Re: [PATCH 4/7] cpufreq: intel_pstate: Simplify code in intel_pstate_adjust_busy_pstate

[Dirk Brandewie]

On 06/10/2014 07:51 AM, Stratos Karafotis wrote:
> On 10/06/2014 08:27 ÏÎ, Viresh Kumar wrote:
> > On 10 June 2014 02:30, Stratos Karafotis <stratosk@xxxxxxxxxxxx> wrote:
> > > Simplify the code by removing the inline functions
> > > pstate_increase and pstate_decrease and use directly the
> > > intel_pstate_set_pstate.

Doesn't apply without your scaled_busy change spin this patch with
out the scaled_busy change and explain the change more fully in the
commit message to cover Viresh's question and I am good with this change.


> > > Signed-off-by: Stratos Karafotis <stratosk@xxxxxxxxxxxx>
> > > ---
> > >   drivers/cpufreq/intel_pstate.c | 26 +++-----------------------
> > >   1 file changed, 3 insertions(+), 23 deletions(-)
> > >
> > > diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> > > index 3a49269..26a0262 100644
> > > --- a/drivers/cpufreq/intel_pstate.c
> > > +++ b/drivers/cpufreq/intel_pstate.c
> > > @@ -588,21 +588,6 @@ static void intel_pstate_set_pstate(struct cpudata *cpu, int pstate)
> > >          pstate_funcs.set(cpu, pstate);
> > >   }
> > >
> > > -static inline void intel_pstate_pstate_increase(struct cpudata *cpu, int steps)
> > > -{
> > > -       int target;
> > > -       target = cpu->pstate.current_pstate + steps;
> > > -
> > > -       intel_pstate_set_pstate(cpu, target);
> > > -}
> > > -
> > > -static inline void intel_pstate_pstate_decrease(struct cpudata *cpu, int steps)
> > > -{
> > > -       int target;
> > > -       target = cpu->pstate.current_pstate - steps;
> > > -       intel_pstate_set_pstate(cpu, target);
> > > -}
> > > -
> > >   static void intel_pstate_get_cpu_pstates(struct cpudata *cpu)
> > >   {
> > >          cpu->pstate.min_pstate = pstate_funcs.get_min();
> > > @@ -695,20 +680,15 @@ static inline void intel_pstate_calc_scaled_busy(struct cpudata *cpu)
> > >   static inline void intel_pstate_adjust_busy_pstate(struct cpudata *cpu)
> > >   {
> > >          struct _pid *pid;
> > > -       signed int ctl = 0;
> > > -       int steps;
> > > +       signed int ctl;
> > >
> > >          pid = &cpu->pid;
> > >          intel_pstate_calc_scaled_busy(cpu);
> > >
> > >          ctl = pid_calc(pid, cpu->sample.busy_scaled);
> > >
> > > -       steps = abs(ctl);
> > > -
> > > -       if (ctl < 0)
> > > -               intel_pstate_pstate_increase(cpu, steps);
> > > -       else
> > > -               intel_pstate_pstate_decrease(cpu, steps);
> > > +       /* Negative values of ctl increase the pstate and vice versa */
> > > +       intel_pstate_set_pstate(cpu, cpu->pstate.current_pstate - ctl);
> > >   }
> >
> > I am not very good at this driver but there is some obvious functional
> > change here. Earlier we used to pass
> > 'cpu->pstate.current_pstate {-|+} steps' and now you are doing '-ctl' only
>
> The original code is:	
>
> 	if (ctl < 0)
> 		intel_pstate_pstate_increase(cpu, steps);
> 	else
> 		intel_pstate_pstate_decrease(cpu, steps);
> 		
> Without inlines functions intel_pstate_pstate_increase() and
> intel_pstate_pstate_decrease() we get:
>
> 	if (ctl < 0)
> 		intel_pstate_set_pstate(cpu, cpu->pstate.current_pstate + steps);
> 	else
> 		intel_pstate_set_pstate(cpu, cpu->pstate.current_pstate - steps);
>
> 	
> But steps = abs(ctl), so:
>
> 	if (ctl < 0)
> 		intel_pstate_set_pstate(cpu, cpu->pstate.current_pstate + abs(ctl));
> 	else
> 		intel_pstate_set_pstate(cpu, cpu->pstate.current_pstate - abs(ctl));
> 	
> By definition, abs(ctl) = ctl if ctl >= 0, -ctl if ctl < 0. Thus:
>
> 	if (ctl < 0)
> 		intel_pstate_set_pstate(cpu, cpu->pstate.current_pstate + (-ctl));
> 	else
> 		intel_pstate_set_pstate(cpu, cpu->pstate.current_pstate - ctl);
>
> And:
> 	if (ctl < 0)
> 		intel_pstate_set_pstate(cpu, cpu->pstate.current_pstate - ctl);
> 	else
> 		intel_pstate_set_pstate(cpu, cpu->pstate.current_pstate - ctl);
>
> Finally remove the unnecessary if statement.		
> 	intel_pstate_set_pstate(cpu, cpu->pstate.current_pstate - ctl);
>
> So, this is equivalent with the original code.
>
> Thanks,
> Stratos
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