1 files changed, 1004 insertions, 0 deletions

diff --git a/drivers/usb/host/xhci-dbgcap.c b/drivers/usb/host/xhci-dbgcap.c
new file mode 100644
index 000000000..ba841c569
--- /dev/null
+++ b/drivers/usb/host/xhci-dbgcap.c
@@ -0,0 +1,1004 @@
+// SPDX-License-Identifier: GPL-2.0
+/**
+ * xhci-dbgcap.c - xHCI debug capability support
+ *
+ * Copyright (C) 2017 Intel Corporation
+ *
+ * Author: Lu Baolu <baolu.lu@linux.intel.com>
+ */
+#include <linux/dma-mapping.h>
+#include <linux/slab.h>
+#include <linux/nls.h>
+
+#include "xhci.h"
+#include "xhci-trace.h"
+#include "xhci-dbgcap.h"
+
+static inline void *
+dbc_dma_alloc_coherent(struct xhci_hcd *xhci, size_t size,
+		       dma_addr_t *dma_handle, gfp_t flags)
+{
+	void		*vaddr;
+
+	vaddr = dma_alloc_coherent(xhci_to_hcd(xhci)->self.sysdev,
+				   size, dma_handle, flags);
+	memset(vaddr, 0, size);
+	return vaddr;
+}
+
+static inline void
+dbc_dma_free_coherent(struct xhci_hcd *xhci, size_t size,
+		      void *cpu_addr, dma_addr_t dma_handle)
+{
+	if (cpu_addr)
+		dma_free_coherent(xhci_to_hcd(xhci)->self.sysdev,
+				  size, cpu_addr, dma_handle);
+}
+
+static u32 xhci_dbc_populate_strings(struct dbc_str_descs *strings)
+{
+	struct usb_string_descriptor	*s_desc;
+	u32				string_length;
+
+	/* Serial string: */
+	s_desc = (struct usb_string_descriptor *)strings->serial;
+	utf8s_to_utf16s(DBC_STRING_SERIAL, strlen(DBC_STRING_SERIAL),
+			UTF16_LITTLE_ENDIAN, (wchar_t *)s_desc->wData,
+			DBC_MAX_STRING_LENGTH);
+
+	s_desc->bLength		= (strlen(DBC_STRING_SERIAL) + 1) * 2;
+	s_desc->bDescriptorType	= USB_DT_STRING;
+	string_length		= s_desc->bLength;
+	string_length		<<= 8;
+
+	/* Product string: */
+	s_desc = (struct usb_string_descriptor *)strings->product;
+	utf8s_to_utf16s(DBC_STRING_PRODUCT, strlen(DBC_STRING_PRODUCT),
+			UTF16_LITTLE_ENDIAN, (wchar_t *)s_desc->wData,
+			DBC_MAX_STRING_LENGTH);
+
+	s_desc->bLength		= (strlen(DBC_STRING_PRODUCT) + 1) * 2;
+	s_desc->bDescriptorType	= USB_DT_STRING;
+	string_length		+= s_desc->bLength;
+	string_length		<<= 8;
+
+	/* Manufacture string: */
+	s_desc = (struct usb_string_descriptor *)strings->manufacturer;
+	utf8s_to_utf16s(DBC_STRING_MANUFACTURER,
+			strlen(DBC_STRING_MANUFACTURER),
+			UTF16_LITTLE_ENDIAN, (wchar_t *)s_desc->wData,
+			DBC_MAX_STRING_LENGTH);
+
+	s_desc->bLength		= (strlen(DBC_STRING_MANUFACTURER) + 1) * 2;
+	s_desc->bDescriptorType	= USB_DT_STRING;
+	string_length		+= s_desc->bLength;
+	string_length		<<= 8;
+
+	/* String0: */
+	strings->string0[0]	= 4;
+	strings->string0[1]	= USB_DT_STRING;
+	strings->string0[2]	= 0x09;
+	strings->string0[3]	= 0x04;
+	string_length		+= 4;
+
+	return string_length;
+}
+
+static void xhci_dbc_init_contexts(struct xhci_hcd *xhci, u32 string_length)
+{
+	struct xhci_dbc		*dbc;
+	struct dbc_info_context	*info;
+	struct xhci_ep_ctx	*ep_ctx;
+	u32			dev_info;
+	dma_addr_t		deq, dma;
+	unsigned int		max_burst;
+
+	dbc = xhci->dbc;
+	if (!dbc)
+		return;
+
+	/* Populate info Context: */
+	info			= (struct dbc_info_context *)dbc->ctx->bytes;
+	dma			= dbc->string_dma;
+	info->string0		= cpu_to_le64(dma);
