Hi all,
I am working on the i.mx7d on Linux kernel 4.4. And I encounter some weird issue on the USB host.
I also perform the same test on the imx7d saber EVB, and the result are quite similar.
Here is my test step:
<Step 1> Connect a USB hub to the USB Host of the i.mx7d.
<Step 2> Leave the downstream ports of the USB hub unused
<Step 3> Perform plug & unplug a USB device on one downstream port of the USB hub repeatedly
<Step 4> Got error message on the Linux kernel as below:
[85384.880249] usb 1-1: USB disconnect, device number 3
[85384.885237] usb 1-1.3: USB disconnect, device number 35
[85384.894818] usb usb1-port1: cannot reset (err = -32)
[85384.904032] usb usb1-port1: cannot reset (err = -32)
[85384.912129] usb usb1-port1: cannot reset (err = -32)
[85384.919528] usb usb1-port1: cannot reset (err = -32)
[85384.925287] usb usb1-port1: cannot reset (err = -32)
[85384.930330] usb usb1-port1: Cannot enable. Maybe the USB cable is bad?
[85384.937233] usb usb1-port1: cannot reset (err = -32)
[85384.942293] usb usb1-port1: cannot reset (err = -32)
[85384.947295] usb usb1-port1: cannot reset (err = -32)
[85384.952421] usb usb1-port1: cannot reset (err = -32)
[85384.957425] usb usb1-port1: cannot reset (err = -32)
[85384.962434] usb usb1-port1: Cannot enable. Maybe the USB cable is bad?
[85384.969038] usb usb1-port1: attempt power cycle
[85385.290269] usb usb1-port1: cannot reset (err = -32)
[85385.295279] usb usb1-port1: cannot reset (err = -32)
[85385.300351] usb usb1-port1: cannot reset (err = -32)
[85385.305477] usb usb1-port1: cannot reset (err = -32)
[85385.310544] usb usb1-port1: cannot reset (err = -32)
[85385.315530] usb usb1-port1: Cannot enable. Maybe the USB cable is bad?
[85385.322216] usb usb1-port1: cannot reset (err = -32)
[85385.327441] usb usb1-port1: cannot reset (err = -32)
[85385.332515] usb usb1-port1: cannot reset (err = -32)
[85385.337518] usb usb1-port1: cannot reset (err = -32)
[85385.342582] usb usb1-port1: cannot reset (err = -32)
[85385.347554] usb usb1-port1: Cannot enable. Maybe the USB cable is bad?
[85385.354187] usb usb1-port1: unable to enumerate USB device
<Step 5> Check the USB devices on my system, and found the USB Hub disappear
<Step 6> Any connection to the USB hub downstream port would not be detected anymore
<Step 7> Reset the hub by the RESET pin or reconnect the hub(unplug/plug) would make the USB Hub connect again
I tried to trace the USB hub driver source code, the failure to reset the hub port is caused by the set_port_feature with USB_PORT_FEAT_RESET. The control message submit the urb successfully, but get EPIPE(32) after the waiting for completion.
I performed the same test on various USB hub, and the result are not totally same:
1. SMSC USB2507:
Got error as described. the USB hub disappear and need to reset the hub manually or unplug & plug manually.
2. SMSC USB2514:
Got error as described in <Step 4> but the "attempt power cycle" step works and the hub is reconnected
<Step 5>, <Step 6> & <Step 7> not happened
3. Terminus (vid:1A40, pid:0101)
Got error as described in <Step 4> but the "attempt power cycle" step works and the hub is reconnected
<Step 5>, <Step 6> & <Step 7> not happened
4. Genesys (vid:05E3, pid:0610)
no error happened
For the error message, I found an old post provide a possible workaround by setting the autosuspend timeout value to -1(disable autosuspend) to the usbcore. (fsl-ehci fsl-ehci.1: port 1 reset error -110 - Unable to connect to usb 2.0HUB). And I tried to add it to my Linux kernel command line, and it work like a charm.
I want to know more about this workaround.
1. Is there any side effect of this setting?
2. Why is this issue related to the autosuspend of the hub?
Thanks.
