USB Keyboard module reset issues [SOLVED]

Question

Hi,
Im on a fresh install of Arch, and had none of these problems on the exact same setup one day ago.
Basically my USB keyboard outputs a message to the console/dmesg every second saying: "usb 1-1.4: reset full speed USB device using ehci_hcd and address 5"
If i "rmmod ehci_hcd" then the problem stops, but this reverts my devices to USB 1.1 mode, as soon as I "modprobe ehci_hcd" again the problem persists.
Anyone got any ideas of the causes/fixes for this issue?
Ive tried moving it to a different usb port, makes no difference.
This is the latest kernel on x86_64, and I get the same problem on the Arch live/install CD. My USB keyboard has a usb2.0 hub in it as well, but on a fully up to date system yesterday I didnt have this problem. This is just a clean reinstall (with LUKS encryption added).
Thanks
Jack
Last edited by tntcoda (2009-08-30 02:19:20)

Answer 1

Hi, I am really disapointed over the lack of technical knowledge that you find these days in the internet. Linux was created first with maximum tuning capabilities. Then going mainstream they cut out all options leaving you basically helpless.
There are two problems to slow USB-performence.
1) Wrong configuration -> I assume that is not the case
2) Dumb Linux settings you can't change, because nobody tells you were to change them.
So the usual problem is, that the USB-Stick is mounted as "write-through" and not "write-back". So reading from the USB-Stick is cached, while the writing is not!!! Cache is a technique to speed things up, by not doing them in the order they appear. Especially with small files, there is no alternative. That is why modern harddisk have 8 or 16 MB cache on board. This way preformence of read/write files of size 0,005 or 0010 MB stays acceptable. USB-Sticks don't have an extra cache. The computer is supposed to take care of that.
Linux mounts USB-Sticks as "write-through", so with no caching in the writepart. So if you write many very small files, you can make a coffee break. Advantage is you can take out the stick after writing finishes without having to fear lose of data. With "write-back" you only know if the copy operation finished, that the data made it into the cache. To be sure, that the data also makes it onto the USB-Stick you need to unmount the USB-Stick.
Now everybody understands the problem. The big distributions prefer less speed rather than to have complains of Newbies that Linux corrupted their data - while the truth was, that those Newbies took out the USB-Stick without unmounting it.
So far so good, if those LINUX Expert would have left an easy accessable swith to change the "cache write policy", as windows does.
SO TO ALL THOSE LINUX EXPERT, PLEASE TELL ME WHAT I NEED TO DO TO CHANGE THE CACHE POLICY FROM WRITE-THROUGH TO WRITE-BACK. PLEEEEEEEEASE.
THX