Hi Ben, Looking at this again, so bringing up this thread, although it is 4 months old.
On Tue, 12 Jun 2012 07:24:22 +1000 Benjamin Herrenschmidt <b...@kernel.crashing.org> wrote: > On Sun, 2012-06-10 at 23:31 -0400, Justin Hibbits wrote: > > > I'll settle on just getting the CPU speed change working, losing > > 333MHz on my TiBook is a few too many MHz for the poor thing to > > lose :) I do have a desktop, but that's my development platform, > > so needs to be at least somewhat stable, so my TiBook is my guinea > > pig. > > > > I've googled everything I can think of, but do you know of any > > definitive PMU documentation? Or can you give me any hints on > > what's needed just for that simple operation? > > No doco no, Darwin and Linux source code are your best bet. > > It works like sleep as in: you send the switch command and the PMU > will reboot the processor with the new frequency whenever the > processor enters NAP mode. > > This is tricky because there's a loss of cache coherency vs. ongoing > DMAs, hence tricky bits of code in there to deal with the various > caches. > > > I noticed that you wind down the ADB queue before killing the PMU. > > Is this necessary? I only disable the interrupt by writing 0x10 to > > the IER, but our interrupt model for the PMU is different from the > > Linux one. > > Well that will not disable CB1 (or the external GPIO one). You need to > make sure no other communication with the PMU takes place once you've > sent the sleep command and until you're back. > > > Is it also necessary to disable the interrupt input, even though > > the register write should be disabling the PMU's asserting of the > > line? There doesn't seem to be much more different than that, and > > setting the openpic priority, Linux sets it to 0x0f but I didn't see > > anything in OS X doing that (might that be a problem, too?) > > > > I would love to get my TiBook using the full 1GHz. > > I don't remember what openpic does in Darwin, I think interrupts are > all masked there as a side effect of the code in KeyLargo.cpp but I'm > not sure that applies to frequency changes. > > Cheers, > Ben. >From looking at the Linux PMU source, and the FreeBSD source, I can see only cosmetic differences. However, the biggest thing I see between the Linux PPC code and the FreeBSD code is that Linux quiesces Open Firmware right away. I haven't tried this with FreeBSD yet, but from your experience with development on this platform, would you think that not quiescing OFW might cause the catatonic state? - Justin _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
