Hi Matthias, thanks for the review. On Mon, 2019-05-27 at 14:16 +0300, Mathias Nyman wrote: > 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. I was aware of that patch, unfortunately it doesn't address the same issue. In my case I never get a second port status event (so no PLC == 1 or any state change seen in PLS). The device simply disconnects from the bus. I did test both the issue and fix on top of last week's master branch. Regards, Nicolas
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