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Re: call for help: CPU clock speed on PowerBook5,6

Hello John,

thank you for your answer.

On Sun, Mar 20, 2005 at 03:45:53PM +1030, John Steele Scott wrote:
> There is not really any proper documentation about this stuff, but
> the source code for Darwin is available on the Apple developer web
> site, so you can see exactly what they do.  The package that deals
> with this stuff used to be called AppleMacRISC2PE.
I wanted to do so, but I found out that Apple's stuff is published
under a license which is incompatible with the GPL.  Then I was
worried about tainting my brain with GPL-incompatible stuff which
would prevent me from contributing my fixes to the kernel.  Isn't this
a problem.  If I read Apple's source, see how it works, and rephrase
the result in my own "words" (well, code), would this be ok then?

> A simpler way is to find the code in your open
> firmware which knows how to change the frequency. On the iBook G4 I
> have, this is at /cpus/PowerPC,G4@0, I have set-dfs-high,
> set-dfs-low.
Sorry, no such luck for me.  The command

    find /proc/device-tree -name "*dfs*"

finds nothing.

> If you look back at the linux-ppc-dev archives from May 2004, there are some
> posts there about it. There may be some clues there.
Ok, I will have a look.  Is this list the place where I should have sent
my question?

> So far we have been assuming that the new PowerBooks behave the same
> as the older ones with the 7447A chip. If this is true, then I would
> suggest starting with a known good kernel ...
I will give this a try.

> I think what you have suggested (cpu doesn't like going high speed without
> elevated voltage) makes the most sense.
Do you know whether I can read the current voltage setting using
the following call?

    pmac_call_feature(PMAC_FTR_READ_GPIO, NULL, voltage_gpio, 0)

Would I expect the return value 5 or 1 for high voltage or does
reading not work like this.  I always get 0, even after I did

    pmac_call_feature(PMAC_FTR_WRITE_GPIO, NULL, voltage_gpio, 5)

> In one of your previous posts, you mentioned something in
> pmac_feature.c ...
Ok, I will have a look, too.

All the best and many thanks,

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