From: You-Sheng Yang <vicamo@xxxxxxxxx> Date: Wed, 26 Feb 2020 23:37:10 +0800 > From: You-Sheng Yang <vicamo.yang@xxxxxxxxxxxxx> > > Dell USB Type C docking WD19/WD19DC attaches additional peripherals as: > > /: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/6p, 5000M > |__ Port 1: Dev 11, If 0, Class=Hub, Driver=hub/4p, 5000M > |__ Port 3: Dev 12, If 0, Class=Hub, Driver=hub/4p, 5000M > |__ Port 4: Dev 13, If 0, Class=Vendor Specific Class, > Driver=r8152, 5000M > > where usb 2-1-3 is a hub connecting all USB Type-A/C ports on the dock. > > When hotplugging such dock with additional usb devices already attached on > it, the probing process may reset usb 2.1 port, therefore r8152 ethernet > device is also reset. However, during r8152 device init there are several > for-loops that, when it's unable to retrieve hardware registers due to > being disconnected from USB, may take up to 14 seconds each in practice, > and that has to be completed before USB may re-enumerate devices on the > bus. As a result, devices attached to the dock will only be available > after nearly 1 minute after the dock was plugged in: ... > To solve this long latency another test to RTL8152_UNPLUG flag should be > added after those 20ms sleep to skip unnecessary loops, so that the device > probe can complete early and proceed to parent port reset/reprobe process. > > This can be reproduced on all kernel versions up to latest v5.6-rc2, but > after v5.5-rc7 the reproduce rate is dramatically lowered to 1/30 or less > while it was around 1/2. > > Signed-off-by: You-Sheng Yang <vicamo.yang@xxxxxxxxxxxxx> Applied, thank you.