+	info->manufacturer	= cpu_to_le64(dma + DBC_MAX_STRING_LENGTH);
+	info->product		= cpu_to_le64(dma + DBC_MAX_STRING_LENGTH * 2);
+	info->serial		= cpu_to_le64(dma + DBC_MAX_STRING_LENGTH * 3);
+	info->length		= cpu_to_le32(string_length);
+
+	/* Populate bulk out endpoint context: */
+	ep_ctx			= dbc_bulkout_ctx(dbc);
+	max_burst		= DBC_CTRL_MAXBURST(readl(&dbc->regs->control));
+	deq			= dbc_bulkout_enq(dbc);
+	ep_ctx->ep_info		= 0;
+	ep_ctx->ep_info2	= dbc_epctx_info2(BULK_OUT_EP, 1024, max_burst);
+	ep_ctx->deq		= cpu_to_le64(deq | dbc->ring_out->cycle_state);
+
+	/* Populate bulk in endpoint context: */
+	ep_ctx			= dbc_bulkin_ctx(dbc);
+	deq			= dbc_bulkin_enq(dbc);
+	ep_ctx->ep_info		= 0;
+	ep_ctx->ep_info2	= dbc_epctx_info2(BULK_IN_EP, 1024, max_burst);
+	ep_ctx->deq		= cpu_to_le64(deq | dbc->ring_in->cycle_state);
+
+	/* Set DbC context and info registers: */
+	xhci_write_64(xhci, dbc->ctx->dma, &dbc->regs->dccp);
+
+	dev_info = cpu_to_le32((DBC_VENDOR_ID << 16) | DBC_PROTOCOL);
+	writel(dev_info, &dbc->regs->devinfo1);
+
+	dev_info = cpu_to_le32((DBC_DEVICE_REV << 16) | DBC_PRODUCT_ID);
+	writel(dev_info, &dbc->regs->devinfo2);
+}
+
+static void xhci_dbc_giveback(struct dbc_request *req, int status)
+	__releases(&dbc->lock)
+	__acquires(&dbc->lock)
+{
+	struct dbc_ep		*dep = req->dep;
+	struct xhci_dbc		*dbc = dep->dbc;
+	struct xhci_hcd		*xhci = dbc->xhci;
+	struct device		*dev = xhci_to_hcd(dbc->xhci)->self.sysdev;
+
+	list_del_init(&req->list_pending);
+	req->trb_dma = 0;
+	req->trb = NULL;
+
+	if (req->status == -EINPROGRESS)
+		req->status = status;
+
+	trace_xhci_dbc_giveback_request(req);
+
+	dma_unmap_single(dev,
+			 req->dma,
+			 req->length,
+			 dbc_ep_dma_direction(dep));
+
+	/* Give back the transfer request: */
+	spin_unlock(&dbc->lock);
+	req->complete(xhci, req);
+	spin_lock(&dbc->lock);
+}
+
+static void xhci_dbc_flush_single_request(struct dbc_request *req)
+{
+	union xhci_trb	*trb = req->trb;
+
+	trb->generic.field[0]	= 0;
+	trb->generic.field[1]	= 0;
+	trb->generic.field[2]	= 0;
+	trb->generic.field[3]	&= cpu_to_le32(TRB_CYCLE);
+	trb->generic.field[3]	|= cpu_to_le32(TRB_TYPE(TRB_TR_NOOP));
+
+	xhci_dbc_giveback(req, -ESHUTDOWN);
+}
+
+static void xhci_dbc_flush_endpoint_requests(struct dbc_ep *dep)
+{
+	struct dbc_request	*req, *tmp;
+
+	list_for_each_entry_safe(req, tmp, &dep->list_pending, list_pending)
+		xhci_dbc_flush_single_request(req);
+}
+
+static void xhci_dbc_flush_reqests(struct xhci_dbc *dbc)
+{
+	xhci_dbc_flush_endpoint_requests(&dbc->eps[BULK_OUT]);
+	xhci_dbc_flush_endpoint_requests(&dbc->eps[BULK_IN]);
+}
+
+struct dbc_request *
+dbc_alloc_request(struct dbc_ep *dep, gfp_t gfp_flags)
+{
+	struct dbc_request	*req;
+
+	req = kzalloc(sizeof(*req), gfp_flags);
+	if (!req)
+		return NULL;
+
+	req->dep = dep;
+	INIT_LIST_HEAD(&req->list_pending);
+	INIT_LIST_HEAD(&req->list_pool);
+	req->direction = dep->direction;
+
+	trace_xhci_dbc_alloc_request(req);
+
+	return req;
+}
+
+void
+dbc_free_request(struct dbc_ep *dep, struct dbc_request *req)
+{
+	trace_xhci_dbc_free_request(req);
+
+	kfree(req);
+}
+
+static void
+xhci_dbc_queue_trb(struct xhci_ring *ring, u32 field1,
