nearly-working support for cpufreq on 2004 iBook G4 with 7447A cpu

Benjamin Herrenschmidt benh at
Mon May 31 08:43:00 EST 2004

On Mon, 2004-05-31 at 00:01, John Steele Scott wrote:
> Hi all,
> I have written a patch against kernel 2.6.6 which lets the pmac cpufreq driver
> support dynamic frequency scaling on the 7447A cpu in my new iBook. It also
> fixes the incorrect clock speed reporting (i.e. on boot 2.6.6 reports cpu is
> running at 1066 MHz when really it is 533 MHz).

OF is probably not reporting wrong frrequency, check your bogomips. I
suspect your clock chip isn't configured properly at boot, like with
other newer models. I need to hack the proper bits in. I'll have a look
at this asap.

> Unfortunately, if I use this to set my cpu frequency up to 1 GHz, my system
> locks up hard when I try and do something cpu-intensive. Christiaan Welvaart
> has tested the previous version of this patch (functionally the same, but a
> bit messier), and on his system it works fine. Yet even if I use the exact
> same kernel as him, my system locks up. Both systems are 1 GHz, 12" iBooks.
> Does anyone have any ideas on why this might not work on my system? Is there
> something else that needs to be looked at when increasing the frequency after
> booting?

You might need the proper clock chip tweaks.


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