Re: USB Driver uhci.c legacy mode

[jonatan perry]

hello ales,
thank you so much for you detailed answers!
how would i surely know that grub usb driver would not work on this platform?

On Mon, Jul 5, 2010 at 10:58 PM, Aleš Nesrsta <address@hidden> wrote:

jonatan perry wrote:
> Hello Ales,
> Unfortunately, the discussed platform (Lenovo t410 laptop) includes no
> UHCI controller along with the EHCI, as well no BIOS USB 1.0 (UHCI)
> legacy support.
> as I understand from the EHCI specs there are several legacy
> registers, named USBLEGSUP and USBLEGCTLSTS, can I assists those
> registers in order to achieve legacy support?
> I didn't found any source code examples nor additional documentation
> regarding those registers.
>
> any help would be most welcome.

Hi,

in this case it looks like You unfortunately cannot use USB devices with
GRUB2 because GRUB2 does not support EHCI controllers yet.

Short and simplified overview - to clarify some things/words/terms:

- GRUB2 currently supports OHCI and UHCI USB controllers only (these
controllers support USB 1.1 devices only - "low speed" and "full
speed").

- EHCI is another kind of USB controller than UHCI or OHCI - it supports
USB 2.0 devices only ("high speed"). Unfortunately, GRUB2 currently does
not have driver module for EHCI.

- According to UHCI/OHCI/EHCI specification, "legacy support" means HW
emulation of USB mouse&keyboard as PS/2 devices. I.e., USB mouse or
keyboard looks like connected via PS/2 port. It is useful for BIOS,
bootloaders and some other software (like old DOS) which does not have
its own USB support.

- Some BIOSes (for example on my computer...) mean by "legacy support"
also booting from USB. In this case is connected USB disk "emulated" as
HD (or FD) by BIOS. Such kind of booting should work also with GRUB2 and
You don't need to use uhci/ohci module.

- "Legacy support" DOES NOT (or, better, should not) mean support of
USB1.1 devices, i.e., You cannot "switch" EHCI to UHCI (or OHCI) via
"legacy support". The only one possible way is to add EHCI support into
GRUB2 (new driver module).

- USB 2.0 devices (USB disks etc.) are mostly backwards compatible, i.e.
they are working also when connected to OHCI/UHCI controllers.

Regards
Ales

>
> On Mon, Jul 5, 2010 at 8:14 PM, Aleš Nesrsta <address@hidden> wrote:
>         > On 07/02/2010 12:30 PM, jonatan perry wrote:
>         > > Hi all,
>         > > I am using grub2 uhci.c usb driver for testing new
>         hardware, on some
>         > > occuisions the UHCI signature test fails (can be found on
>         the PCI
>         > > iteration routine), the driver thest if the controller
>         founded by PCI
>         > > has a signature as uhci should have (0x0c0300), on some of
>         my new
>         > > hardwares the signature is as EHCI (usb 2.0) means
>         0x0c0302, if i
>         > > change the signature that the driver searches the rest of
>         the driver
>         > > fails, probably because i need to activate a legacy bit in
>         the
>         > > configuration register in the EHCI Controller.
>         > EHCI is never alone. It must always have a companion
>         controller (UHCI or
>         > OHCI). Also be sure to use either bzr trunk or usb branch.
>
>
>         Note:
>         Unfortunately, according to specification, EHCI can be
>         installed alone
>         (without companion UHCI or OHCI controller(s)) but it is
>         probably very
>         rare computer HW configuration.
>         Try command "lspci" in Linux and search for lines with "USB
>         Controller"
>         - if You will find EHCI only, You really have "EHCI only"
>         computer.
>         But You can have some bad BIOS setting (You should enable USB
>         1.1
>         controller(s) in BIOS.).
>
>
>         > > i have searched EHCI Specs for legacy mode and could not
>         understand
>         > > how to configure legacy mode... and i hope some of you guy
>         could help me.
>         > >
>         > > thanks!
>         > >
>         > >
>         > > _______________________________________________
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>         > >
>         >
>         >
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