+		   u32 field2, u32 field3, u32 field4)
+{
+	union xhci_trb		*trb, *next;
+
+	trb = ring->enqueue;
+	trb->generic.field[0]	= cpu_to_le32(field1);
+	trb->generic.field[1]	= cpu_to_le32(field2);
+	trb->generic.field[2]	= cpu_to_le32(field3);
+	trb->generic.field[3]	= cpu_to_le32(field4);
+
+	trace_xhci_dbc_gadget_ep_queue(ring, &trb->generic);
+
+	ring->num_trbs_free--;
+	next = ++(ring->enqueue);
+	if (TRB_TYPE_LINK_LE32(next->link.control)) {
+		next->link.control ^= cpu_to_le32(TRB_CYCLE);
+		ring->enqueue = ring->enq_seg->trbs;
+		ring->cycle_state ^= 1;
+	}
+}
+
+static int xhci_dbc_queue_bulk_tx(struct dbc_ep *dep,
+				  struct dbc_request *req)
+{
+	u64			addr;
+	union xhci_trb		*trb;
+	unsigned int		num_trbs;
+	struct xhci_dbc		*dbc = dep->dbc;
+	struct xhci_ring	*ring = dep->ring;
+	u32			length, control, cycle;
+
+	num_trbs = count_trbs(req->dma, req->length);
+	WARN_ON(num_trbs != 1);
+	if (ring->num_trbs_free < num_trbs)
+		return -EBUSY;
+
+	addr	= req->dma;
+	trb	= ring->enqueue;
+	cycle	= ring->cycle_state;
+	length	= TRB_LEN(req->length);
+	control	= TRB_TYPE(TRB_NORMAL) | TRB_IOC;
+
+	if (cycle)
+		control &= cpu_to_le32(~TRB_CYCLE);
+	else
+		control |= cpu_to_le32(TRB_CYCLE);
+
+	req->trb = ring->enqueue;
+	req->trb_dma = xhci_trb_virt_to_dma(ring->enq_seg, ring->enqueue);
+	xhci_dbc_queue_trb(ring,
+			   lower_32_bits(addr),
+			   upper_32_bits(addr),
+			   length, control);
+
+	/*
+	 * Add a barrier between writes of trb fields and flipping
+	 * the cycle bit:
+	 */
+	wmb();
+
+	if (cycle)
+		trb->generic.field[3] |= cpu_to_le32(TRB_CYCLE);
+	else
+		trb->generic.field[3] &= cpu_to_le32(~TRB_CYCLE);
+
+	writel(DBC_DOOR_BELL_TARGET(dep->direction), &dbc->regs->doorbell);
+
+	return 0;
+}
+
+static int
+dbc_ep_do_queue(struct dbc_ep *dep, struct dbc_request *req)
+{
+	int			ret;
+	struct device		*dev;
+	struct xhci_dbc		*dbc = dep->dbc;
+	struct xhci_hcd		*xhci = dbc->xhci;
+
+	dev = xhci_to_hcd(xhci)->self.sysdev;
+
+	if (!req->length || !req->buf)
+		return -EINVAL;
+
+	req->actual		= 0;
+	req->status		= -EINPROGRESS;
+
+	req->dma = dma_map_single(dev,
+				  req->buf,
+				  req->length,
+				  dbc_ep_dma_direction(dep));
+	if (dma_mapping_error(dev, req->dma)) {
+		xhci_err(xhci, "failed to map buffer\n");
+		return -EFAULT;
+	}
+
+	ret = xhci_dbc_queue_bulk_tx(dep, req);
+	if (ret) {
+		xhci_err(xhci, "failed to queue trbs\n");
+		dma_unmap_single(dev,
+				 req->dma,
+				 req->length,
+				 dbc_ep_dma_direction(dep));
+		return -EFAULT;
+	}
+
+	list_add_tail(&req->list_pending, &dep->list_pending);
+
+	return 0;
+}
+
+int dbc_ep_queue(struct dbc_ep *dep, struct dbc_request *req,
+		 gfp_t gfp_flags)
+{
+	unsigned long		flags;
+	struct xhci_dbc		*dbc = dep->dbc;
+	int			ret = -ESHUTDOWN;
+
+	spin_lock_irqsave(&dbc->lock, flags);
+	if (dbc->state == DS_CONFIGURED)
+		ret = dbc_ep_do_queue(dep, req);
+	spin_unlock_irqrestore(&dbc->lock, flags);
+
+	mod_delayed_work(system_wq, &dbc->event_work, 0);
+
+	trace_xhci_dbc_queue_request(req);
+
+	return ret;
+}
+
+static inline void xhci_dbc_do_eps_init(struct xhci_hcd *xhci, bool direction)
