[PATCH v2] cpufreq: CPPC: Correct desired_perf calculation

From	Hoan Tran <hotran@apm.com>
Newsgroups	linux.kernel
Subject	[PATCH v2] cpufreq: CPPC: Correct desired_perf calculation
Date	2016-10-13 19:50 +0200
Message-ID	<srSiJ-6F7-13@gated-at.bofh.it> (permalink)
Organization	linux.* mail to news gateway

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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>
---
v2
 * Return if desired_perf is the same with the old one (Prashanth's suggestion)


 drivers/cpufreq/cppc_cpufreq.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index 1b2f28f..4852d9e 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 cppc_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;
 
-- 
1.9.1

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[PATCH v2] cpufreq: CPPC: Correct desired_perf calculation Hoan Tran <hotran@apm.com> - 2016-10-13 19:50 +0200
  Re: [PATCH v2] cpufreq: CPPC: Correct desired_perf calculation "Prakash, Prashanth" <pprakash@codeaurora.org> - 2016-10-13 21:50 +0200
    Re: [PATCH v2] cpufreq: CPPC: Correct desired_perf calculation "Rafael J. Wysocki" <rafael@kernel.org> - 2016-10-13 23:20 +0200
      Re: [PATCH v2] cpufreq: CPPC: Correct desired_perf calculation Hoan Tran <hotran@apm.com> - 2016-10-13 23:30 +0200

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