Re: [Eas-dev] [PATCH V3 2/3] cpufreq: schedutil: Process remote callback for shared policies

[Sudeep Holla <sudeep.holla@arm.com>]

On 20/07/17 13:22, Peter Zijlstra wrote:
> On Thu, Jul 13, 2017 at 07:02:37PM -0700, Saravana Kannan wrote:
>> In all Qualcomm chipsets (well, at least the ones that have been used in
>> Android devices so far), we can switch the frequency of any CPU from any
>> other CPU. If we can do that even without fast switching, why wouldn't any
>> theoretical fast switching be incapable of supporting this? Is this a
>> limitation specific to x86 that we are assuming all architectures and
>> platforms are going to have?
> 
> So the typical implementation of fast switching we're thinking of is the
> CPU writing the DVFS request into a machine register. Now machine
> registers are typically per logical CPU.
> 

But, if ARM decides to architect and move to it to a system/machine
register, we will end up with the same limitation :( IMO.

For now with SCMI kind of interface, there's no such limitation as
yoalready mentioned in the follow up email.
-- 
Regards,
Sudeep