linux-kernel - [PATCH AUTOSEL 6.14 18/31] usb: xhci: Avoid Stop Endpoint retry loop if the endpoint seems Running

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Message-Id: <20250407181054.3177479-18-sashal@kernel.org>
Date: Mon,  7 Apr 2025 14:10:34 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Michal Pecio <michal.pecio@...il.com>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Sasha Levin <sashal@...nel.org>,
	mathias.nyman@...el.com,
	linux-usb@...r.kernel.org
Subject: [PATCH AUTOSEL 6.14 18/31] usb: xhci: Avoid Stop Endpoint retry loop if the endpoint seems Running

From: Michal Pecio <michal.pecio@...il.com>

[ Upstream commit 28a76fcc4c85dd39633fb96edb643c91820133e3 ]

Nothing prevents a broken HC from claiming that an endpoint is Running
and repeatedly rejecting Stop Endpoint with Context State Error.

Avoid infinite retries and give back cancelled TDs.

No such cases known so far, but HCs have bugs.

Signed-off-by: Michal Pecio <michal.pecio@...il.com>
Signed-off-by: Mathias Nyman <mathias.nyman@...ux.intel.com>
Link: https://lore.kernel.org/r/20250311154551.4035726-4-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/usb/host/xhci-ring.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index d3dd1ecaf6208..076c4c397ca4a 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1198,16 +1198,19 @@ static void xhci_handle_cmd_stop_ep(struct xhci_hcd *xhci, int slot_id,
 			 * Stopped state, but it will soon change to Running.
 			 *
 			 * Assume this bug on unexpected Stop Endpoint failures.
-			 * Keep retrying until the EP starts and stops again, on
-			 * chips where this is known to help. Wait for 100ms.
+			 * Keep retrying until the EP starts and stops again.
 			 */
-			if (time_is_before_jiffies(ep->stop_time + msecs_to_jiffies(100)))
-				break;
 			fallthrough;
 		case EP_STATE_RUNNING:
 			/* Race, HW handled stop ep cmd before ep was running */
 			xhci_dbg(xhci, "Stop ep completion ctx error, ctx_state %d\n",
 					GET_EP_CTX_STATE(ep_ctx));
+			/*
+			 * Don't retry forever if we guessed wrong or a defective HC never starts
+			 * the EP or says 'Running' but fails the command. We must give back TDs.
+			 */
+			if (time_is_before_jiffies(ep->stop_time + msecs_to_jiffies(100)))
+				break;
 
 			command = xhci_alloc_command(xhci, false, GFP_ATOMIC);
 			if (!command) {
-- 
2.39.5