "OUT");
+
+	qh->dev_speed = dev_speed;
+
+	switch (dev_speed) {
+	case USB_SPEED_LOW:
+		speed = "low";
+		break;
+	case USB_SPEED_FULL:
+		speed = "full";
+		break;
+	case USB_SPEED_HIGH:
+		speed = "high";
+		break;
+	default:
+		speed = "?";
+		break;
+	}
+	dev_vdbg(hsotg->dev, "DWC OTG HCD QH - Speed = %s\n", speed);
+
+	switch (qh->ep_type) {
+	case USB_ENDPOINT_XFER_ISOC:
+		type = "isochronous";
+		break;
+	case USB_ENDPOINT_XFER_INT:
+		type = "interrupt";
+		break;
+	case USB_ENDPOINT_XFER_CONTROL:
+		type = "control";
+		break;
+	case USB_ENDPOINT_XFER_BULK:
+		type = "bulk";
+		break;
+	default:
+		type = "?";
+		break;
+	}
+
+	dev_vdbg(hsotg->dev, "DWC OTG HCD QH - Type = %s\n", type);
+
+	if (qh->ep_type == USB_ENDPOINT_XFER_INT) {
+		dev_vdbg(hsotg->dev, "DWC OTG HCD QH - usecs = %d\n",
+			 qh->usecs);
+		dev_vdbg(hsotg->dev, "DWC OTG HCD QH - interval = %d\n",
+			 qh->interval);
+	}
+}
+
+/**
+ * dwc2_hcd_qh_create() - Allocates and initializes a QH
+ *
+ * @hsotg:        The HCD state structure for the DWC OTG controller
+ * @urb:          Holds the information about the device/endpoint needed
+ *                to initialize the QH
+ * @atomic_alloc: Flag to do atomic allocation if needed
+ *
+ * Return: Pointer to the newly allocated QH, or NULL on error
+ */
+static struct dwc2_qh *dwc2_hcd_qh_create(struct dwc2_hsotg *hsotg,
+					  struct dwc2_hcd_urb *urb,
+					  gfp_t mem_flags)
+{
+	struct dwc2_qh *qh;
+
+	/* Allocate memory */
+	qh = kzalloc(sizeof(*qh), mem_flags);
+	if (!qh)
+		return NULL;
+
+	dwc2_qh_init(hsotg, qh, urb);
+
+	if (hsotg->core_params->dma_desc_enable > 0 &&
+	    dwc2_hcd_qh_init_ddma(hsotg, qh, mem_flags) < 0) {
+		dwc2_hcd_qh_free(hsotg, qh);
+		return NULL;
+	}
+
+	return qh;
+}
+
+/**
+ * dwc2_hcd_qh_free() - Frees the QH
+ *
+ * @hsotg: HCD instance
+ * @qh:    The QH to free
+ *
+ * QH should already be removed from the list. QTD list should already be empty
+ * if called from URB Dequeue.
