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

[Oleksandr Dmytryshyn <oleksandr.dmytryshyn@xxxxxxxxxxxxxxx>]

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
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().
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).
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?

Oleksandr Dmytryshyn | Product Engineering and Development
GlobalLogic
M +38.067.382.2525
www.globallogic.com

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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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