Hi, Andy Shevchenko <andy.shevchenko@xxxxxxxxx> writes: > Hi! > > I have a platform with DWC3 in Dual Role mode. Currently I'm > experimenting on v5.12-rc5 with a few patches (mostly configuration) > applied [1]. I'm using Debian Unstable on the host machine and > BuildRoot with the above mentioned kernel on the target. > > **So, scenario 0: > 1. Run iperf3 -s on target > 2. Run iperf3 -c ... -t 0 on the host > 3. 0.00-10.36 sec 237 MBytes 192 Mbits/sec receiver > > **Scenario 1: > 1. Now, detach USB cable, wait for several seconds, attach it back, > repeat above: > 0.00-9.94 sec 209 MBytes 176 Mbits/sec receiver > > Note the bandwidth drop (177 vs. 192). > > (Repeating scenario 1 will give now the same result) > > **Scenario 2. > 1. Detach USB cable, attach a device, for example USB stick, > 2. See it being enumerated and detach it. > 3. Attach cable from host > 4 . 0.00-19.36 sec 315 MBytes 136 Mbits/sec receiver > > Note even more bandwidth drop! > > (Repeating scenario 1 keeps the same lower bandwidth) > > NOTE, sometimes on this scenario after several seconds the target > simply reboots (w/o any logs [from kernel] printed)! > > So, any pointers on how to debug and what can be a smoking gun here? > > Ferry reported this in [2]. There are different kernel versions and > tools to establish the connection (like connman vs. none in my case). > > [1]: https://github.com/andy-shev/linux/ > [2]: https://github.com/andy-shev/linux/issues/31 dwc3 tracepoints should give some initial hints. Look at packets sizes and period of transmission. From dwc3 side, I can't think of anything we would do to throttle the transmission, but tracepoints should tell a clearer story. -- balbi