+ *
+ * Must NOT be called with interrupt disabled or spinlock held
+ */
+void dwc2_hcd_qh_free(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
+{
+	u32 buf_size;
+
+	if (hsotg->core_params->dma_desc_enable > 0) {
+		dwc2_hcd_qh_free_ddma(hsotg, qh);
+	} else if (qh->dw_align_buf) {
+		if (qh->ep_type == USB_ENDPOINT_XFER_ISOC)
+			buf_size = 4096;
+		else
+			buf_size = hsotg->core_params->max_transfer_size;
+		dma_free_coherent(hsotg->dev, buf_size, qh->dw_align_buf,
+				  qh->dw_align_buf_dma);
+	}
+
+	kfree(qh);
+}
+
+/**
+ * dwc2_periodic_channel_available() - Checks that a channel is available for a
+ * periodic transfer
+ *
+ * @hsotg: The HCD state structure for the DWC OTG controller
+ *
+ * Return: 0 if successful, negative error code otherise
+ */
+static int dwc2_periodic_channel_available(struct dwc2_hsotg *hsotg)
+{
+	/*
+	 * Currently assuming that there is a dedicated host channnel for
+	 * each periodic transaction plus at least one host channel for
+	 * non-periodic transactions
+	 */
+	int status;
+	int num_channels;
+
+	num_channels = hsotg->core_params->host_channels;
+	if (hsotg->periodic_channels + hsotg->non_periodic_channels <
+								num_channels
+	    && hsotg->periodic_channels < num_channels - 1) {
+		status = 0;
+	} else {
+		dev_dbg(hsotg->dev,
+			"%s: Total channels: %d, Periodic: %d, "
+			"Non-periodic: %d\n", __func__, num_channels,
+			hsotg->periodic_channels, hsotg->non_periodic_channels);
+		status = -ENOSPC;
+	}
+
+	return status;
+}
+
+/**
+ * dwc2_check_periodic_bandwidth() - Checks that there is sufficient bandwidth
+ * for the specified QH in the periodic schedule
+ *
+ * @hsotg: The HCD state structure for the DWC OTG controller
+ * @qh:    QH containing periodic bandwidth required
+ *
+ * Return: 0 if successful, negative error code otherwise
+ *
+ * For simplicity, this calculation assumes that all the transfers in the
+ * periodic schedule may occur in the same (micro)frame
+ */
+static int dwc2_check_periodic_bandwidth(struct dwc2_hsotg *hsotg,
+					 struct dwc2_qh *qh)
+{
+	int status;
+	s16 max_claimed_usecs;
+
+	status = 0;
+
+	if (qh->dev_speed == USB_SPEED_HIGH || qh->do_split) {
+		/*
+		 * High speed mode
+		 * Max periodic usecs is 80% x 125 usec = 100 usec
+		 */
+		max_claimed_usecs = 100 - qh->usecs;
+	} else {
+		/*
+		 * Full speed mode
+		 * Max periodic usecs is 90% x 1000 usec = 900 usec
+		 */
+		max_claimed_usecs = 900 - qh->usecs;
+	}
+
+	if (hsotg->periodic_usecs > max_claimed_usecs) {
+		dev_err(hsotg->dev,
+			"%s: already claimed usecs %d, required usecs %d\n",
+			__func__, hsotg->periodic_usecs, qh->usecs);
+		status = -ENOSPC;
+	}
+
+	return status;
+}
+
+/**
+ * dwc2_check_max_xfer_size() - Checks that the max transfer size allowed in a
+ * host channel is large enough to handle the maximum data transfer in a single
+ * (micro)frame for a periodic transfer
+ *
+ * @hsotg: The HCD state structure for the DWC OTG controller
+ * @qh:    QH for a periodic endpoint
+ *
+ * Return: 0 if successful, negative error code otherwise
+ */
+static int dwc2_check_max_xfer_size(struct dwc2_hsotg *hsotg,
+				    struct dwc2_qh *qh)
+{
+	u32 max_xfer_size;
+	u32 max_channel_xfer_size;
+	int status = 0;
+
+	max_xfer_size = dwc2_max_packet(qh->maxp) * dwc2_hb_mult(qh->maxp);
+	max_channel_xfer_size = hsotg->core_params->max_transfer_size;
+
+	if (max_xfer_size > max_channel_xfer_size) {
+		dev_err(hsotg->dev,
+			"%s: Periodic xfer length %d > max xfer length for channel %d\n",
+			__func__, max_xfer_size, max_channel_xfer_size);
+		status = -ENOSPC;
+	}
+
+	return status;
+}
+
+/**
+ * dwc2_schedule_periodic() - Schedules an interrupt or isochronous transfer in
+ * the periodic schedule
+ *
+ * @hsotg: The HCD state structure for the DWC OTG controller
+ * @qh:    QH for the periodic transfer. The QH should already contain the
+ *         scheduling information.
