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Commit c717d156 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'pm-3.15-final' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm 

Pull intel pstate fixes from Rafael Wysocki:
 "Final power management fixes for 3.15

   - Taking non-idle time into account when calculating core busy time
     was a mistake and led to a performance regression.  Since the
     problem it was supposed to address is now taken care of in a
     different way, we don't need to do it any more, so drop the
     non-idle time tracking from intel_pstate.  Dirk Brandewie.

   - Changing to fixed point math throughout the busy calculation
     introduced rounding errors that adversely affect the accuracy of
     intel_pstate's computations.  Fix from Dirk Brandewie.

   - The PID controller algorithm used by intel_pstate assumes that the
     time interval between two adjacent samples will always be the same
     which is not the case for deferable timers (used by intel_pstate)
     when the system is idle.  This leads to inaccurate predictions and
     artificially increases convergence times for the minimum P-state.
     Fix from Dirk Brandewie.

   - intel_pstate carries out computations using 32-bit variables that
     may overflow for large enough values of APERF/MPERF.  Switch to
     using 64-bit variables for computations, from Doug Smythies"

* tag 'pm-3.15-final' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  intel_pstate: Improve initial busy calculation
  intel_pstate: add sample time scaling
  intel_pstate: Correct rounding in busy calculation
  intel_pstate: Remove C0 tracking
parents 9e9a928e bf810222

drivers/cpufreq/intel_pstate.c

+31 −21
Original line number Diff line number Diff line
@@ -40,10 +40,10 @@ 
#define BYT_TURBO_VIDS		0x66d





#define FRAC_BITS 6

#define FRAC_BITS 8

#define int_tofp(X) ((int64_t)(X) << FRAC_BITS)

#define fp_toint(X) ((X) >> FRAC_BITS)

#define FP_ROUNDUP(X) ((X) += 1 << FRAC_BITS)





static inline int32_t mul_fp(int32_t x, int32_t y)

{
@@ -59,8 +59,8 @@ struct sample { 
	int32_t core_pct_busy;

	u64 aperf;

	u64 mperf;

	unsigned long long tsc;

	int freq;

	ktime_t time;

};



struct pstate_data {
@@ -98,9 +98,9 @@ struct cpudata { 
	struct vid_data vid;

	struct _pid pid;



	ktime_t last_sample_time;

	u64	prev_aperf;

	u64	prev_mperf;

	unsigned long long prev_tsc;

	struct sample sample;

};
@@ -200,7 +200,10 @@ static signed int pid_calc(struct _pid *pid, int32_t busy) 
	pid->last_err = fp_error;



	result = pterm + mul_fp(pid->integral, pid->i_gain) + dterm;



	if (result >= 0)

		result = result + (1 << (FRAC_BITS-1));

	else

		result = result - (1 << (FRAC_BITS-1));

	return (signed int)fp_toint(result);

}
@@ -560,47 +563,42 @@ static void intel_pstate_get_cpu_pstates(struct cpudata *cpu) 
static inline void intel_pstate_calc_busy(struct cpudata *cpu,

					struct sample *sample)

{

	int32_t core_pct;

	int32_t c0_pct;

	int64_t core_pct;

	int32_t rem;



	core_pct = div_fp(int_tofp((sample->aperf)),

			int_tofp((sample->mperf)));

	core_pct = mul_fp(core_pct, int_tofp(100));

	FP_ROUNDUP(core_pct);

	core_pct = int_tofp(sample->aperf) * int_tofp(100);

	core_pct = div_u64_rem(core_pct, int_tofp(sample->mperf), &rem);



	c0_pct = div_fp(int_tofp(sample->mperf), int_tofp(sample->tsc));

	if ((rem << 1) >= int_tofp(sample->mperf))

		core_pct += 1;



	sample->freq = fp_toint(

		mul_fp(int_tofp(cpu->pstate.max_pstate * 1000), core_pct));



	sample->core_pct_busy = mul_fp(core_pct, c0_pct);

	sample->core_pct_busy = (int32_t)core_pct;

}



static inline void intel_pstate_sample(struct cpudata *cpu)

{

	u64 aperf, mperf;

	unsigned long long tsc;



	rdmsrl(MSR_IA32_APERF, aperf);

	rdmsrl(MSR_IA32_MPERF, mperf);

	tsc = native_read_tsc();



	aperf = aperf >> FRAC_BITS;

	mperf = mperf >> FRAC_BITS;

	tsc = tsc >> FRAC_BITS;



	cpu->last_sample_time = cpu->sample.time;

	cpu->sample.time = ktime_get();

	cpu->sample.aperf = aperf;

	cpu->sample.mperf = mperf;

	cpu->sample.tsc = tsc;

	cpu->sample.aperf -= cpu->prev_aperf;

	cpu->sample.mperf -= cpu->prev_mperf;

	cpu->sample.tsc -= cpu->prev_tsc;



	intel_pstate_calc_busy(cpu, &cpu->sample);



	cpu->prev_aperf = aperf;

	cpu->prev_mperf = mperf;

	cpu->prev_tsc = tsc;

}



static inline void intel_pstate_set_sample_time(struct cpudata *cpu)
@@ -614,13 +612,25 @@ static inline void intel_pstate_set_sample_time(struct cpudata *cpu) 


static inline int32_t intel_pstate_get_scaled_busy(struct cpudata *cpu)

{

	int32_t core_busy, max_pstate, current_pstate;

	int32_t core_busy, max_pstate, current_pstate, sample_ratio;

	u32 duration_us;

	u32 sample_time;



	core_busy = cpu->sample.core_pct_busy;

	max_pstate = int_tofp(cpu->pstate.max_pstate);

	current_pstate = int_tofp(cpu->pstate.current_pstate);

	core_busy = mul_fp(core_busy, div_fp(max_pstate, current_pstate));

	return FP_ROUNDUP(core_busy);



	sample_time = (pid_params.sample_rate_ms  * USEC_PER_MSEC);

	duration_us = (u32) ktime_us_delta(cpu->sample.time,

					cpu->last_sample_time);

	if (duration_us > sample_time * 3) {

		sample_ratio = div_fp(int_tofp(sample_time),

				int_tofp(duration_us));

		core_busy = mul_fp(core_busy, sample_ratio);

	}



	return core_busy;

}



static inline void intel_pstate_adjust_busy_pstate(struct cpudata *cpu)