[U-Boot] [PATCH 1/1] USB: EHCI: Initialize multiple USB controllers at once

Wolfgang Denk wd at denx.de
Wed Jun 27 08:55:14 CEST 2012


Dear Jim Lin,

sending the very same message eight (8!) times doesnot make it a bit
more convincing - on contrary.

In message <4B9C9637D5087840A465BDCB251780E9E2D6EDA3F5 at HKMAIL02.nvidia.com> you wrote:
>
> > U-Boot is not multi-tasking, so you can always access only a single
> > USB device at a time ayway.  And it is a decoumented design principle
> > that U-Boot must not initialize any devices it does not use itself.
> > 
> > So why?
> Because of this complaint and request for devices under different controllers
> to be working at same time.

You make another claim here, but don't explain how this is supposed to
work or whay the exact use case would be where this was needed.
U-Boot will not be able to access multiple devices at the same time,
so why would it be necessary to enable these?  It should be sufficient
to enable the controller that is responsible for the single device
that is currently being used.

> "One particularly annoying consequence of this is when you use the Seaboard
> configuration on Springbank.
> Seaboard selects Tegra's USB3 as "usb 0" device, which is the one you can use,
> in order not to conflict with the flashing USB port USB1.
> However, Springbank only exposes USB1 since USB3 is used internally for the
> USB keyboard/mouse. As such, you cannot use the USB port on Springbank under
> U-Boot at the moment.
> "

I have to admit that I cannot make any sense from this statement.  The
only thing I understand is that you are trying to use a configuration
for one hardware (Seaboard) on another, incompatible hardware
(Springbank).

The simple answer to this problem is: don't do that, then.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
        Ordnung ist die Lust der Vernunft,
        aber Unordnung die Wonne der Phantasie         - Paul Claudel


More information about the U-Boot mailing list