On 12/8/2016 2:43 PM, John Stultz wrote: > On Tue, Dec 6, 2016 at 7:52 PM, John Youn <John.Youn@xxxxxxxxxxxx> wrote: >> On 12/6/2016 5:48 PM, John Stultz wrote: >>> Hey John, >>> Just wanted to send this by you, as it seems something is >>> slightly off with the GOTGCTL state when removing a otg adapter >>> cable. The following seems to work around the issue I'm seeing. >>> >>> >>> When removing a USB-A to USB-otg adapter cable, we get a change >>> status irq, and then in dwc2_conn_id_status_change, we >>> erroniously see the GOTGCTL_CONID_B flag set. This causes us to >> >> This is the correct behavior for an OTG controller. When you unplug a >> cable or plug in the B end of a cable, the ID pin floats, indicating >> it is a B-Device. >> >> When you plug in an A-cable, which is what your adapter is, it will >> ground the pin, meaning A-device. > > Hrm... So normally, when I plug in the gadget cable into the OTG port, > I see the change_status irq comes in and the function sees: > > dwc2 f72c0000.usb: gotgctl=4010000 > dwc2 f72c0000.usb: gotgctl.b.conidsts=1 > dwc2 f72c0000.usb: Do port resume before switching to device mode > dwc2 f72c0000.usb: dwc2_hsotg_enqueue_setup: failed queue (-11) > dwc2 f72c0000.usb: new device is high-speed > dwc2 f72c0000.usb: new device is high-speed > dwc2 f72c0000.usb: new device is high-speed > dwc2 f72c0000.usb: new address 37 > configfs-gadget gadget: high-speed config #1: b > > Then when I unplug the cable: > > dwc2 f72c0000.usb: gotgctl=2200000 > dwc2 f72c0000.usb: gotgctl.b.conidsts=0 > usb 1-1: reset high-speed USB device number 13 using dwc2 > > > > When I plug in the OTG to USB-A adapter cable w/ a mouse plugged in > (note I see no change interrupt): > > usb 1-1: USB disconnect, device number 13 > usb 1-1: new low-speed USB device number 14 using dwc2 > input: Logitech USB Optical Mouse as > /devices/platform/soc/f72c0000.usb/usb1/1-1/1-1:1.0/0003:046D:C058.0003/input/input3 > hid-generic 0003:046D:C058.0003: input,hidraw0: USB HID v1.11 Mouse > [Logitech USB Optical Mouse] on usb-f72c0000.usb-1/input0 > > > Then unplugging the OTG to USB-A adapter cable w/ mouse: > > dwc2 f72c0000.usb: gotgctl=4010000 > dwc2 f72c0000.usb: gotgctl.b.conidsts=1 > dwc2 f72c0000.usb: Do port resume before switching to device mode > dwc2 f72c0000.usb: Waiting for Peripheral Mode, Mode=Host > > <here we get stuck in the loop until it finishes, unless using the > patch from this thread> > > usb 1-1: USB disconnect, device number 14 > dwc2 f72c0000.usb: gotgctl=2200000 > dwc2 f72c0000.usb: gotgctl.b.conidsts=0 > usb 1-1: new high-speed USB device number 15 using dwc2 > hub 1-1:1.0: USB hub found > hub 1-1:1.0: 3 ports detected > > > So I only get the change irq when: > * I plug in a micro-usb-B cable for gadget mode > * I remove the micro-usb-B cable being used for gadget mode > * I remove a OTG to USB-A adapter > That's very strange. It's opposite of how it's supposed to work. > One slight quirk, is that I don't always see the change irq when > removing the OTG to USB, as if I plug in a highspeed mass-storage > device, instead of the low-speed mouse, I don't see the change > interrupt and the device shows up and disappears the same as when I > plug into the normal USB-A host ports on the board. > > >>> get stuck in the "while (!dwc2_is_device_mode(hsotg))" loop, >>> spitting out "Waiting for Peripheral Mode, Mode=Host" warnings >>> until it fails out many seconds later. >> >> This is weird. Once the ID pin goes to B, the core should become a >> peripheral and this should be reflected in the status registers. >> >>> >>> This patch works around the issue by re-reading the GOTGCTL >>> state to check if the GOTGCTL_CONID_B is still set and if not >>> restarting the change status logic. >> >> This also seems weird. The connector id status shouldn't go back to A, >> assuming you've left the cable unplugged. > > So I suspect this has something to do with the way the USB-A host > ports on the board are wired up. As removing the usb-b plug seems to > switch the device back into A mode. > > One quirk with this board is that the USB-A ports on the board do not > function if anything is in the OTG/B plug (which is frustrating to use > at times). > Do you mean there are multiple A-ports on the board hooked up to the same controller? If so, that would go a long way towards explaining things. Because the hsotg is a single-port OTG controller. If there are multiple A-ports, that means a hub has to be hard-wired internally to the port. But if that's the case the OTG function won't work because OTG doesn't work through a hub. It must go directly to the otg port. So there must be some external logic kicking-in to switch routing to the OTG port or to the HUB. This would explain this behavior with the ID pin status. Since hooking up the HUB would make the controller an A-device whereas normally it would be a B-device. > Guodong or Chen Yu understand the hardware details a bit better, and > might be able to explain more if you need more information. > Yeah it would be good to get some insight into this from a hardware point of view. Regards, John -- 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