+ *
+ * Return: 0 if successful, negative error code otherwise
+ */
+static int dwc2_schedule_periodic(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
+{
+	int status;
+
+	status = dwc2_periodic_channel_available(hsotg);
+	if (status) {
+		dev_dbg(hsotg->dev,
+			"%s: No host channel available for periodic transfer\n",
+			__func__);
+		return status;
+	}
+
+	status = dwc2_check_periodic_bandwidth(hsotg, qh);
+	if (status) {
+		dev_dbg(hsotg->dev,
+			"%s: Insufficient periodic bandwidth for periodic transfer\n",
+			__func__);
+		return status;
+	}
+
+	status = dwc2_check_max_xfer_size(hsotg, qh);
+	if (status) {
+		dev_dbg(hsotg->dev,
+			"%s: Channel max transfer size too small for periodic transfer\n",
+			__func__);
+		return status;
+	}
+
+	if (hsotg->core_params->dma_desc_enable > 0)
+		/* Don't rely on SOF and start in ready schedule */
+		list_add_tail(&qh->qh_list_entry, &hsotg->periodic_sched_ready);
+	else
+		/* Always start in inactive schedule */
+		list_add_tail(&qh->qh_list_entry,
+			      &hsotg->periodic_sched_inactive);
+
+	/* Reserve periodic channel */
+	hsotg->periodic_channels++;
+
+	/* Update claimed usecs per (micro)frame */
+	hsotg->periodic_usecs += qh->usecs;
+
+	return status;
+}
+
+/**
+ * dwc2_deschedule_periodic() - Removes an interrupt or isochronous transfer
+ * from the periodic schedule
+ *
+ * @hsotg: The HCD state structure for the DWC OTG controller
+ * @qh:	   QH for the periodic transfer
+ */
+static void dwc2_deschedule_periodic(struct dwc2_hsotg *hsotg,
+				     struct dwc2_qh *qh)
+{
+	list_del_init(&qh->qh_list_entry);
+
+	/* Release periodic channel reservation */
+	hsotg->periodic_channels--;
+
+	/* Update claimed usecs per (micro)frame */
+	hsotg->periodic_usecs -= qh->usecs;
+}
+
+/**
+ * dwc2_hcd_qh_add() - Adds a QH to either the non periodic or periodic
+ * schedule if it is not already in the schedule. If the QH is already in
+ * the schedule, no action is taken.
+ *
+ * @hsotg: The HCD state structure for the DWC OTG controller
+ * @qh:    The QH to add
+ *
+ * Return: 0 if successful, negative error code otherwise
+ */
+int dwc2_hcd_qh_add(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
+{
+	int status = 0;
+	u32 intr_mask;
+
+	dev_vdbg(hsotg->dev, "%s()\n", __func__);
+
+	if (!list_empty(&qh->qh_list_entry))
+		/* QH already in a schedule */
+		return status;
+
+	/* Add the new QH to the appropriate schedule */
+	if (dwc2_qh_is_non_per(qh)) {
+		/* Always start in inactive schedule */
+		list_add_tail(&qh->qh_list_entry,
+			      &hsotg->non_periodic_sched_inactive);
+	} else {
+		status = dwc2_schedule_periodic(hsotg, qh);
+		if (status == 0) {
+			if (!hsotg->periodic_qh_count) {
+				intr_mask = readl(hsotg->regs + GINTMSK);
+				intr_mask |= GINTSTS_SOF;
+				writel(intr_mask, hsotg->regs + GINTMSK);
+			}
+			hsotg->periodic_qh_count++;
+		}
+	}
+
+	return status;
+}
+
+/**
+ * dwc2_hcd_qh_unlink() - Removes a QH from either the non-periodic or periodic
+ * schedule. Memory is not freed.
