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Re: USB Driver uhci.c legacy mode

From: Aleš Nesrsta
Subject: Re: USB Driver uhci.c legacy mode
Date: Sat, 24 Jul 2010 20:15:14 +0200

Hi, I am sorry to be late with answer, unfortunately, I have few time
during our school holidays...
To Your questions, chronologically:

> how would i surely know that grub usb driver would not work on this
> platform?

None of current USB drivers will work if Your PC is EHCI-only PC. One
way how to find it I described before (via lspci). But You have to be
sure You have properly set USB part in BIOS (or You should try all
possible USB BIOS configurations etc. ...).
Another way is for example to find detailed specification of Your laptop
HW. I tried shortly to find something on Internet but there are
specifications like "USB 2.0 compatible" etc. and the same
specifications are often used also for controllers which includes
OHCI/UHCI USB 1.0 too - so, I am not sure.

Definitely You can find it by check of HCSPARAMS register of EHCI.
According EHCI specification, this 32-bit register should be at USBBASE
+ 08h (USBBASE pointer should be in PCI configuration registers at PCI
base + 10h).
Bits 15:12 of HCSPARAMS should be nonzero. If You find zero there, You
have EHCI-only controller (without OHCI/UHCI companion controllers) in
Your PC, i.e., Your USB controller is currently not directly supported
by GRUB :-(

> jonatan perry wrote:
> i have another question regarding grub usb ehci support - is such
> support under development? is such support are planned to be? what is
> the current status?

Hm, I am not the right person to answer these questions properly, I am
not coordinator... Maybe Vladimir Serbinenko will answer it better.

>From my point of view:
- Development of EHCI is planned.
- Current status of EHCI driver development - probably 0%. AFAIK, nobody
is currently working on EHCI support. But I could be wrong and it can
change at any time.

I was asked some months ago by Vladimir, if I am interesting also in
EHCI. I answered "no" originally - because I thought that all EHCI
controllers have also companion OHCI/EHCI controllers and speed of USB
1.0/1.1 devices is not critical for GRUB (because it is "only"
I changed point of view from some reasons short time ago. I wanted, at
least, find why some devices are not working on my EHCI/UHCI port - it
looks like problem is on powering of ports (but UHCI has no power
control of its ports - or, at least, it is not written in UHCI
specification...). I think that this problem is maybe somewhere in EHCI,
so I want to start some experiments with EHCI.

- GRUB USB development is currently focused on enhancement and debugging
of current USB drivers and related code - for example hot-plugging and
hub support. I want to help with these things first before doing
something new (and generate new bugs...).
- EHCI is different and more complex than OHCI/UHCI
- it looks like I will too busy in next weeks/months. So, if EHCI
support will depend only on me, it will take very long time... Maybe
somebody else will start development of EHCI driver sooner (or maybe it
is started?)...?

With regards

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