On Wed, May 13, 2020 at 09:32:05PM -0400, Alan Stern wrote: > On Wed, May 13, 2020 at 04:36:20PM -0500, Bin Liu wrote: > > When a USB device attached to a hub got disconnected, MUSB controller > > generates RXCSR_RX_ERROR interrupt for the 3-strikes-out error. > > > > Currently the MUSB host driver returns -EPROTO in current URB, then the > > USB device driver could immediately resubmit the URB which causes MUSB > > generate RXCSR_RX_ERROR interrupt again. This circle causes interrupt > > storm then the hub never got a chance to report the USB device detach. > > > > To fix the interrupt storm, change the URB return code to -ESHUTDOWN for > > MUSB_RXCSR_H_ERROR interrupt, so that the USB device driver will not > > immediately resubmit the URB. > > > > Signed-off-by: Bin Liu <b-liu@xxxxxx> > > Strictly speaking, this is not the right thing to do. It goes against > the API described in error-codes.rst. A better approach would be to fix error-codes.rst says: -ESHUTDOWN The device or host controller has been disabled due to some problem that could not be worked around, such as a physical disconnect. So -ESHUTDOWN is applicable in this case - the device is disconnected behind a hub. > the drivers that immediately resubmit an URB after getting a -EPROTO This has been discussed before [1]. And John indicated there are many device drivers do not delay when resubmitting after getting -EPROTO [2], and it is quite bit of work to fix it in all device drivers [3]. So better to solve the issue in HCD. > error. After all, that is the wrong thing to do no matter what sort of > host controller the device is attached to. [1] https://www.spinics.net/lists/linux-usb/msg175292.html [2] https://www.spinics.net/lists/linux-usb/msg176327.html [3] https://www.spinics.net/lists/linux-usb/msg176375.html -Bin.
