actually in the BIOS there's no way to change anything related to USB. Therefore I don't know if it's the BIOS to blame or not.
However, we leave it as it is. Nobody else has ever reported any problem like this, I suspect. Seem to be my personal prob with my ACER aspire 1350. It's full of other hardware bugs anyway (even the video driver from VIA doesn't work with it...).
/Bernd
David Brownell wrote:
Alan Stern wrote:
On Sat, 7 Feb 2004, Bernd Porr wrote:
If I only load the UHCI driver all external devices get no power at all (measured with a meter).
To get power to the external bus I have to first load both drivers: ehci and uhci. When I remove the ehci driver the power is still on.
I discussed this problem with Dave a while ago and we agreed that time that we leave the problem unresolved. Maybe now it's time to fix it with this patch as well?
I recall suggesting that it was a BIOS bug, but I don't recall what options your BIOS let you control.
That sounds like it involves some weird detail of how the board manages handing off non-high-speed devices to the companion controller. For instance, maybe the PCI interface to the EHCI controller has to be enabled before the UHCI controller can access the USB bus. Or maybe power to the bus is totally under the control of the EHCI hardware and not the UHCI hardware.
"Table 4 3. Port Power Enable Control Rules" in the EHCI spec helps explain the "BIOS bug" theory. Basically, EHCI's CF bit is supposed to be cleared by device reset; and if it's cleared, then the port power switching is controlled by the companion controller. Which in this case is UHCI, which has no per-port power switching capability that we know about ... so power should be "always on".
Bernd is not seeing that behavior until the Linux EHCI code starts. Which means that either the silicon is misbehaving (power controlled by EHCI even though it's not configured) ... or the BIOS is leaving EHCI in a partially configured state: CF set, but the BIOS hasn't turned on port power (effectively disabling all USB).
- Dave
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