+{
+	struct dbc_ep		*dep;
+	struct xhci_dbc		*dbc = xhci->dbc;
+
+	dep			= &dbc->eps[direction];
+	dep->dbc		= dbc;
+	dep->direction		= direction;
+	dep->ring		= direction ? dbc->ring_in : dbc->ring_out;
+
+	INIT_LIST_HEAD(&dep->list_pending);
+}
+
+static void xhci_dbc_eps_init(struct xhci_hcd *xhci)
+{
+	xhci_dbc_do_eps_init(xhci, BULK_OUT);
+	xhci_dbc_do_eps_init(xhci, BULK_IN);
+}
+
+static void xhci_dbc_eps_exit(struct xhci_hcd *xhci)
+{
+	struct xhci_dbc		*dbc = xhci->dbc;
+
+	memset(dbc->eps, 0, sizeof(struct dbc_ep) * ARRAY_SIZE(dbc->eps));
+}
+
+static int xhci_dbc_mem_init(struct xhci_hcd *xhci, gfp_t flags)
+{
+	int			ret;
+	dma_addr_t		deq;
+	u32			string_length;
+	struct xhci_dbc		*dbc = xhci->dbc;
+
+	/* Allocate various rings for events and transfers: */
+	dbc->ring_evt = xhci_ring_alloc(xhci, 1, 1, TYPE_EVENT, 0, flags);
+	if (!dbc->ring_evt)
+		goto evt_fail;
+
+	dbc->ring_in = xhci_ring_alloc(xhci, 1, 1, TYPE_BULK, 0, flags);
+	if (!dbc->ring_in)
+		goto in_fail;
+
+	dbc->ring_out = xhci_ring_alloc(xhci, 1, 1, TYPE_BULK, 0, flags);
+	if (!dbc->ring_out)
+		goto out_fail;
+
+	/* Allocate and populate ERST: */
+	ret = xhci_alloc_erst(xhci, dbc->ring_evt, &dbc->erst, flags);
+	if (ret)
+		goto erst_fail;
+
+	/* Allocate context data structure: */
+	dbc->ctx = xhci_alloc_container_ctx(xhci, XHCI_CTX_TYPE_DEVICE, flags);
+	if (!dbc->ctx)
+		goto ctx_fail;
+
+	/* Allocate the string table: */
+	dbc->string_size = sizeof(struct dbc_str_descs);
+	dbc->string = dbc_dma_alloc_coherent(xhci,
+					     dbc->string_size,
+					     &dbc->string_dma,
+					     flags);
+	if (!dbc->string)
+		goto string_fail;
+
+	/* Setup ERST register: */
+	writel(dbc->erst.erst_size, &dbc->regs->ersts);
+	xhci_write_64(xhci, dbc->erst.erst_dma_addr, &dbc->regs->erstba);
+	deq = xhci_trb_virt_to_dma(dbc->ring_evt->deq_seg,
+				   dbc->ring_evt->dequeue);
+	xhci_write_64(xhci, deq, &dbc->regs->erdp);
+
+	/* Setup strings and contexts: */
+	string_length = xhci_dbc_populate_strings(dbc->string);
+	xhci_dbc_init_contexts(xhci, string_length);
+
+	mmiowb();
+
+	xhci_dbc_eps_init(xhci);
+	dbc->state = DS_INITIALIZED;
+
+	return 0;
+
+string_fail:
+	xhci_free_container_ctx(xhci, dbc->ctx);
+	dbc->ctx = NULL;
+ctx_fail:
+	xhci_free_erst(xhci, &dbc->erst);
+erst_fail:
+	xhci_ring_free(xhci, dbc->ring_out);
+	dbc->ring_out = NULL;
+out_fail:
+	xhci_ring_free(xhci, dbc->ring_in);
+	dbc->ring_in = NULL;
+in_fail:
+	xhci_ring_free(xhci, dbc->ring_evt);
+	dbc->ring_evt = NULL;
+evt_fail:
+	return -ENOMEM;
+}
+
+static void xhci_dbc_mem_cleanup(struct xhci_hcd *xhci)
+{
+	struct xhci_dbc		*dbc = xhci->dbc;
+
+	if (!dbc)
+		return;
+
+	xhci_dbc_eps_exit(xhci);
+
+	if (dbc->string) {
+		dbc_dma_free_coherent(xhci,
+				      dbc->string_size,
+				      dbc->string, dbc->string_dma);
+		dbc->string = NULL;
+	}
+
+	xhci_free_container_ctx(xhci, dbc->ctx);
+	dbc->ctx = NULL;
+
+	xhci_free_erst(xhci, &dbc->erst);
+	xhci_ring_free(xhci, dbc->ring_out);
+	xhci_ring_free(xhci, dbc->ring_in);
+	xhci_ring_free(xhci, dbc->ring_evt);
+	dbc->ring_in = NULL;
+	dbc->ring_out = NULL;
+	dbc->ring_evt = NULL;
