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: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 6c7cff1..8a368d2 100644 (file)
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -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);