linux-kernel - [PATCH net-next 1/2] r8152: If inaccessible at resume time, issue a reset

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Date: Mon, 20 May 2024 13:41:11 -0700
From: Douglas Anderson <dianders@...omium.org>
To: "David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Hayes Wang <hayeswang@...ltek.com>
Cc: danielgeorgem@...gle.com,
	Douglas Anderson <dianders@...omium.org>,
	Andrew Lunn <andrew@...n.ch>,
	Grant Grundler <grundler@...omium.org>,
	Heiner Kallweit <hkallweit1@...il.com>,
	linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org,
	netdev@...r.kernel.org
Subject: [PATCH net-next 1/2] r8152: If inaccessible at resume time, issue a reset

If we happened to get a USB transfer error during the transition to
suspend then the usb_queue_reset_device() that r8152_control_msg()
calls will get dropped on the floor. This is because
usb_lock_device_for_reset() (which usb_queue_reset_device() uses)
silently fails if it's called when a device is suspended or if too
much time passes.

Let's resolve this by resetting the device ourselves in r8152's
resume() function.

NOTE: due to timing, it's _possible_ that we could end up with two USB
resets: the one queued previously and the one called from the resume()
patch. This didn't happen in test cases I ran, though it's conceivably
possible. We can't easily know if this happened since
usb_queue_reset_device() can just silently drop the reset request. In
any case, it's not expected that this is a problem since the two
resets can't run at the same time (because of the device lock) and it
should be OK to reset the device twice. If somehow the double-reset
causes problems we could prevent resets from being queued up while
suspend is running.

Signed-off-by: Douglas Anderson <dianders@...omium.org>
---

 drivers/net/usb/r8152.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index 19df1cd9f072..6a3f4b2114ee 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -8554,6 +8554,19 @@ static int rtl8152_system_resume(struct r8152 *tp)
 		usb_submit_urb(tp->intr_urb, GFP_NOIO);
 	}

+	/* If the device is RTL8152_INACCESSIBLE here then we should do a
+	 * reset. This is important because the usb_lock_device_for_reset()
+	 * that happens as a result of usb_queue_reset_device() will silently
+	 * fail if the device was suspended or if too much time passed.
+	 *
+	 * NOTE: The device is locked here so we can directly do the reset.
+	 * We don't need usb_lock_device_for_reset() because that's just a
+	 * wrapper over device_lock() and device_resume() (which calls us)
+	 * does that for us.
+	 */
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
+		usb_reset_device(tp->udev);
+
 	return 0;
 }

-- 
2.45.0.rc1.225.g2a3ae87e7f-goog