Re: [PATCH v3 1/3] cpufreq: Add boost frequency support in core

From: Viresh Kumar
Date: Tue Jun 18 2013 - 04:40:38 EST

On 18 June 2013 13:54, Lukasz Majewski <l.majewski@xxxxxxxxxxx> wrote:
> On Tue, 18 Jun 2013 08:42:13 +0200, Viresh Kumar wrote:

>> Its not about how long.. One cpu type can work longer with boost freq
>> compared to other.
>> What we probably need is:
>> - Enabled boost from sysfs if required (now below steps will come into
>> picture)
>> - See how many cpus are running, if only one then start using boost
>> freqs
> You are right here.
> I'd like to propose following solution:
> 1. For acpi (where boost_enable come into play) - do not consider
> number of active cpus (this is done in HW anyway)
> 2. For SW solution evaluate how many CPUs are running. If only one is
> running then allow enabling boost from sysfs.

Looks fine.

> But following situation is also possible: User enable boost when one
> core is only running and then for some reason other core is woken up.
> What shall be done then?
> Shall we then disable boost immediately when cpufreq detects that
> more than one core is running? Or leave this situation to be handled by
> thermal subsystem?

Obviously disable boost ASAP. Every SoC might not have a thermal
framework glue to do it.

> As a side note:
> Logic proposed at point 2, is already implemented at LAB
> (enable LAB only when one core is running and disable it when more
> than one come into play).

Hmm.. So, eventually that will go away now :)

>> - Now thermal should be come into picture to save chip in case a
>> single cpu running at boost can burn it out.
> I will extent v4 to embrace code which switches off boost at thermal.

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