cpufreq: CPPC: Correct desired_perf calculation

The desired_perf is an abstract performance number. Its value should
be in the range of [lowest perf, highest perf] of CPPC.
The correct calculation is
  desired_perf = freq * cppc_highest_perf / cppc_dmi_max_khz

And cppc_cpufreq_set_target() returns if desired_perf is exactly
the same with the old perf.

Signed-off-by: Hoan Tran <hotran@apm.com>
Reviewed-by: Prashanth Prakash <pprakash@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index 99db4227ae38..f7e98fc077c1 100644
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -80,11 +80,17 @@ static int cppc_cpufreq_set_target(struct cpufreq_policy *policy,
 {
         struct cpudata *cpu;
         struct cpufreq_freqs freqs;
+        u32 desired_perf;
         int ret = 0;
 
         cpu = all_cpu_data[policy->cpu];
 
-        cpu->perf_ctrls.desired_perf = (u64)target_freq * policy->max / cppc_dmi_max_khz;
+        desired_perf = (u64)target_freq * cpu->perf_caps.highest_perf / cppc_dmi_max_khz;
+        /* Return if it is exactly the same perf */
+        if (desired_perf == cpu->perf_ctrls.desired_perf)
+                return ret;
+
+        cpu->perf_ctrls.desired_perf = desired_perf;
         freqs.old = policy->cur;
         freqs.new = target_freq;