Re: [PATCH v2 1/3] cpufreq:boost: CPU frequency boost codeunification for software and hardware solutions

[Viresh Kumar]

On 12 June 2013 14:39, Lukasz Majewski <l.majewski@xxxxxxxxxxx> wrote:
> On Wed, 12 Jun 2013 13:39:18 +0530, Viresh Kumar wrote:
>> On 12 June 2013 13:09, Lukasz Majewski <l.majewski@xxxxxxxxxxx> wrote:

>> You don't have to add an extra "---" line. Just write your changelog
>> after "---" added by git and give a blank line between your last
>> changelog line and below ones (probably just to make it more
>> readable and not a must, but i am not sure).
>
> I got your point. If you prefer, I will stick to it. No problem.

Its not how I prefer it, but how everybody does it :)

> As a side note:
>
> In the other open source project (u-boot) we use the pattern which I've
> used previously. It has one big advantage - I can edit change log at
> git gui (just below sign-of-by). It is simply more convenient for
> me :-). Those changes between "---" are simply skipped by git am
> afterwards.

Yes, I am still asking you to follow the same steps:

git send-email --annotate ***patches***

and then write whatever you don't want to be logged by git am after
the "---" already present in the patch.

>> >> >  drivers/cpufreq/cpufreq.c    |   69
>> >> > ++++++++++++++++++++++++++++++++++++++++++
>> >> > drivers/cpufreq/freq_table.c |   57
>> >> > ++++++++++++++++++++++++++++++++-- include/linux/cpufreq.h      |
>> >> > 12 ++++++++ 3 files changed, 136 insertions(+), 2 deletions(-)
>>
>> > I think that we shall give users some flexibility and don't assume
>> > that low_level_boost is only used for one solution/vendor.
>> >
>> > It is also needed with software controlled boost. Please refer to
>> > patch 3/3.
>>
>> You didn't get me. I am not asking to keep it only for Intel. But keep
>> this variable as is (s/low_level_boost/set_boost_freq), and make it
>> optional. So, few drivers can implement it but not everybody is
>> required to.
>
> The low_level_boost (set_boost_freq)[*] is optional. However it seems to
> me, that the burden of changing available set of frequencies (when
> boost is enabled) must be put to cpufreq driver anyway.

Driver shouldn't play with boost freqs at runtime. This has to be handled
by cpufreq core. The only thing cpufreq driver must be doing in
low_level_boost or set_boost_freq (as what I suggested it to be), is
to set the boost frequency requested by core. And so this routine would
only be defined by drivers that have a special way of setting boost
frequencies. For others ->target() routine should be able to set all
freqs, boost or non boost.

> Without this function [*] defined, we cannot enable frequency boosting.

why?

>> So, Add another variable: boost_supported, which will tell cpufreq
>> core that boost is supported by governor or not.
>                                   ^^^^^^^shouldn't it be cpufreq driver?

Yeah, sorry :(

> Ok, boost_supported seems needed. In my opinion it shall be defined at
> cpufreq_driver structure (since it provides boosting infrastructure
> anyway).

that's what I asked.

>> And a global variable in cpufreq.c boost_enabled to track status of
>> what user has requested.
>
> I think, that boost_enable shall be also defined at cpufreq driver (as
> proposed in the patch).

Not really. Driver should only care about if it supports boost or not.
If it is enabled/disabled by sysfs or not should be kept inside core
in a global variable.

Moreover, if we have 5-6 cpufreq drivers compiled in (for multi-arch
compiled kernels), we will save memory wasted by this variable if
it is present in cpufreq_driver.

> Moreover, boost_enable flag is already defined at
> acpi-cpufreq.c (as static). We will have two flags for the same
> purpose.

No, we don't have to. Just expose another API from cpufreq core
to get status of boost.

> So we want as follows:
> show_boost = 1 ---> show only frequencies tagged as CPUFREQ_BOOST_FREQ
> show_boost = 0 ---> show only "normal" (non boost) frequencies

Yes.

>> You are just talking about showing boost freqs in sysfs. I am talking
>> about the frequencies that governors will select when boost is
>> disabled from sysfs. Because we don't skip boost frequencies in
>> target() routines, we will set them as and when governor requests
>> them.
>
> I think, that it is the main issue here and it shall be cleared out:
>
> Frequencies marked as: CPUFREQ_BOOST_FREQ are added permanently to the
> freq_table.
> That is the distinction to the original overclocking patch posted with
>> LAB, where freq_boost structure was modified and boost frequencies were
> either valid or invalid.

Yes.

> Then we can in SW control boost in two ways:
> 1. change policy->max value (to the maximal boost frequency) - as it is
> done now (v3) at Exynos. This is the simple solution (patch 3/3)

Drivers aren't supposed to set policy->max. It should be taken care
of by core or freq_table.c file.

> 2. Modify all freq_table helper functions to be aware of boost and
> skip boost frequencies when boost_enable = 0. (as it was done at v2).
> This requires code modification at freq_table.c and reevaluation of
> policy.

Yes, the core must be aware of it and must take the right decision
here. So, we need to take care of boost freq in freq_table.c
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