+}
+
+static int xhci_do_dbc_start(struct xhci_hcd *xhci)
+{
+	int			ret;
+	u32			ctrl;
+	struct xhci_dbc		*dbc = xhci->dbc;
+
+	if (dbc->state != DS_DISABLED)
+		return -EINVAL;
+
+	writel(0, &dbc->regs->control);
+	ret = xhci_handshake(&dbc->regs->control,
+			     DBC_CTRL_DBC_ENABLE,
+			     0, 1000);
+	if (ret)
+		return ret;
+
+	ret = xhci_dbc_mem_init(xhci, GFP_ATOMIC);
+	if (ret)
+		return ret;
+
+	ctrl = readl(&dbc->regs->control);
+	writel(ctrl | DBC_CTRL_DBC_ENABLE | DBC_CTRL_PORT_ENABLE,
+	       &dbc->regs->control);
+	ret = xhci_handshake(&dbc->regs->control,
+			     DBC_CTRL_DBC_ENABLE,
+			     DBC_CTRL_DBC_ENABLE, 1000);
+	if (ret)
+		return ret;
+
+	dbc->state = DS_ENABLED;
+
+	return 0;
+}
+
+static int xhci_do_dbc_stop(struct xhci_hcd *xhci)
+{
+	struct xhci_dbc		*dbc = xhci->dbc;
+
+	if (dbc->state == DS_DISABLED)
+		return -1;
+
+	writel(0, &dbc->regs->control);
+	dbc->state = DS_DISABLED;
+
+	return 0;
+}
+
+static int xhci_dbc_start(struct xhci_hcd *xhci)
+{
+	int			ret;
+	unsigned long		flags;
+	struct xhci_dbc		*dbc = xhci->dbc;
+
+	WARN_ON(!dbc);
+
+	pm_runtime_get_sync(xhci_to_hcd(xhci)->self.controller);
+
+	spin_lock_irqsave(&dbc->lock, flags);
+	ret = xhci_do_dbc_start(xhci);
+	spin_unlock_irqrestore(&dbc->lock, flags);
+
+	if (ret) {
+		pm_runtime_put(xhci_to_hcd(xhci)->self.controller);
+		return ret;
+	}
+
+	return mod_delayed_work(system_wq, &dbc->event_work, 1);
+}
+
+static void xhci_dbc_stop(struct xhci_hcd *xhci)
+{
+	int ret;
+	unsigned long		flags;
+	struct xhci_dbc		*dbc = xhci->dbc;
+	struct dbc_port		*port = &dbc->port;
+
+	WARN_ON(!dbc);
+
+	cancel_delayed_work_sync(&dbc->event_work);
+
+	if (port->registered)
+		xhci_dbc_tty_unregister_device(xhci);
+
+	spin_lock_irqsave(&dbc->lock, flags);
+	ret = xhci_do_dbc_stop(xhci);
+	spin_unlock_irqrestore(&dbc->lock, flags);
+
+	if (!ret) {
+		xhci_dbc_mem_cleanup(xhci);
+		pm_runtime_put_sync(xhci_to_hcd(xhci)->self.controller);
+	}
+}
+
+static void
+dbc_handle_port_status(struct xhci_hcd *xhci, union xhci_trb *event)
+{
+	u32			portsc;
+	struct xhci_dbc		*dbc = xhci->dbc;
+
+	portsc = readl(&dbc->regs->portsc);
+	if (portsc & DBC_PORTSC_CONN_CHANGE)
+		xhci_info(xhci, "DbC port connect change\n");
+
+	if (portsc & DBC_PORTSC_RESET_CHANGE)
+		xhci_info(xhci, "DbC port reset change\n");
+
+	if (portsc & DBC_PORTSC_LINK_CHANGE)
+		xhci_info(xhci, "DbC port link status change\n");
+
+	if (portsc & DBC_PORTSC_CONFIG_CHANGE)
+		xhci_info(xhci, "DbC config error change\n");
+
+	/* Port reset change bit will be cleared in other place: */
+	writel(portsc & ~DBC_PORTSC_RESET_CHANGE, &dbc->regs->portsc);
+}
+
+static void dbc_handle_xfer_event(struct xhci_hcd *xhci, union xhci_trb *event)
+{
+	struct dbc_ep		*dep;
+	struct xhci_ring	*ring;
+	int			ep_id;
+	int			status;
+	u32			comp_code;
+	size_t			remain_length;
+	struct dbc_request	*req = NULL, *r;
+
+	comp_code	= GET_COMP_CODE(le32_to_cpu(event->generic.field[2]));
+	remain_length	= EVENT_TRB_LEN(le32_to_cpu(event->generic.field[2]));
+	ep_id		= TRB_TO_EP_ID(le32_to_cpu(event->generic.field[3]));
+	dep		= (ep_id == EPID_OUT) ?
