Hello everyone. I hope this is the right place to ask such questions and I am looking forward to
your responses!
We want to use the Qualcomm RB5 as USB bridge to transmit frame data we receive over DPHY to a host PC. We are currently developing the user space application for the RB5 and are using configfs to configure the UVC gadget driver.
But we are facing some issues that might be solved, at least partly, by newer kernel versions.
So far we stick to the Linux kernel from the release branches from Linaro “release/qcomlt-x.x” and are currently using version 6.0. We apply patches for extension unit (XU) support because configfs
does not support XUs in 6.0. But with this approach we observe a very poor USB throughput of just
~90 MBit/s, measured with a USB analyzer. We also tried to use kernel version 5.15, there we did
not find patches that add XU support to configfs. With some workaround we are able to measure the
USB throughput which is very good ~4000 MBit/s! But we need the XU support in our application.
I have seen that XU support and other UVC/USB related fixes are part of kernel version 6.4, so maybe this would solve our issues. For me it looked like Linaro are currently integrating 6.4 on the branch “integration-linux-qcomlt-wip”. Does any know if they are planning to do a release that works on the RB5?
Have you perhaps also observed a similarly poor USB throughput in gadget mode and could give us a hint as to what could be wrong?
