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Commit 22590efb authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

intel_pstate: Avoid pointless FRAC_BITS shifts under div_fp() 



There are multiple places in intel_pstate where int_tofp() is applied
to both arguments of div_fp(), but this is pointless, because int_tofp()
simply shifts its argument to the left by FRAC_BITS which mathematically
is equivalent to multuplication by 2^FRAC_BITS, so if this is done
to both arguments of a division, the extra factors will cancel each
other during that operation anyway.

Drop the pointless int_tofp() applied to div_fp() arguments throughout
the driver.

Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 2249c00a

drivers/cpufreq/intel_pstate.c

+13 −18
Original line number Diff line number Diff line
@@ -341,17 +341,17 @@ static inline void pid_reset(struct _pid *pid, int setpoint, int busy, 


static inline void pid_p_gain_set(struct _pid *pid, int percent)

{

	pid->p_gain = div_fp(int_tofp(percent), int_tofp(100));

	pid->p_gain = div_fp(percent, 100);

}



static inline void pid_i_gain_set(struct _pid *pid, int percent)

{

	pid->i_gain = div_fp(int_tofp(percent), int_tofp(100));

	pid->i_gain = div_fp(percent, 100);

}



static inline void pid_d_gain_set(struct _pid *pid, int percent)

{

	pid->d_gain = div_fp(int_tofp(percent), int_tofp(100));

	pid->d_gain = div_fp(percent, 100);

}



static signed int pid_calc(struct _pid *pid, int32_t busy)
@@ -529,7 +529,7 @@ static ssize_t show_turbo_pct(struct kobject *kobj, 


	total = cpu->pstate.turbo_pstate - cpu->pstate.min_pstate + 1;

	no_turbo = cpu->pstate.max_pstate - cpu->pstate.min_pstate + 1;

	turbo_fp = div_fp(int_tofp(no_turbo), int_tofp(total));

	turbo_fp = div_fp(no_turbo, total);

	turbo_pct = 100 - fp_toint(mul_fp(turbo_fp, int_tofp(100)));

	return sprintf(buf, "%u\n", turbo_pct);

}
@@ -600,8 +600,7 @@ static ssize_t store_max_perf_pct(struct kobject *a, struct attribute *b, 
				   limits->max_perf_pct);

	limits->max_perf_pct = max(limits->min_perf_pct,

				   limits->max_perf_pct);

	limits->max_perf = div_fp(int_tofp(limits->max_perf_pct),

				  int_tofp(100));

	limits->max_perf = div_fp(limits->max_perf_pct, 100);



	if (hwp_active)

		intel_pstate_hwp_set_online_cpus();
@@ -625,8 +624,7 @@ static ssize_t store_min_perf_pct(struct kobject *a, struct attribute *b, 
				   limits->min_perf_pct);

	limits->min_perf_pct = min(limits->max_perf_pct,

				   limits->min_perf_pct);

	limits->min_perf = div_fp(int_tofp(limits->min_perf_pct),

				  int_tofp(100));

	limits->min_perf = div_fp(limits->min_perf_pct, 100);



	if (hwp_active)

		intel_pstate_hwp_set_online_cpus();
@@ -1011,8 +1009,8 @@ static inline void intel_pstate_calc_busy(struct cpudata *cpu) 
	struct sample *sample = &cpu->sample;

	int64_t core_pct;



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

	core_pct = div64_u64(core_pct, int_tofp(sample->mperf));

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

	core_pct = div64_u64(core_pct, sample->mperf);



	sample->core_pct_busy = (int32_t)core_pct;

}
@@ -1115,8 +1113,8 @@ static inline int32_t get_target_pstate_use_performance(struct cpudata *cpu) 
	 * specified pstate.

	 */

	core_busy = cpu->sample.core_pct_busy;

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

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

	max_pstate = cpu->pstate.max_pstate_physical;

	current_pstate = cpu->pstate.current_pstate;

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



	/*
@@ -1127,8 +1125,7 @@ static inline int32_t get_target_pstate_use_performance(struct cpudata *cpu) 
	 */

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

	if ((s64)duration_ns > pid_params.sample_rate_ns * 3) {

		sample_ratio = div_fp(int_tofp(pid_params.sample_rate_ns),

				      int_tofp(duration_ns));

		sample_ratio = div_fp(pid_params.sample_rate_ns, duration_ns);

		core_busy = mul_fp(core_busy, sample_ratio);

	}
@@ -1328,10 +1325,8 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy) 
	/* Make sure min_perf_pct <= max_perf_pct */

	limits->min_perf_pct = min(limits->max_perf_pct, limits->min_perf_pct);



	limits->min_perf = div_fp(int_tofp(limits->min_perf_pct),

				  int_tofp(100));

	limits->max_perf = div_fp(int_tofp(limits->max_perf_pct),

				  int_tofp(100));

	limits->min_perf = div_fp(limits->min_perf_pct, 100);

	limits->max_perf = div_fp(limits->max_perf_pct, 100);



 out:

	intel_pstate_set_update_util_hook(policy->cpu);