+				get_out_ep(xhci) : get_in_ep(xhci);
+	ring		= dep->ring;
+
+	switch (comp_code) {
+	case COMP_SUCCESS:
+		remain_length = 0;
+	/* FALLTHROUGH */
+	case COMP_SHORT_PACKET:
+		status = 0;
+		break;
+	case COMP_TRB_ERROR:
+	case COMP_BABBLE_DETECTED_ERROR:
+	case COMP_USB_TRANSACTION_ERROR:
+	case COMP_STALL_ERROR:
+		xhci_warn(xhci, "tx error %d detected\n", comp_code);
+		status = -comp_code;
+		break;
+	default:
+		xhci_err(xhci, "unknown tx error %d\n", comp_code);
+		status = -comp_code;
+		break;
+	}
+
+	/* Match the pending request: */
+	list_for_each_entry(r, &dep->list_pending, list_pending) {
+		if (r->trb_dma == event->trans_event.buffer) {
+			req = r;
+			break;
+		}
+	}
+
+	if (!req) {
+		xhci_warn(xhci, "no matched request\n");
+		return;
+	}
+
+	trace_xhci_dbc_handle_transfer(ring, &req->trb->generic);
+
+	ring->num_trbs_free++;
+	req->actual = req->length - remain_length;
+	xhci_dbc_giveback(req, status);
+}
+
+static enum evtreturn xhci_dbc_do_handle_events(struct xhci_dbc *dbc)
+{
+	dma_addr_t		deq;
+	struct dbc_ep		*dep;
+	union xhci_trb		*evt;
+	u32			ctrl, portsc;
+	struct xhci_hcd		*xhci = dbc->xhci;
+	bool			update_erdp = false;
+
+	/* DbC state machine: */
+	switch (dbc->state) {
+	case DS_DISABLED:
+	case DS_INITIALIZED:
+
+		return EVT_ERR;
+	case DS_ENABLED:
+		portsc = readl(&dbc->regs->portsc);
+		if (portsc & DBC_PORTSC_CONN_STATUS) {
+			dbc->state = DS_CONNECTED;
+			xhci_info(xhci, "DbC connected\n");
+		}
+
+		return EVT_DONE;
+	case DS_CONNECTED:
+		ctrl = readl(&dbc->regs->control);
+		if (ctrl & DBC_CTRL_DBC_RUN) {
+			dbc->state = DS_CONFIGURED;
+			xhci_info(xhci, "DbC configured\n");
+			portsc = readl(&dbc->regs->portsc);
+			writel(portsc, &dbc->regs->portsc);
+			return EVT_GSER;
+		}
+
+		return EVT_DONE;
+	case DS_CONFIGURED:
+		/* Handle cable unplug event: */
+		portsc = readl(&dbc->regs->portsc);
+		if (!(portsc & DBC_PORTSC_PORT_ENABLED) &&
+		    !(portsc & DBC_PORTSC_CONN_STATUS)) {
+			xhci_info(xhci, "DbC cable unplugged\n");
+			dbc->state = DS_ENABLED;
+			xhci_dbc_flush_reqests(dbc);
+
+			return EVT_DISC;
+		}
+
+		/* Handle debug port reset event: */
+		if (portsc & DBC_PORTSC_RESET_CHANGE) {
+			xhci_info(xhci, "DbC port reset\n");
+			writel(portsc, &dbc->regs->portsc);
+			dbc->state = DS_ENABLED;
+			xhci_dbc_flush_reqests(dbc);
+
+			return EVT_DISC;
+		}
+
+		/* Handle endpoint stall event: */
+		ctrl = readl(&dbc->regs->control);
+		if ((ctrl & DBC_CTRL_HALT_IN_TR) ||
+		    (ctrl & DBC_CTRL_HALT_OUT_TR)) {
+			xhci_info(xhci, "DbC Endpoint stall\n");
+			dbc->state = DS_STALLED;
+
+			if (ctrl & DBC_CTRL_HALT_IN_TR) {
+				dep = get_in_ep(xhci);
+				xhci_dbc_flush_endpoint_requests(dep);
+			}
+
+			if (ctrl & DBC_CTRL_HALT_OUT_TR) {
+				dep = get_out_ep(xhci);
+				xhci_dbc_flush_endpoint_requests(dep);
+			}
+
+			return EVT_DONE;
+		}
+
