[PATCH v4 1/3] cpufreq: cppc: Add update_limits support for Highest Performance changes

[Xueqin Luo]

ACPI CPPC specification requires OSPM to re-evaluate the Highest
Performance register when Notify(0x85) is received for a processor
device.

Implement cppc_cpufreq_update_limits() to refresh the cached
highest_perf capability through cppc_get_highest_perf() and update
policy->cpuinfo.max_freq accordingly. Use refresh_frequency_limits()
to let the cpufreq core update policy->max via the standard
cpufreq_set_policy() path instead of setting it directly.

Re-evaluate policy->boost_supported when highest_perf changes, as
boost capability depends on highest_perf exceeding nominal_perf.

Signed-off-by: Xueqin Luo <luoxueqin@xxxxxxxxxx>
---
 drivers/cpufreq/cppc_cpufreq.c | 39 ++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index bf5175f7551c..56f13086ccee 100644
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -843,6 +843,44 @@ static int cppc_cpufreq_set_boost(struct cpufreq_policy *policy, int state)
 	return 0;
 }
 
+static void cppc_cpufreq_update_limits(struct cpufreq_policy *policy)
+{
+	struct cppc_cpudata *cpu_data = policy->driver_data;
+	u64 prev_highest_perf;
+	u64 highest_perf;
+	int ret;
+
+	guard(cpufreq_policy_write)(policy);
+
+	prev_highest_perf = cpu_data->perf_caps.highest_perf;
+
+	ret = cppc_get_highest_perf(policy->cpu, &highest_perf);
+	if (ret)
+		return;
+
+	if (highest_perf == prev_highest_perf)
+		return;
+
+	cpu_data->perf_caps.highest_perf = highest_perf;
+
+	/*
+	 * Re-evaluate boost capability based on the updated Highest
+	 * Performance. Boost is supported when highest_perf exceeds
+	 * nominal_perf.
+	 */
+	policy->boost_supported = highest_perf >
+				  cpu_data->perf_caps.nominal_perf;
+
+	policy->cpuinfo.max_freq = cppc_perf_to_khz(&cpu_data->perf_caps,
+			policy->boost_enabled ?
+			highest_perf : cpu_data->perf_caps.nominal_perf);
+
+	refresh_frequency_limits(policy);
+
+	pr_debug("CPU%d: highest_perf updated %llu -> %llu\n",
+		 policy->cpu, prev_highest_perf, highest_perf);
+}
+
 static ssize_t show_freqdomain_cpus(struct cpufreq_policy *policy, char *buf)
 {
 	struct cppc_cpudata *cpu_data = policy->driver_data;
@@ -1036,6 +1074,7 @@ static struct cpufreq_driver cppc_cpufreq_driver = {
 	.init = cppc_cpufreq_cpu_init,
 	.exit = cppc_cpufreq_cpu_exit,
 	.set_boost = cppc_cpufreq_set_boost,
+	.update_limits = cppc_cpufreq_update_limits,
 	.attr = cppc_cpufreq_attr,
 	.name = "cppc_cpufreq",
 };
-- 
2.43.0