From: Mathias Nyman <mathias.nyman@linux.intel.com>
Date: Wed, 3 Jun 2026 09:11:28 +0000 (+0300)
Subject: xhci: dbc: detect and recover hung DbC during enumeraton
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a3d34e5525cef4a53b755b94807dbe8c2976d7e7;p=thirdparty%2Fkernel%2Flinux.git

xhci: dbc: detect and recover hung DbC during enumeraton

Add a timeout between the detection of the debug host connection and
the DbC Run transition to ‘1’. Toggle the DCE bit to re-enable DbC in
order to retry the debug device enumeration process if the DbC run
transition takes too long.

Set the timeout to 2 seconds

See xhci specification section 7.6.4.1 "Debug Capability Initialization"

Also detect cable disconnect during enable and connected state.

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://patch.msgid.link/20260603091132.1110849-12-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/usb/host/xhci-dbgcap.c b/drivers/usb/host/xhci-dbgcap.c
index 34441ffa5e15..b1cabf5582fa 100644
--- a/drivers/usb/host/xhci-dbgcap.c
+++ b/drivers/usb/host/xhci-dbgcap.c
@@ -901,23 +901,49 @@ static enum evtreturn xhci_dbc_do_handle_events(struct xhci_dbc *dbc)
 		return EVT_ERR;
 	case DS_ENABLED:
 		portsc = readl(&dbc->regs->portsc);
+		ctrl = readl(&dbc->regs->control);
+
 		if (portsc & DBC_PORTSC_CONN_STATUS) {
 			xhci_dbc_set_state(dbc, DS_CONNECTED);
 			dev_info(dbc->dev, "DbC connected\n");
+		} else if (!(ctrl & DBC_CTRL_DBC_ENABLE)) {
+			dev_err(dbc->dev, "unexpected DbC disable, xHC reset?\n");
 		}
 
 		return EVT_DONE;
 	case DS_CONNECTED:
 		ctrl = readl(&dbc->regs->control);
+		portsc = readl(&dbc->regs->portsc);
 		if (ctrl & DBC_CTRL_DBC_RUN) {
 			xhci_dbc_set_state(dbc, DS_CONFIGURED);
 			dev_info(dbc->dev, "DbC configured\n");
-			portsc = readl(&dbc->regs->portsc);
 			writel(portsc, &dbc->regs->portsc);
 			ret = EVT_GSER;
 			break;
 		}
 
+		/* Connection lost */
+		if (!(portsc & DBC_PORTSC_CONN_STATUS)) {
+			/* covers DCE == 0 as it also sets CONN_STATUS to 0 */
+			dev_warn(dbc->dev, "DbC connection lost mid enumeration\n");
+			xhci_dbc_set_state(dbc, DS_ENABLED);
+
+			return EVT_DONE;
+		}
+
+		/* Enumeration timeout */
+		if (time_is_before_jiffies(dbc->state_timestamp +
+				msecs_to_jiffies(DBC_ENUMERATION_TIMEOUT))) {
+			dev_err(dbc->dev, "DbC enumeration timeout, re-enabling DbC\n");
+			dev_dbg(dbc->dev, "dcctrl %x, dcportsc %x\n", ctrl, portsc);
+
+			/* Toggle DCE to retry enumeration */
+			ret = xhci_dbc_enable_dce(dbc, false);
+			udelay(100);
+			ret = xhci_dbc_enable_dce(dbc, true);
+			xhci_dbc_set_state(dbc, DS_ENABLED);
+		}
+
 		return EVT_DONE;
 	case DS_CONFIGURED:
 		/* Handle cable unplug event: */
diff --git a/drivers/usb/host/xhci-dbgcap.h b/drivers/usb/host/xhci-dbgcap.h
index b3efea43a6be..df7aca8bfe99 100644
--- a/drivers/usb/host/xhci-dbgcap.h
+++ b/drivers/usb/host/xhci-dbgcap.h
@@ -113,6 +113,7 @@ struct dbc_ep {
 #define DBC_POLL_INTERVAL_DEFAULT	64	/* milliseconds */
 #define DBC_POLL_INTERVAL_MAX		5000	/* milliseconds */
 #define DBC_XFER_INACTIVITY_TIMEOUT	10	/* milliseconds */
+#define DBC_ENUMERATION_TIMEOUT		2000	/* milliseconds */
 /*
  * Private structure for DbC hardware state:
  */