+		/* Clear DbC run change bit: */
+		if (ctrl & DBC_CTRL_DBC_RUN_CHANGE) {
+			writel(ctrl, &dbc->regs->control);
+			ctrl = readl(&dbc->regs->control);
+		}
+
+		break;
+	case DS_STALLED:
+		ctrl = readl(&dbc->regs->control);
+		if (!(ctrl & DBC_CTRL_HALT_IN_TR) &&
+		    !(ctrl & DBC_CTRL_HALT_OUT_TR) &&
+		    (ctrl & DBC_CTRL_DBC_RUN)) {
+			dbc->state = DS_CONFIGURED;
+			break;
+		}
+
+		return EVT_DONE;
+	default:
+		xhci_err(xhci, "Unknown DbC state %d\n", dbc->state);
+		break;
+	}
+
+	/* Handle the events in the event ring: */
+	evt = dbc->ring_evt->dequeue;
+	while ((le32_to_cpu(evt->event_cmd.flags) & TRB_CYCLE) ==
+			dbc->ring_evt->cycle_state) {
+		/*
+		 * Add a barrier between reading the cycle flag and any
+		 * reads of the event's flags/data below:
+		 */
+		rmb();
+
+		trace_xhci_dbc_handle_event(dbc->ring_evt, &evt->generic);
+
+		switch (le32_to_cpu(evt->event_cmd.flags) & TRB_TYPE_BITMASK) {
+		case TRB_TYPE(TRB_PORT_STATUS):
+			dbc_handle_port_status(xhci, evt);
+			break;
+		case TRB_TYPE(TRB_TRANSFER):
+			dbc_handle_xfer_event(xhci, evt);
+			break;
+		default:
+			break;
+		}
+
+		inc_deq(xhci, dbc->ring_evt);
+		evt = dbc->ring_evt->dequeue;
+		update_erdp = true;
+	}
+
+	/* Update event ring dequeue pointer: */
+	if (update_erdp) {
+		deq = xhci_trb_virt_to_dma(dbc->ring_evt->deq_seg,
+					   dbc->ring_evt->dequeue);
+		xhci_write_64(xhci, deq, &dbc->regs->erdp);
+	}
+
+	return EVT_DONE;
+}
+
+static void xhci_dbc_handle_events(struct work_struct *work)
+{
+	int			ret;
+	enum evtreturn		evtr;
+	struct xhci_dbc		*dbc;
+	unsigned long		flags;
+	struct xhci_hcd		*xhci;
+
+	dbc = container_of(to_delayed_work(work), struct xhci_dbc, event_work);
+	xhci = dbc->xhci;
+
+	spin_lock_irqsave(&dbc->lock, flags);
+	evtr = xhci_dbc_do_handle_events(dbc);
+	spin_unlock_irqrestore(&dbc->lock, flags);
+
+	switch (evtr) {
+	case EVT_GSER:
+		ret = xhci_dbc_tty_register_device(xhci);
+		if (ret) {
+			xhci_err(xhci, "failed to alloc tty device\n");
+			break;
+		}
+
+		xhci_info(xhci, "DbC now attached to /dev/ttyDBC0\n");
+		break;
+	case EVT_DISC:
+		xhci_dbc_tty_unregister_device(xhci);
+		break;
+	case EVT_DONE:
+		break;
+	default:
+		xhci_info(xhci, "stop handling dbc events\n");
+		return;
+	}
+
+	mod_delayed_work(system_wq, &dbc->event_work, 1);
+}
+
+static void xhci_do_dbc_exit(struct xhci_hcd *xhci)
+{
+	unsigned long		flags;
+
+	spin_lock_irqsave(&xhci->lock, flags);
+	kfree(xhci->dbc);
+	xhci->dbc = NULL;
+	spin_unlock_irqrestore(&xhci->lock, flags);
+}
+
+static int xhci_do_dbc_init(struct xhci_hcd *xhci)
+{
+	u32			reg;
+	struct xhci_dbc		*dbc;
+	unsigned long		flags;
+	void __iomem		*base;
+	int			dbc_cap_offs;
+
+	base = &xhci->cap_regs->hc_capbase;
+	dbc_cap_offs = xhci_find_next_ext_cap(base, 0, XHCI_EXT_CAPS_DEBUG);
+	if (!dbc_cap_offs)
+		return -ENODEV;
+
+	dbc = kzalloc(sizeof(*dbc), GFP_KERNEL);
