[bug #36740] FTDI USB Serial Device not recognized and "insmod ehci" freezes grub

[Ales Nesrsta]

Follow-up Comment #17, bug #36740 (project grub):

Hi Vladimir,

thanks to my colleague I finally have some old device with 4-port USB 1.1 hub.
Today I tested my patch published here previously - with some changes
according to actual state of related USB files in trunk. I sent actual patch
here as usb_ehci_split_130129_0.

After testing I have two news - one good and one bad:

Good:
Patch is OK - it repairs some mistake related to values needed for split
transfers, hub address and number of port where is full/low speed device
connected on the USB 2.0 hub.
So, any full/low speed device (including USB keyboard, of course) is now
working correctly if it is connected via USB 1.1 hub to USB 2.0 hub and EHCI -
at least on my PC with my hubs... :-)

Bad:
I found another very bad bug - GRUB freezes when booting Linux if USB keyboard
is used with EHCI (maybe also with UHCI/OHCI, I didn't test it yet).
The last text displayed on console is "Booting the kernel.".
If some serial console is connected to GRUB via USB/RS232 converter, the last
text on such serial console is "Loading initial ramdisk...".
I did not test what will be displayed if standard serial port will be used for
serial console.

What is very interesting for me, the freezing DOES NOT occur when USB keyboard
is connected AFTER loading EHCI driver.
And, in opposite, GRUB freezes in booting process every time if USB keyboard
is connected BEFORE loading EHCI driver (i.e., USB keyboard is handled by BIOS
until EHCI module is loaded).

And there is second potential bug (which maybe has something to do with the
first one): If USB keyboard is connected BEFORE EHCI driver is loaded, USB
keyboard is sometimes not working in GRUB until it is unplugged and plugged
again.

Maybe my testing situation is little bit special - I have connected PS2
keyboard to PC together with tested USB keyboard and I have enabled "USB
legacy support" in BIOS which means handling of USB hubs, keyboards and mass
storage devices by BIOS. (I expect problem does not happen if USB legacy
support will be disabled in BIOS - but I didn't test it yet.)

Could You try GRUB with my patch if the same situations happen also on Your
PC?

In both cases (bugs) I suspect as the reason some bad interaction between GRUB
and BIOS - maybe GRUB is using (somewhere in terminal code or elsewhere?) some
BIOS keyboard routine which becomes dead when EHCI driver is loaded - is it
possible?
(From my point of view this freezing looks little bit similarly like situation
with booting from USB disk which I was talking about in ML in thread "Boot
GRUB from USB - potential problem" in December. With big difference - the "USB
keyboard crash" happens not immediately but at the time when GRUB finishes its
work...)

Do You have some another idea(s)?
(The next suspect thing could be potentialy "grub_ehci_cancel_transfer"
routine for LOW speed device, i.e. "abnormal" removing QH from Periodic List -
I little bit don't like part of its current code, it seems to be in conflict
with EHCI specification part related to handling interrupt split transfers in
periodic list. But, if the problem will be in this function, the freezing
should occur EVERY TIME, independently if USB keyboard is connected before or
after loading of EHCI driver - so I think it is not the reason.)

BR,
Ales

(file #27349)
    _______________________________________________________

Additional Item Attachment:

File name: usb_ehci_split_130129_0        Size:6 KB


    _______________________________________________________

Reply to this item at:

  <http://savannah.gnu.org/bugs/?36740>

_______________________________________________
  Message sent via/by Savannah
  http://savannah.gnu.org/