On Tue, 19 Sep 2006, David Brownell wrote:
> That's called a BUG ... firmware shouldn't have reset any device
> that the OS was managing. And in fact during true system suspend
> states, I've not heard any reports of a BIOS resetting a USB host
> controller. Do you have examples of these "many" systems??
Here are the results of tests on two of my three computers (haven't tried
the third one yet), carried out within the last 24 hours:
On my laptop, after STR the UHCI controller has been reset
(the Configured and Enter-Global-Suspend-Mode flags are 0).
This is a rather old Dell Inspiron 4000 with an Intel PIIX4
chipset.
On my desktop system at work, after STR the UHCI controllers
have been altered because PIRQDENABLE is turned on (!). This
is true for the controllers on the motherboard and for the
controllers on a VIA PCI card. The motherboard again uses
an Intel chipset (a later one than the laptop).
Based on this sample, one might conclude that the motherboard or BIOS
resets _all_ UHCI controllers during true system suspend states.
Obviously that's an overestimate. Still, I think it's true in general
that EHCI controllers tend to get treated a lot better than UHCI -- the
Rodney Dangerfield of USB host controllers. :-)
Alan Stern
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