linux-kernel - [PATCH v1 1/2] cpufreq: intel_pstate: Clear hybrid_max_perf

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Message-ID: <4616631.LvFx2qVVIh@rjwysocki.net>
Date: Mon, 04 Nov 2024 19:51:28 +0100
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
 Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
 Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Subject:
 [PATCH v1 1/2] cpufreq: intel_pstate: Clear hybrid_max_perf_cpu before driver
 registration

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Modify intel_pstate_register_driver() to clear hybrid_max_perf_cpu
before calling cpufreq_register_driver(), so that asymmetric CPU
capacity scaling is not updated until hybrid_init_cpu_capacity_scaling()
runs down the road.  This is done in preparation for a subsequent
change adding asymmetric CPU capacity computation to the CPU init path
to handle CPUs that are initially offline.

The information on whether or not hybrid_max_perf_cpu was NULL before
it has been cleared is passed to hybrid_init_cpu_capacity_scaling(),
so full initialization of CPU capacity scaling can be skipped if it
has been carried out already.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/cpufreq/intel_pstate.c |   21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

Index: linux-pm/drivers/cpufreq/intel_pstate.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/intel_pstate.c
+++ linux-pm/drivers/cpufreq/intel_pstate.c
@@ -1034,7 +1034,7 @@ static void __hybrid_init_cpu_capacity_s
 	hybrid_update_cpu_capacity_scaling();
 }

-static void hybrid_init_cpu_capacity_scaling(void)
+static void hybrid_init_cpu_capacity_scaling(bool refresh)
 {
 	bool disable_itmt = false;

@@ -1045,7 +1045,7 @@ static void hybrid_init_cpu_capacity_sca
 	 * scaling has been enabled already and the driver is just changing the
 	 * operation mode.
 	 */
-	if (hybrid_max_perf_cpu) {
+	if (refresh) {
 		__hybrid_init_cpu_capacity_scaling();
 		goto unlock;
 	}
@@ -1071,6 +1071,18 @@ unlock:
 		sched_clear_itmt_support();
 }

+static bool hybrid_clear_max_perf_cpu(void)
+{
+	bool ret;
+
+	guard(mutex)(&hybrid_capacity_lock);
+
+	ret = !!hybrid_max_perf_cpu;
+	hybrid_max_perf_cpu = NULL;
+
+	return ret;
+}
+
 static void __intel_pstate_get_hwp_cap(struct cpudata *cpu)
 {
 	u64 cap;
@@ -3352,6 +3364,7 @@ static void intel_pstate_driver_cleanup(

 static int intel_pstate_register_driver(struct cpufreq_driver *driver)
 {
+	bool refresh_cpu_cap_scaling;
 	int ret;

 	if (driver == &intel_pstate)
@@ -3364,6 +3377,8 @@ static int intel_pstate_register_driver(

 	arch_set_max_freq_ratio(global.turbo_disabled);

+	refresh_cpu_cap_scaling = hybrid_clear_max_perf_cpu();
+
 	intel_pstate_driver = driver;
 	ret = cpufreq_register_driver(intel_pstate_driver);
 	if (ret) {
@@ -3373,7 +3388,7 @@ static int intel_pstate_register_driver(

 	global.min_perf_pct = min_perf_pct_min();

-	hybrid_init_cpu_capacity_scaling();
+	hybrid_init_cpu_capacity_scaling(refresh_cpu_cap_scaling);

 	return 0;
 }