FAILED: patch "[PATCH] usb: hub: Don't try to recover devices lost during warm" failed to apply to 5.10-stable tree

[email protected]

author maintainer

2025-07-22 08:24 UTC #0 lore raw

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x 2521106fc732b0b75fd3555c689b1ed1d29d273c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025072257-ranging-salvaging-2f13@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2521106fc732b0b75fd3555c689b1ed1d29d273c Mon Sep 17 00:00:00 2001
From: Mathias Nyman <[email protected]>
Date: Mon, 23 Jun 2025 16:39:47 +0300
Subject: [PATCH] usb: hub: Don't try to recover devices lost during warm
reset.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Hub driver warm-resets ports in SS.Inactive or Compliance mode to recover a possible connected device. The port reset code correctly detects if a connection is lost during reset, but hub driver port_event() fails to take this into account in some cases. port_event() ends up using stale values and assumes there is a connected device, and will try all means to recover it, including power-cycling the port.

Details:
This case was triggered when xHC host was suspended with DbC (Debug Capability) enabled and connected. DbC turns one xHC port into a simple usb debug device, allowing debugging a system with an A-to-A USB debug cable.

xhci DbC code disables DbC when xHC is system suspended to D3, and enables it back during resume.
We essentially end up with two hosts connected to each other during suspend, and, for a short while during resume, until DbC is enabled back. The suspended xHC host notices some activity on the roothub port, but can't train the link due to being suspended, so xHC hardware sets a CAS (Cold Attach Status) flag for this port to inform xhci host driver that the port needs to be warm reset once xHC resumes.

CAS is xHCI specific, and not part of USB specification, so xhci driver tells usb core that the port has a connection and link is in compliance mode. Recovery from complinace mode is similar to CAS recovery.

xhci CAS driver support that fakes a compliance mode connection was added in commit 8bea2bd37df0 ("usb: Add support for root hub port status CAS")

Once xHCI resumes and DbC is enabled back, all activity on the xHC roothub host side port disappears. The hub driver will anyway think port has a connection and link is in compliance mode, and hub driver will try to recover it.

The port power-cycle during recovery seems to cause issues to the active DbC connection.

Fix this by clearing connect_change flag if hub_port_reset() returns -ENOTCONN, thus avoiding the whole unnecessary port recovery and initialization attempt.

Cc [email protected]

Fixes 8bea2bd37df0 ("usb: Add support for root hub port status CAS")

Tested-by Łukasz Bartosik <[email protected]>

Signed-off-by Mathias Nyman <[email protected]>

Acked-by Alan Stern <[email protected]>

Link https://lore.kernel.org/r/[email protected] open here

Signed-off-by Greg Kroah-Hartman <[email protected]>

drivers/usb/core/hub.c +6 -2

index 3e1215f7a9a0..256fe8c86828 100644
@@ -5751,6 +5751,7 @@ static void port_event(struct usb_hub *hub, int port1)
 	struct usb_device *hdev = hub->hdev;
 	u16 portstatus, portchange;
 	int i = 0;
+	int err;
 
 	connect_change = test_bit(port1, hub->change_bits);
 	clear_bit(port1, hub->event_bits);

@@ -5847,8 +5848,11 @@ static void port_event(struct usb_hub *hub, int port1)
 		} else if (!udev || !(portstatus & USB_PORT_STAT_CONNECTION)
 				|| udev->state == USB_STATE_NOTATTACHED) {
 			dev_dbg(&port_dev->dev, "do warm reset, port only\n");
-			if (hub_port_reset(hub, port1, NULL,
-					HUB_BH_RESET_TIME, true) < 0)
+			err = hub_port_reset(hub, port1, NULL,
+					     HUB_BH_RESET_TIME, true);
+			if (!udev && err == -ENOTCONN)
+				connect_change = 0;
+			else if (err < 0)
 				hub_port_disable(hub, port1, 1);
 		} else {
 			dev_dbg(&port_dev->dev, "do warm reset, full device\n");

Sasha Levin

maintainer

2025-07-22 22:50 UTC #1 lore raw

PATCH 1/2 usb: hub: avoid warm port reset during USB3 disconnect

From: Mathias Nyman <[email protected]>

[ Upstream commit f59f93cd1d720809466c7fd5aa16a236156c672b ]

During disconnect USB-3 ports often go via SS.Inactive link error state before the missing terminations are noticed, and link finally goes to RxDetect state

Avoid immediately warm-resetting ports in SS.Inactive state. Let ports settle for a while and re-read the link status a few times 20ms apart to see if the ports transitions out of SS.Inactive.

