On Thu, 3 May 2018, Nazar Mokrynskyi wrote: > 03.05.18 22:16, Alan Stern пише: > > On Wed, 2 May 2018, Nazar Mokrynskyi wrote: > > > > As far as I know, hubs attached at boot time get initialized and > > handled in exactly the same way as hubs attached afterward. > > > > When a device is connected to a high-speed hub, the hardware in the hub > > is what determines the device's speed. Not the software in the kernel. > > The kernel just uses whatever speed the hub says to use. > > > > Have you tried a different brand of hub, to see if it makes any > > difference? > > > > Alan Stern > > > I had the same issue with different USB hub that was integrated into > monitor. It had additional power (current hub doesn't), but I don't > own that monitor anymore (I was using it when reported this issue > initially). > > There is definitely some difference, maybe related to powering USB > port at early stages of boot process, so that USB hub decides to run > devices attached to it at slower speed or something tricky like that. Or maybe it's a noise issue. > I've noticed that after boot manager (GRUB) gives control to Linux it > disconnect USB devices for a short time, but I'm not familiar with > how and why it happens. The kernel has to reset all the attached hardware, because it doesn't know what state the firmware or boot loader left the devices in. Anyway, perhaps you can work around this problem with a simple script that is set to run automatically, shortly after the system boots. The problem hub is 1-9, right? So the script needs to do this: echo 0 >/sys/bus/usb/devices/1-9/bConfigurationValue echo 1 >/sys/bus/usb/devices/1-9/bConfigurationValue That will do a soft reinit of the hub and all the devices attached to it. Hopefully the reinitialized sound card will run at high speed. 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
