[ltp] Re: Linux on the T20

[linux-thinkpad@www.bm-soft.com]

Alan Shutko writes:

> It would be nice to avoid these problems.  When I asked on alsa-user
> if one could get around turning off PCI bus pm, Bill Nottingham said
> to ask IBM/Cirrus how to raise/lower the CLKRUN pin on the chip.  (I'm
> not a hardware guy, so I don't know what that means....)
>
> If that's the solution, would it be possible to get that info so some
> happy alsa hacker can fix that?  I don't know how much of a difference
> PCI bus pm makes for battery life, but I'd like to have as much pm as
> possible.
>
> Will the apm changes for the alsa-driver be contributed back to alsa?

The solution that we've provided in the preload is to massage the CLKRUN
pin programmatically. This is done via PIIX4 registers accessed via the PCI
bus. CLKRUN is a signal and protocol on the Intel PIIX4 (PCI-TO-ISA / IDE
XCELERATOR) chip set. We're had Linuxcare create an executable that
disables CLKRUN when the ALSA drivers are loaded and re-enables it when the
ALSA drivers are unloaded.

Linuxcare is releasing the ALSA driver changes back to the ALSA team. The
CLKRUN component is being released by them as well, most likely as GPL.

-- Keith

Keith Frechette
Linux Development Lead, Mobile Computing Options and Software Development
IBM Research Triangle Park, North Carolina
kfrechet@us.ibm.com / 919-543-3761 / TieLine:441-3761



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