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SubjectRE: [PATCH v4 2/2] usb: dwc3: add debugfs node to dump FIFO/Queue available space
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> > At last, comparing with the FIFO/Queue info, I think software transfer
> > Requests list, TRBs info, EVENTs history are much more useful for
> debugging
> > the driver. If you can also add these info to each EP folder, that is awesome!
> > :)
>
> I'll think about adding these but for the lifetime of requests and trbs
> and events, etc, we have tracepoints for that. I usually do the
> following when debugging:
>
> # mount -t debugfs none /sys/kernel/debug
> # cd /sys/kernel/debug/tracing
> # echo 2048 > buffer_size_kb
> # echo 1 > events/dwc3/enable
>
> (do something to break it)
>
> # cp trace /mnt/sdcard # or something like that
>
> then read the file. You can make it as large or as small as you like
> (given some constraints, of course ;-) but I've had no issues allocating
> 128MiB in the past.
>
> --
> Balbi

Thanks for the sharing, this is a good approach to capture dynamic
behaviors. But a dump of current state has below advantages:
1. a quick view for the pending transfers. Then we can quickly
checking the transfer status.
2. no side-effect. This is important in some case. We usually
encounter some transfer issues but very hard to reproduce
it. But we cannot enable trace all the time since performance
concern. Then I thought it was so great if I can have a look for
the trb status. :)

Best Regards,
Du, Changbin

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