+	if (!dbc)
+		return -ENOMEM;
+
+	dbc->regs = base + dbc_cap_offs;
+
+	/* We will avoid using DbC in xhci driver if it's in use. */
+	reg = readl(&dbc->regs->control);
+	if (reg & DBC_CTRL_DBC_ENABLE) {
+		kfree(dbc);
+		return -EBUSY;
+	}
+
+	spin_lock_irqsave(&xhci->lock, flags);
+	if (xhci->dbc) {
+		spin_unlock_irqrestore(&xhci->lock, flags);
+		kfree(dbc);
+		return -EBUSY;
+	}
+	xhci->dbc = dbc;
+	spin_unlock_irqrestore(&xhci->lock, flags);
+
+	dbc->xhci = xhci;
+	INIT_DELAYED_WORK(&dbc->event_work, xhci_dbc_handle_events);
+	spin_lock_init(&dbc->lock);
+
+	return 0;
+}
+
+static ssize_t dbc_show(struct device *dev,
+			struct device_attribute *attr,
+			char *buf)
+{
+	const char		*p;
+	struct xhci_dbc		*dbc;
+	struct xhci_hcd		*xhci;
+
+	xhci = hcd_to_xhci(dev_get_drvdata(dev));
+	dbc = xhci->dbc;
+
+	switch (dbc->state) {
+	case DS_DISABLED:
+		p = "disabled";
+		break;
+	case DS_INITIALIZED:
+		p = "initialized";
+		break;
+	case DS_ENABLED:
+		p = "enabled";
+		break;
+	case DS_CONNECTED:
+		p = "connected";
+		break;
+	case DS_CONFIGURED:
+		p = "configured";
+		break;
+	case DS_STALLED:
+		p = "stalled";
+		break;
+	default:
+		p = "unknown";
+	}
+
+	return sprintf(buf, "%s\n", p);
+}
+
+static ssize_t dbc_store(struct device *dev,
+			 struct device_attribute *attr,
+			 const char *buf, size_t count)
+{
+	struct xhci_hcd		*xhci;
+
+	xhci = hcd_to_xhci(dev_get_drvdata(dev));
+
+	if (!strncmp(buf, "enable", 6))
+		xhci_dbc_start(xhci);
+	else if (!strncmp(buf, "disable", 7))
+		xhci_dbc_stop(xhci);
+	else
+		return -EINVAL;
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(dbc);
+
+int xhci_dbc_init(struct xhci_hcd *xhci)
+{
+	int			ret;
+	struct device		*dev = xhci_to_hcd(xhci)->self.controller;
+
+	ret = xhci_do_dbc_init(xhci);
+	if (ret)
+		goto init_err3;
+
+	ret = xhci_dbc_tty_register_driver(xhci);
+	if (ret)
+		goto init_err2;
+
+	ret = device_create_file(dev, &dev_attr_dbc);
+	if (ret)
+		goto init_err1;
+
+	return 0;
+
+init_err1:
+	xhci_dbc_tty_unregister_driver();
+init_err2:
+	xhci_do_dbc_exit(xhci);
+init_err3:
+	return ret;
+}
+
+void xhci_dbc_exit(struct xhci_hcd *xhci)
+{
+	struct device		*dev = xhci_to_hcd(xhci)->self.controller;
+
+	if (!xhci->dbc)
+		return;
+
+	device_remove_file(dev, &dev_attr_dbc);
+	xhci_dbc_tty_unregister_driver();
+	xhci_dbc_stop(xhci);
+	xhci_do_dbc_exit(xhci);
+}
+
+#ifdef CONFIG_PM
+int xhci_dbc_suspend(struct xhci_hcd *xhci)
+{
+	struct xhci_dbc		*dbc = xhci->dbc;
+
+	if (!dbc)
+		return 0;
+
+	if (dbc->state == DS_CONFIGURED)
+		dbc->resume_required = 1;
+
+	xhci_dbc_stop(xhci);
+
+	return 0;
+}
+
+int xhci_dbc_resume(struct xhci_hcd *xhci)
+{
+	int			ret = 0;
+	struct xhci_dbc		*dbc = xhci->dbc;
+
+	if (!dbc)
+		return 0;
+
+	if (dbc->resume_required) {
+		dbc->resume_required = 0;
+		xhci_dbc_start(xhci);
+	}
+
+	return ret;
+}
+#endif /* CONFIG_PM */