+ *
+ * @hsotg: The HCD state structure
+ * @qh:    QH to remove from schedule
+ */
+void dwc2_hcd_qh_unlink(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
+{
+	u32 intr_mask;
+
+	dev_vdbg(hsotg->dev, "%s()\n", __func__);
+
+	if (list_empty(&qh->qh_list_entry))
+		/* QH is not in a schedule */
+		return;
+
+	if (dwc2_qh_is_non_per(qh)) {
+		if (hsotg->non_periodic_qh_ptr == &qh->qh_list_entry)
+			hsotg->non_periodic_qh_ptr =
+					hsotg->non_periodic_qh_ptr->next;
+		list_del_init(&qh->qh_list_entry);
+	} else {
+		dwc2_deschedule_periodic(hsotg, qh);
+		hsotg->periodic_qh_count--;
+		if (!hsotg->periodic_qh_count) {
+			intr_mask = readl(hsotg->regs + GINTMSK);
+			intr_mask &= ~GINTSTS_SOF;
+			writel(intr_mask, hsotg->regs + GINTMSK);
+		}
+	}
+}
+
+/*
+ * Schedule the next continuing periodic split transfer
+ */
+static void dwc2_sched_periodic_split(struct dwc2_hsotg *hsotg,
+				      struct dwc2_qh *qh, u16 frame_number,
+				      int sched_next_periodic_split)
+{
+	u16 incr;
+
+	if (sched_next_periodic_split) {
+		qh->sched_frame = frame_number;
+		incr = dwc2_frame_num_inc(qh->start_split_frame, 1);
+		if (dwc2_frame_num_le(frame_number, incr)) {
+			/*
+			 * Allow one frame to elapse after start split
+			 * microframe before scheduling complete split, but
+			 * DON'T if we are doing the next start split in the
+			 * same frame for an ISOC out
+			 */
+			if (qh->ep_type != USB_ENDPOINT_XFER_ISOC ||
+			    qh->ep_is_in != 0) {
+				qh->sched_frame =
+					dwc2_frame_num_inc(qh->sched_frame, 1);
+			}
+		}
+	} else {
+		qh->sched_frame = dwc2_frame_num_inc(qh->start_split_frame,
+						     qh->interval);
+		if (dwc2_frame_num_le(qh->sched_frame, frame_number))
+			qh->sched_frame = frame_number;
+		qh->sched_frame |= 0x7;
+		qh->start_split_frame = qh->sched_frame;
+	}
+}
+
+/*
+ * Deactivates a QH. For non-periodic QHs, removes the QH from the active
+ * non-periodic schedule. The QH is added to the inactive non-periodic
+ * schedule if any QTDs are still attached to the QH.
+ *
+ * For periodic QHs, the QH is removed from the periodic queued schedule. If
+ * there are any QTDs still attached to the QH, the QH is added to either the
+ * periodic inactive schedule or the periodic ready schedule and its next
+ * scheduled frame is calculated. The QH is placed in the ready schedule if
+ * the scheduled frame has been reached already. Otherwise it's placed in the
+ * inactive schedule. If there are no QTDs attached to the QH, the QH is
+ * completely removed from the periodic schedule.
+ */
+void dwc2_hcd_qh_deactivate(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh,
+			    int sched_next_periodic_split)
+{
+	dev_vdbg(hsotg->dev, "%s()\n", __func__);
+
+	if (dwc2_qh_is_non_per(qh)) {
+		dwc2_hcd_qh_unlink(hsotg, qh);
+		if (!list_empty(&qh->qtd_list))
+			/* Add back to inactive non-periodic schedule */
+			dwc2_hcd_qh_add(hsotg, qh);
+	} else {
+		u16 frame_number = dwc2_hcd_get_frame_number(hsotg);
+
+		if (qh->do_split) {
+			dwc2_sched_periodic_split(hsotg, qh, frame_number,
+						  sched_next_periodic_split);
+		} else {
+			qh->sched_frame = dwc2_frame_num_inc(qh->sched_frame,
+							     qh->interval);
+			if (dwc2_frame_num_le(qh->sched_frame, frame_number))
+				qh->sched_frame = frame_number;
+		}
+
+		if (list_empty(&qh->qtd_list)) {
+			dwc2_hcd_qh_unlink(hsotg, qh);
+		} else {
+			/*
+			 * Remove from periodic_sched_queued and move to
+			 * appropriate queue
+			 */
+			if (qh->sched_frame == frame_number)
+				list_move(&qh->qh_list_entry,
+					  &hsotg->periodic_sched_ready);
+			else
+				list_move(&qh->qh_list_entry,
+					  &hsotg->periodic_sched_inactive);
+		}
+	}
+}
+
+/**
+ * dwc2_hcd_qtd_init() - Initializes a QTD structure
+ *
+ * @qtd: The QTD to initialize
+ * @urb: The associated URB
+ */
+void dwc2_hcd_qtd_init(struct dwc2_qtd *qtd, struct dwc2_hcd_urb *urb)
+{
+	qtd->urb = urb;
+	if (dwc2_hcd_get_pipe_type(&urb->pipe_info) ==
+			USB_ENDPOINT_XFER_CONTROL) {
+		/*
+		 * The only time the QTD data toggle is used is on the data
+		 * phase of control transfers. This phase always starts with
+		 * DATA1.
