[PATCH v2] cpufreq: cppc: Clamp default minimum limit to lowest_nonlinear_perf

[Pengjie Zhang]

The ACPI spec defines 'lowest_nonlinear_perf' as the threshold for
linear performance scaling. Performance levels below this threshold
are typically inefficient and should not be used by default.

Currently, the QoS minimum request is initialized to 0. This defaults
the performance floor to the absolute "Lowest Performance" state
instead of "lowest_nonlinear_perf", allowing the CPU to operate in
an inefficient range unnecessarily.

Signed-off-by: Pengjie Zhang <zhangpengjie2@xxxxxxxxxx>
---
Changes in v2:
  - Renamed the patch subject to better reflect the logic change.
  - Updated the commit log to clarify ACPI spec details.
Link to v1:https://lore.kernel.org/all/20260116094555.2978887-1-zhangpengjie2@xxxxxxxxxx/
---
 drivers/cpufreq/cppc_cpufreq.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index 7e8042efedd1..4a3031d9fcf4 100644
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -333,9 +333,23 @@ static unsigned int cppc_cpufreq_fast_switch(struct cpufreq_policy *policy,
 	return target_freq;
 }
 
-static int cppc_verify_policy(struct cpufreq_policy_data *policy)
+static int cppc_verify_policy(struct cpufreq_policy_data *policy_data)
 {
-	cpufreq_verify_within_cpu_limits(policy);
+	if (policy_data->min == FREQ_QOS_MIN_DEFAULT_VALUE) {
+		struct cpufreq_policy *policy __free(put_cpufreq_policy) =
+					      cpufreq_cpu_get(policy_data->cpu);
+		struct cppc_cpudata *cpu_data;
+
+		if (!policy)
+			return -EINVAL;
+
+		cpu_data = policy->driver_data;
+		policy_data->min = cppc_perf_to_khz(&cpu_data->perf_caps,
+			cpu_data->perf_caps.lowest_nonlinear_perf);
+	}
+
+	cpufreq_verify_within_cpu_limits(policy_data);
+
 	return 0;
 }
 
-- 
2.33.0