According to USB 3.x spec 7.5.2, a port in SS.Inactive should automatically check for missing far-end receiver termination every 12 ms (SSInactiveQuietTimeout)

The futile multiple warm reset retries of a disconnected device takes a lot of time, also the resetting of a removed devices has caused cases where the reset bit got stuck for a long time on xHCI roothub. This lead to issues in detecting new devices connected to the same port shortly after.

Tested-by Mark Pearson <[email protected]>

Signed-off-by Mathias Nyman <[email protected]>

Link https://lore.kernel.org/r/[email protected] open here

Signed-off-by Greg Kroah-Hartman <[email protected]>

Stable-dep-of: 2521106fc732 ("usb: hub: Don't try to recover devices lost during warm reset.")

Signed-off-by Sasha Levin <[email protected]>

---
 drivers/usb/core/hub.c | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

drivers/usb/core/hub.c +19 -5

index b88e3a5e86168..434ad066a7160 100644
@@ -2856,6 +2856,8 @@ static unsigned hub_is_wusb(struct usb_hub *hub)
 #define PORT_INIT_TRIES		4
 #endif	/* CONFIG_USB_FEW_INIT_RETRIES */
 
+#define DETECT_DISCONNECT_TRIES 5
+
 #define HUB_ROOT_RESET_TIME	60	/* times are in msec */
 #define HUB_SHORT_RESET_TIME	10
 #define HUB_BH_RESET_TIME	50

@@ -5657,6 +5659,7 @@ static void port_event(struct usb_hub *hub, int port1)
 	struct usb_device *udev = port_dev->child;
 	struct usb_device *hdev = hub->hdev;
 	u16 portstatus, portchange;
+	int i = 0;
 
 	connect_change = test_bit(port1, hub->change_bits);
 	clear_bit(port1, hub->event_bits);

@@ -5733,17 +5736,27 @@ static void port_event(struct usb_hub *hub, int port1)
 		connect_change = 1;
 
 	/*
-	 * Warm reset a USB3 protocol port if it's in
-	 * SS.Inactive state.
+	 * Avoid trying to recover a USB3 SS.Inactive port with a warm reset if
+	 * the device was disconnected. A 12ms disconnect detect timer in
+	 * SS.Inactive state transitions the port to RxDetect automatically.
+	 * SS.Inactive link error state is common during device disconnect.
 	 */
-	if (hub_port_warm_reset_required(hub, port1, portstatus)) {
-		dev_dbg(&port_dev->dev, "do warm reset\n");
-		if (!udev || !(portstatus & USB_PORT_STAT_CONNECTION)
+	while (hub_port_warm_reset_required(hub, port1, portstatus)) {
+		if ((i++ < DETECT_DISCONNECT_TRIES) && udev) {
+			u16 unused;
+
+			msleep(20);
+			hub_port_status(hub, port1, &portstatus, &unused);
+			dev_dbg(&port_dev->dev, "Wait for inactive link disconnect detect\n");
+			continue;
+		} else if (!udev || !(portstatus & USB_PORT_STAT_CONNECTION)
 				|| udev->state == USB_STATE_NOTATTACHED) {
+			dev_dbg(&port_dev->dev, "do warm reset, port only\n");
 			if (hub_port_reset(hub, port1, NULL,
 					HUB_BH_RESET_TIME, true) < 0)
 				hub_port_disable(hub, port1, 1);
 		} else {
+			dev_dbg(&port_dev->dev, "do warm reset, full device\n");
 			usb_unlock_port(port_dev);
 			usb_lock_device(udev);
 			usb_reset_device(udev);

@@ -5751,6 +5764,7 @@ static void port_event(struct usb_hub *hub, int port1)
 			usb_lock_port(port_dev);
 			connect_change = 0;
 		}
+		break;
 	}
 
 	if (connect_change)

Signature · 1 line

2.39.5

Sasha Levin

maintainer

2025-07-22 22:50 UTC #2 lore raw

PATCH 2/2 usb: hub: Don't try to recover devices lost during warm reset.

From: Mathias Nyman <[email protected]>

[ Upstream commit 2521106fc732b0b75fd3555c689b1ed1d29d273c ]