Am Montag, den 10.02.2020, 17:03 +1100 schrieb Sam Lewis: > Hi, > > I have a LAN9514 (rebranded SMSC9514) USB hub which has per port > over-current protection. > > I'm using this hub within my embedded device, and I would like the hub > to continue working if any single port experiences an over-current or > short condition. > > In testing this behavior by shorting out a port, I've noticed that the > Linux USB driver continually fights against the protection in the hub > and attempts to repower the shorted port. > > Looking through the hub driver and tracing the execution flow, as far > as I can tell, this is the list of events that seem to be occurring: > > 1. I short out a single port > 2. The hub (through a power switch) detects the short and disables the port > 3. The hub sends an over-current event to the driver > 4. The driver gets the event in the `port_event` function > 5. The driver then sleeps for 100ms (for 'cool down'?) before powering > the port back on > 6. Repeat from top, until the short is removed Hi, error handling at this level has gotten little love. The basic problem is that we have no good way to switch a portback on after we have given up on it. Feel free to propose a patch to the kernel and a tool to use it and we can discuss them. Regards Oliver
