Hi,
Op 30-03-2021 om 18:17 schreef Felipe Balbi:
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.
My testing (but yes, with difference kernel and network managed by
connman) shows:
1) on cold boot eem network gadget works fine
2) after unplug or warm reboot (which is also an unplug) it's broken,
speed is lost (|12.0 Mbits/sec from 200Mb/s normally)|, packets lost, no
configuration received from dhcp, occasional reboot, only way to fix is
cold boot
3) if before unplug `connmanctl disable gadget`, on replugging and
enabling it works fine
My theory is that some HW register is disturbed on a surprise unplug,
but not reset on plug or warm boot. But on cold boot is cleared. Maybe
that can help to narrow down tracepoints?
