What is wrong with FreeBSD and USB Support
mrechberger at gmail.com
Mon Mar 6 11:36:59 UTC 2017
On Mon, Mar 6, 2017 at 12:30 PM, Hans Petter Selasky <hps at selasky.org> wrote:
> On 03/06/17 11:53, Markus Rechberger wrote:
>> 1. slow usb control messages - did you already noticed that?
> From what I can see no USB control transfer completed no later than 1.555
> milliseconds. I loaded the numbers in the trace into a spreadsheet and got
> the attached distribution.
> This is not slow. What times do you expect?
> The fastest XHCI can do is ~ 0.125 ms and from the analysis is appears that
> the USB device is NAKing a little bit, causing the extra delay.
it's EHCI, but the driver needs 14 seconds to load everything with
freebsd (ok there's a lot to send) but the other systems are all way
faster with that (7 seconds max for initialising 4 chipsets). I
somewhat think that this issue also has to do with the bulk latency
killing the data transfer.
Maybe the actual send is quick but maybe there's some additional
libusb20 - usb userspace interface - usb - roundtrip problem that
causes this high latency.
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