linux-kernel - [PATCH] cpufreq/cppc: changing highest_perf to nominal_perf in cppc_cpufreq_cpu

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Date: Sun, 28 Apr 2024 17:28:52 +0800
From: liwei <liwei728@...wei.com>
To: <rafael@...nel.org>, <viresh.kumar@...aro.org>
CC: <al.stone@...aro.org>, <ashwin.chaugule@...aro.org>,
	<linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<liwei391@...wei.com>, <liwei728@...wei.com>, <liaoyu15@...wei.com>
Subject: [PATCH] cpufreq/cppc: changing highest_perf to nominal_perf in cppc_cpufreq_cpu_init()

When turning on turbo, if frequency configuration takes effect slowly,
the updated policy->cur may be equal to the frequency configured in
governor->limits(), performance governor will not adjust the frequency,
configured frequency will remain at turbo-freq.

Simplified call stack looks as follows:
cpufreq_register_driver(&cppc_cpufreq_driver)
	...
	cppc_cpufreq_cpu_init()
		cppc_get_perf_caps()
		policy->max = cppc_perf_to_khz(caps, caps->nominal_perf)
			cppc_set_perf(highest_perf) // set highest_perf
			policy->cur = cpufreq_driver->get() // if cur == policy->max
	cpufreq_init_policy()
		...
		cpufreq_start_governor() // governor: performance
			new_freq = cpufreq_driver->get() // if new_freq == policy->max
			if (policy->cur != new_freq)
			cpufreq_out_of_sync(policy, new_freq)
				...
				policy->cur = new_freq
			...
			policy->governor->limits()
				__cpufreq_driver_target(policy->max)
					if (policy->cur==target)
					// generate error, keep set highest_perf
						ret
					cppc_set_perf(target)

Fix this by changing highest_perf to nominal_perf in cppc_cpufreq_cpu_init().

Fixes: 5477fb3bd1e8 ("ACPI / CPPC: Add a CPUFreq driver for use with CPPC")
Signed-off-by: liwei <liwei728@...wei.com>
---
 drivers/cpufreq/cppc_cpufreq.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index 64420d9cfd1e..db04a82b8a97 100644
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -669,14 +669,14 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
 	if (caps->highest_perf > caps->nominal_perf)
 		boost_supported = true;
 
-	/* Set policy->cur to max now. The governors will adjust later. */
-	policy->cur = cppc_perf_to_khz(caps, caps->highest_perf);
-	cpu_data->perf_ctrls.desired_perf =  caps->highest_perf;
+	/* Set policy->cur to norm now. */
+	policy->cur = cppc_perf_to_khz(caps, caps->nominal_perf);
+	cpu_data->perf_ctrls.desired_perf =  caps->nominal_perf;
 
 	ret = cppc_set_perf(cpu, &cpu_data->perf_ctrls);
 	if (ret) {
 		pr_debug("Err setting perf value:%d on CPU:%d. ret:%d\n",
-			 caps->highest_perf, cpu, ret);
+			 caps->nominal_perf, cpu, ret);
 		goto out;
 	}
 
-- 
2.25.1