On Wed, 1 Jul 2015, Andy Furniss wrote: > Alan Stern wrote: > > >> Of course I disabled USB3 in bios to get ehci - is there a way with > >> bios still in this state, to force xhci again for the usb2 ports? > > > > The BIOS uses "USB3" rather imprecisely as a synonym for "xHCI". So > > you are asking if there is a way to use xHCI while telling the BIOS > > to turn xHCI off. Answer: No, there isn't. > > Ok, thanks. I assume the reverse is h/w or driver dependent? > > By which I mean that if I enable usb3 on the problem intel board I get > xhci for usb2 ports, but I notice on my desktop AMD chipset I have xhci > for usb3 ports and ehci for usb2. Yes, it depends on how the motherboard is wired up. It also can depend on which drivers are in your kernel; some computers will use EHCI for the USB-2 ports if xHCI support is configured out of the kernel. > The idea to capture the data would have been step 1 - TBH I can't think > of any other way to see if the ts packets that are missing were not > missing in the usbmon capture. > > I would need to fire up a user space app to tune/start/record the > transfer (which may have a grace period for when the tuner is adjusting > its self and producing junk/loss). > > Then when stable I would need to start full capturing with usbmon, leave > running long enough then analyse the 2 sets of data - tricky but > possible as I can use the fact that the ts packets have continuity > counters to easily detect low level loss. > > Whether or not the loss is in both "places" further analysis would be > step 2 - but I have no idea how I would match the relatively rare and > small losses with usbmon events. By comparing the arrival times of the packets. usbmon will tell you exactly which microframe an isochronous packet was scheduled for, if you understand its output. If there are any gaps in the isochronous stream, you'll be able to see them. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
