When the HCD is disconnected, the DMA transfers still in-flight were cleaned-up but the count of available DMA channels (e.g. available_host_channels) was not reset. The pool of DMA channels can be depleted when doing unclean disconnection of USB peripherals, and reaches the point where no transfer was possible until the next reboot/reload of the driver. Tested by putting a programmable USB mux on the port and randomly plugging/unpluging a USB HUB with USB mass-storage key, USB-audio and USB-ethernet dongle connected to its downstream ports, and also doing the disconnection early while the devices are still enumerating to get more URBs in-flight. After the patch, the devices are still enumerating after thousands of cycles, while the port was totally dead before. Signed-off-by: Vincent Palatin <vpalatin@xxxxxxxxxxxx> --- I'm re-sending it, it seems the previous email did not show up. drivers/usb/dwc2/hcd.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c index c78c874..559b55e 100644 --- a/drivers/usb/dwc2/hcd.c +++ b/drivers/usb/dwc2/hcd.c @@ -257,6 +257,14 @@ static void dwc2_hcd_cleanup_channels(struct dwc2_hsotg *hsotg) */ channel->qh = NULL; } + /* All channels have been freed, mark them available */ + if (hsotg->core_params->uframe_sched > 0) { + hsotg->available_host_channels = + hsotg->core_params->host_channels; + } else { + hsotg->non_periodic_channels = 0; + hsotg->periodic_channels = 0; + } } /** -- 2.2.0.rc0.207.ga3a616c -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html