intel_pstate: Optimize calculation for max/min_perf_adj

Philippe Longepe · rafaeljw · commit a158bed5dc92 · 2016-03-11T00:04:58.000+01:00
mul_fp(int_tofp(A), B) expands to:
((A &lt;&lt; FRAC_BITS) * B) &gt;&gt; FRAC_BITS, so the same result can be obtained
via simple multiplication A * B.  Apply this observation to
max_perf * limits-&gt;max_perf and max_perf * limits-&gt;min_perf in
intel_pstate_get_min_max()."

Signed-off-by: Philippe Longepe &lt;philippe.longepe@linux.intel.com&gt;
Acked-by: Srinivas Pandruvada &lt;srinivas.pandruvada@linux.intel.com&gt;
Signed-off-by: Rafael J. Wysocki &lt;rafael.j.wysocki@intel.com&gt;
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
@@ -831,11 +831,11 @@ static void intel_pstate_get_min_max(struct cpudata *cpu, int *min, int *max)
 	 * policy, or by cpu specific default values determined through
 	 * experimentation.
 	 */
-	max_perf_adj = fp_toint(mul_fp(int_tofp(max_perf), limits->max_perf));
+	max_perf_adj = fp_toint(max_perf * limits->max_perf);
 	*max = clamp_t(int, max_perf_adj,
 			cpu->pstate.min_pstate, cpu->pstate.turbo_pstate);
 
-	min_perf = fp_toint(mul_fp(int_tofp(max_perf), limits->min_perf));
+	min_perf = fp_toint(max_perf * limits->min_perf);
 	*min = clamp_t(int, min_perf, cpu->pstate.min_pstate, max_perf);
 }
 
