linux-kernel - Re: [PATCH] xhci: clear port_remote

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Message-ID: <eb5d9252-1283-be73-96d6-c24a0fdf1eab@linux.intel.com>
Date:   Mon, 27 May 2019 14:16:58 +0300
From:   Mathias Nyman <mathias.nyman@...ux.intel.com>
To:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Mathias Nyman <mathias.nyman@...el.com>
Cc:     oneukum@...e.com, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xhci: clear port_remote_wakeup after resume failure

On 24.5.2019 17.52, Nicolas Saenz Julienne wrote:
> This was seen on a Dell Precision 5520 using it's WD15 dock. The dock's
> Ethernet device interfaces with the laptop through one of it's USB3
> ports. While idle, the Ethernet device and HCD are suspended by runtime
> PM, being the only device connected on the bus. Then, both are resumed on
> behalf of the Ethernet device, which has remote wake-up capabilities.
> 
> The Ethernet device was observed to randomly disconnect from the USB
> port shortly after submitting it's remote wake-up request. Probably a
> weird timing issue yet to be investigated. This causes runtime PM to
> busyloop causing some tangible CPU load. The reason is the port gets
> stuck in the middle of a remote wake-up operation, waiting for the
> device to switch to U0. This never happens, leaving "port_remote_wakeup"
> enabled, and automatically triggering a failure on any further suspend
> operation.
> 
> This patch clears "port_remote_wakeup" upon detecting a device with a
> wrong resuming port state (see Table 4-9 in 4.15.2.3). Making sure the
> above mentioned situation doesn't trigger a PM busyloop.
> 

There was a similar case where the USB3 link had transitioned to a
lower power U1 or U2 state after resume, before driver read the state,
leaving port_remote_wakeup flag uncleared.

This was fixed in 5.1 kernel by commit:

6cbcf59 xhci: Fix port resume done detection for SS ports with LPM enable

Can you check if you have it?
It should be in recent stable releases as well.

-Mathias