+		 */
+		qtd->data_toggle = DWC2_HC_PID_DATA1;
+		qtd->control_phase = DWC2_CONTROL_SETUP;
+	}
+
+	/* Start split */
+	qtd->complete_split = 0;
+	qtd->isoc_split_pos = DWC2_HCSPLT_XACTPOS_ALL;
+	qtd->isoc_split_offset = 0;
+	qtd->in_process = 0;
+
+	/* Store the qtd ptr in the urb to reference the QTD */
+	urb->qtd = qtd;
+}
+
+/**
+ * dwc2_hcd_qtd_add() - Adds a QTD to the QTD-list of a QH
+ *
+ * @hsotg:        The DWC HCD structure
+ * @qtd:          The QTD to add
+ * @qh:           Out parameter to return queue head
+ * @atomic_alloc: Flag to do atomic alloc if needed
+ *
+ * Return: 0 if successful, negative error code otherwise
+ *
+ * Finds the correct QH to place the QTD into. If it does not find a QH, it
+ * will create a new QH. If the QH to which the QTD is added is not currently
+ * scheduled, it is placed into the proper schedule based on its EP type.
+ */
+int dwc2_hcd_qtd_add(struct dwc2_hsotg *hsotg, struct dwc2_qtd *qtd,
+		     struct dwc2_qh **qh, gfp_t mem_flags)
+{
+	struct dwc2_hcd_urb *urb = qtd->urb;
+	unsigned long flags;
+	int allocated = 0;
+	int retval = 0;
+
+	/*
+	 * Get the QH which holds the QTD-list to insert to. Create QH if it
+	 * doesn't exist.
+	 */
+	if (*qh == NULL) {
+		*qh = dwc2_hcd_qh_create(hsotg, urb, mem_flags);
+		if (*qh == NULL)
+			return -ENOMEM;
+		allocated = 1;
+	}
+
+	spin_lock_irqsave(&hsotg->lock, flags);
+	retval = dwc2_hcd_qh_add(hsotg, *qh);
+	if (retval && allocated) {
+		struct dwc2_qtd *qtd2, *qtd2_tmp;
+		struct dwc2_qh *qh_tmp = *qh;
+
+		*qh = NULL;
+		dwc2_hcd_qh_unlink(hsotg, qh_tmp);
+
+		/* Free each QTD in the QH's QTD list */
+		list_for_each_entry_safe(qtd2, qtd2_tmp, &qh_tmp->qtd_list,
+					 qtd_list_entry)
+			dwc2_hcd_qtd_unlink_and_free(hsotg, qtd2, qh_tmp);
+
+		spin_unlock_irqrestore(&hsotg->lock, flags);
+		dwc2_hcd_qh_free(hsotg, qh_tmp);
+	} else {
+		qtd->qh = *qh;
+		list_add_tail(&qtd->qtd_list_entry, &(*qh)->qtd_list);
+		spin_unlock_irqrestore(&hsotg->lock, flags);
+	}
+
+	return retval;
+}