usb over-current condition on ls1021a board

[MatthiasFuchs]

Hi,

we ran into this issue on a ls1021a based custom board. Design is very similar to the

TWR board. But without the USB 3.0 hub.

During boot the linux kernel reports an over-current condition and port power is then disabled. So no USB devices are detected:

[ 3028.127516] hub 1-0:1.0: USB hub found

[ 3028.129991] hub 1-0:1.0: 1 port detected

[ 3028.143710] hub 2-0:1.0: USB hub found

[ 3028.146156] hub 2-0:1.0: 1 port detected

[ 3028.449817] hub 1-0:1.0: over-current condition on port 1

[ 3028.669099] hub 2-0:1.0: over-current condition on port 1

The kernel comes from the SDK 1.9 with only minor changes in its configuration.

The SDHC field in the RCW is set to 3 (for DRVVBUS/PWRFAULT). Our USB power switch is connected to these pins. DRVVBUS is low and PWRFAULT is high. That's the problem.

We changed the RCW[SHDC] to 1 so that the DRVVBUS can be controlled as GPIO. As GPIO we could enable DRVVBUS, the 5V were switched on and finally USB devices were detected.

So where does this over-current condition comes from? What might cause this strange problem?

USB does also not work in u-boot. But it does on the TWR board.

Matthias

[brandensherrell]

My stock ls1043ardb reports the same over-current error on boot with no configuration changes and no usb devices connected.

[ufedor]

Please provide a log with the RDB booting and the PWRFAULT testing.

[ufedor · Accepted solution]

The LS1021A PWRFAULT is an active high signal.

Please doublecheck the design to ensure that the signal polarity of the USB power switch is also active high. If not - external inverter has to be used.