[PATCH v12 3/9] cpufreq: introduce init_boost callback to initialize boost state for pstate drivers

[Perry Yuan <perry.yuan@amd.com>]

Introduce a new init_boost callback in cpufreq to initialize the boost
state for specific pstate drivers. This initialization is required before
calling the set_boost interface for each CPU.

The init_boost callback will set up and synchronize each CPU's current
boost state before invoking the set_boost function. Without this step,
the boost state may be inconsistent across CPUs.

Signed-off-by: Perry Yuan <perry.yuan@amd.com>
---
 drivers/cpufreq/cpufreq.c | 13 +++++++++++--
 include/linux/cpufreq.h   |  2 ++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 1fdabb660231..64c6770e24c8 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1429,8 +1429,17 @@ static int cpufreq_online(unsigned int cpu)
 			goto out_free_policy;
 		}
 
-		/* Let the per-policy boost flag mirror the cpufreq_driver boost during init */
-		policy->boost_enabled = cpufreq_boost_enabled() && policy_has_boost_freq(policy);
+		/* init boost state to prepare set_boost callback for each CPU */
+		if (cpufreq_driver->init_boost) {
+			ret = cpufreq_driver->init_boost(policy);
+			if (ret)
+				pr_debug("%s: %d: boost initialization failed\n", __func__,
+					__LINE__);
+				goto out_offline_policy;
+		} else {
+			/* Let the per-policy boost flag mirror the cpufreq_driver boost during init */
+			policy->boost_enabled = cpufreq_boost_enabled() && policy_has_boost_freq(policy);
+		}
 
 		/*
 		 * The initialization has succeeded and the policy is online.
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 20f7e98ee8af..0698c0292d8f 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -409,6 +409,8 @@ struct cpufreq_driver {
 	bool		boost_enabled;
 	int		(*set_boost)(struct cpufreq_policy *policy, int state);
 
+	/* initialize boost state to be consistent before calling set_boost */
+	int		(*init_boost)(struct cpufreq_policy *policy);
 	/*
 	 * Set by drivers that want to register with the energy model after the
 	 * policy is properly initialized, but before the governor is started.
-- 
2.34.1