Re: [Xen-devel] cpufreq implementation for OMAP under xen hypervisor.

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

CC'ing the x86 maintainers and the cpufreq original author.


On Thu, 21 Aug 2014, Oleksandr Dmytryshyn wrote:
> Hi to all.
> 
> I'm planning to do next work:
> 
> 1. Move file xen/include/acpi/cpufreq/cpufreq.h to the
> xen/include/drivers/cpufreq/cpufreq.h
> 2. Create a new file xen/arch/x86/acpi/cpufreq/cpufreq_common.c

you can call it cpufreq.c or cpufreq_ops.c


> 3. Move some acpi-specific functions from
> xen/drivers/cpufreq/cpufreq.c to the
> xen/arch/x86/acpi/cpufreq/cpufreq_common.c:
> cpufreq_limit_change(), print_PCT(), print_PSS(), print_PSD(),
> print_PPC(), set_px_pminfo().

Why cpufreq_limit_change?


> 4. Create a new file xen/arch/arm/cpufreq/cpufreq_common.c
> 5. Functions cpufreq_add_cpu()/cpufreq_del_cpu() should be implemented
> separately for the x86 and ARM architecture (in the correspond file
> cpufreq_common.c).

Why? The implementation doesn't look x86 specific.


> 6. Port cpufreq driver for the OMAP from the Linux kernel.
> 
> In case ARM the cpufreq driver will read the settings for the
> operating-points from the device tree and the
> XENPF_set_processor_pminfo platform hypercall will not be necessary
> for ARM.
> 
> Is this the right way to implement the cpufreq for OMAP under xen hypervisor?

Yes, it's more or less what I had in mind.


> Oleksandr Dmytryshyn | Product Engineering and Development
> GlobalLogic
> M +38.067.382.2525
> www.globallogic.com
> 
> http://www.globallogic.com/email_disclaimer.txt
> 
> 
> On Tue, Aug 12, 2014 at 3:15 PM, Stefano Stabellini
> <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> > On Tue, 12 Aug 2014, Oleksandr Dmytryshyn wrote:
> >> Hi to all.
> >>
> >> I want to implement an cpufreq support for OMAP processors in xen. I
> >> use the Linux kernel as Dom0.
> >>
> >> I know that there are 2 implementations of cpufreq: Domain0 based
> >> cpufreq and Hypervisor based cpufreq. But those implementations are
> >> made only for x86 architecture, not for the ARM architecture.
> >>
> >> Could anybody give me an advise how to do that?
> >
> > I think that the best way would be to introduce cpufreq support directly
> > in the Xen hypervisor.  I would:
> >
> > 1) get cpufreq (xen/drivers/cpufreq) to build and run on ARM, with a dummy 
> > driver
> > although the cpufreq infrastructure has been written with x86 in mind,
> > it should be generalizable
> >
> > 2) write a cpufreq driver for OMAP
> 

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