On 28.3.2019 15.41, Mathias Nyman wrote:
The issue happens when only a single hub and a single device is connected to the
USB subsystem. On my previous board, I had two USB dongles and two sound
devices connected to the same hub and it worked without issues. So I guess it
is not a real bandwidth limit. Somehow the hub seems to eat the bandwidth.
Can/will you investigate this problem further or do I have to live with it? Or
is there
anything more I can do?
This is one of the items I'm looking at.
xHC hw calculates bandwidth usage when endpoints are added based on values in
endpoint context.
The traces unfortunately didn't support this, so new tracing support was
needed, added here to my
bandwith-debug branch:
git://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git bandwidth-debug
xHC hw can also report available bandwidth, but we don't yet have driver
support.
I was planning on adding a hack that checks the available bandwidth after every
endpoint change
and add it to the testbranch, but that part is not yet finished.
New traces using the bandwidth-debug testbranch could be useful, even without the
"available bandwidth"
support
available bandwidth tracking added to bandwidth-debug branch, any chance you
could take new traces?
-Mathias
