Using command "echo 1 > /sys/bus/pci/devices/0000:7a:02.0/reset" on centos7.5 system to reset xhci. On 2019/4/26 11:07, Tangnianyao (ICT) wrote: > Hi,all > > I've meet a problem about reset xhci and it may be caused by the > reset order of pci and xhci. > Using xhci-pci, when users send reset command in os(centos or red-hat os), > it would first reset PCI device by pci_reset_function. During this > process, it would disable BME(Bus Master Enable) and set BME=0, and > then enable it and set BME=1. > And then it comes to xhci reset process. First, it would send an > endpoint stop command in xhci_urb_dequeue. However, this stop ep command > fails to finish. The reason is that BME is set to 0 in former process and > xhci RUN/STOP changes to 0, and when BME is set to 1 again, RUN/STOP doesn't > recover to 1. > I've checked BME behavior in xhci spec, it shows that "If the BME bit is set to 0 > when xHC is running, the xHC may treat this as a Host Controller Error, asserting > HCE(1) and immediately halt(R/S=0 and HCH=1). Recovery from this state will > require an HCRST." It seems that the stop ep command failure is reasonable. > Maybe I've missed something and please let me know. > > linux version:5.0.0-rc3 > > Thanks, > Nianyao Tang > > > . >
