Re: USB D3 vs system S3

[Carlos Corbacho <carlos@strangeworlds.co.uk>]

On Wednesday 09 January 2008 00:09:21 Carlos Corbacho wrote:
> 2) Based on poking around in Vista, it may also be required to disable
> autosuspend for OHCI on CK804 (nForce 4), since Vista here apparently does
> not enable USB autosuspend on the USB hubs on this board (yet enabling
> autosuspend is supposedly the default Vista behaviour, and I've certainly
> never touched the USB settings in Vista).
>
> Given we have two different BIOS's from different manufacturers for the
> same chipset, that both have a similar SMI trap, and are both breaking
> here, I wonder if this is a known problem with the reference nVidia BIOS;
> so Windows will not put USB devices into D3 early on this chipset, to
> ensure that USB0 is not in a low power state before _PTS() is called
> (unfortunately, on point 2, I don't have enough to back it up either way,
> besides my own observations here).

I've had confirmation from another nForce 4 box that Vista also disables 
autosuspend/ selective suspend on the root hubs there, so I'm pretty 
confident in saying now that this will also be needed in Linux (definitely 
for OHCI. I don't think we need to stop autosuspend on EHCI, even though 
Windows does appear to disable it for that as well), to avoid inadvertently 
triggering the suspend-to-RAM hang on these broken BIOSs.

(Testing also shows that putting the OHCI controller into D2 is no good 
either - having it in any state other than D1 before we call the ACPI _PTS() 
method will reliably hang the box on suspend).

What's the best way to go about doing this? I've been glancing over the OHCI 
code and I can't see how to easily do this (unless 'broken_suspend' is the 
correct option here?)

-Carlos
-- 
E-Mail: carlos@strangeworlds.co.uk
Web: strangeworlds.co.uk
GPG Key ID: 0x23EE722D