Re: EHCI driver

[Aleš Nesrsta]

Christer Weinigel píše v Út 29. 05. 2012 v 11:07 +0200:
> Hi list,
> 
> the EHCI driver in GRUB has some known problems with low-speed transfers
> and split transactions [1].  On older machines this is not a big problem
> since it's possible to connect low speed devices such a USB keyboard
> directly to a port and use the UHCI driver instead.  But modern Intel
> chipsets do not have a UHCI companion controller any more, they only
> have a EHCI controller with a normal USB 2.0 rate matching hub
> permanently connected to the EHCI port inside the chipset.
> 
> Has anybody had time to look any more at the EHCI driver?  Any ideas for
> how to fix this?

Uff, it is little bit difficult. The reason of the problem is still not
known, so it is not possible to think about solution.

I am afraid nobody has time to investigate this problem, including me,
unfortunately... - GRUB developers have lot of work on currently more
important things and I am still too busy (and there is no chance to get
more free time for me in near future).

In fact there could be probably only two reasons of the problem:
- my mistake in split transfer configuration (I checked it but who
knows...)
- GRUB "simulation" of interrupt transfer via bulk transfers is not
working when it is used via EHCI split transfers

>From my point of view it is little bit more probable the second reason.
In this case the solution could be real implementation of interrupt
transfers in GRUB - at least for EHCI. It may be possible even though
GRUB is not supporting CPU interrupts but currently I have no idea/time
to think about.

If the reason is only my mistake in EHCI code then the solution is very
simple - find the bug and correct it... :-)

If You have time and related knowledges or You know somebody like that,
You are welcome to help us - at least to find the reason of the problem
or check the EHCI split transfer code or invent implemention of
interrupt transfers in EHCI GRUB driver etc...

BR,
Ales

> 
>   /Christer
> 
> [1] http://lists.gnu.org/archive/html/grub-devel/2011-10/msg00007.html
> 
>