On Mon, 17 Apr 2006, Flynn Marquardt wrote:
> Hello,
>
> while optimizing the power consumption of my new notebook (HP TC4200) I
> discovered, that kernel version 2.6.17-rc1 needs more than 2 Watts more
> power. While tracking down the problem, I found that the new driver for
> the uhci usb host adapter seems to be the problem:
>
> Version 2.6.16.2:
> Booting into X11 login screen: 18.4 W
> after unloading uhci_hcd: 18.1 W
> Version 2.6.17-rc1:
> Booting into X11 login screen: 20.7 W
> after unloading uhci_hcd: 18.2 W
>
> The difference of 0.1W after unloading is in the tolerance of measure
> and can be ignored. The difference of 0.3 W after unloading in version
> 2.6.16.2 is common and what I measured also on other notebooks.
>
> This more than 10% more power consumption with the new driver and in my
> opinion not acceptable.
>
> In the source I saw, that the uhci driver has a new major version (3.0)
> and I think, that this is an important issue to fix, because otherwise
> version 2.6.17 would reduce the battery life for about 10% on many
> notebooks based on the Intel centrino platform.
>
> There has been a similar problem in windows, causing that the cpu cannot
> go into the deeper sleep modes because of a bug in the uhci and/or acpi
> drivers, but I do not know if this belongs to the problem here.
>
> I'm not kernel hacker and cannot solve the problem by myself but maybe
> one of you both. If you need further information or a tester for new
> patches, feel free to ask me.
It's true that there have been a lot of changes to the UHCI driver, and
one of them could cause increased power consumption under certain
circumstances. It depends on what devices are attached to the controller
and how they operate.
In your case, it would help to have more information. Here's what you
should do: Turn on USB verbose debugging in the kernel configuration
(CONFIG_USB_DEBUG). Also turn on the Debug Filesystem option in the
Kernel Hacking section (CONFIG_DEBUG_FS). Then rebuild the kernel and
load the new driver with
modprobe uhci-hcd debug=3
and also mount a debugfs filesystem, say at /sys/kernel/debug. Post the
contents of the files you find under /sys/kernel/debug/uhci.
In addition, you should post the contents of /proc/bus/usb/devices.
Depending on your distribution, /proc/bus/usb may not be mounted
automatically, so you may have to do it manually (with -t usbfs).
Alan Stern
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