linux-kernel - [PATCH v2 3/3] intel_idle: Identify the deepest cstate for SRF

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Message-ID: <20241029101507.7188-4-patryk.wlazlyn@linux.intel.com>
Date: Tue, 29 Oct 2024 11:15:07 +0100
From: Patryk Wlazlyn <patryk.wlazlyn@...ux.intel.com>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org,
	rafael.j.wysocki@...el.com,
	len.brown@...el.com,
	artem.bityutskiy@...ux.intel.com,
	dave.hansen@...ux.intel.com,
	patryk.wlazlyn@...ux.intel.com
Subject: [PATCH v2 3/3] intel_idle: Identify the deepest cstate for SRF

On Sierra Forest the mwait hints for subsequent idle states are not
continuous, resulting in play_dead() code not computing the most
optimized idle state when CPU is put offline. This in turn prevents from
entering PC6 state when any of the CPUs in the package is offline.
Force the known, best mwait hint for the deepest cstate.

Signed-off-by: Patryk Wlazlyn <patryk.wlazlyn@...ux.intel.com>
---
 drivers/idle/intel_idle.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 9aab7abc2ae9..d0b4b231d9ad 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -48,6 +48,7 @@
 #include <trace/events/power.h>
 #include <linux/sched.h>
 #include <linux/sched/smt.h>
+#include <linux/smp.h>
 #include <linux/notifier.h>
 #include <linux/cpu.h>
 #include <linux/moduleparam.h>
@@ -1645,6 +1646,7 @@ static bool __init intel_idle_acpi_cst_extract(void)
 static void __init intel_idle_init_cstates_acpi(struct cpuidle_driver *drv)
 {
 	int cstate, limit = min_t(int, CPUIDLE_STATE_MAX, acpi_state_table.count);
+	unsigned int mwait_hint_deepest = 0;
 
 	/*
 	 * If limit > 0, intel_idle_cst_usable() has returned 'true', so all of
@@ -1678,6 +1680,7 @@ static void __init intel_idle_init_cstates_acpi(struct cpuidle_driver *drv)
 			state->target_residency *= 3;
 
 		state->flags = MWAIT2flg(cx->address);
+		mwait_hint_deepest = cx->address;
 		if (cx->type > ACPI_STATE_C2)
 			state->flags |= CPUIDLE_FLAG_TLB_FLUSHED;
 
@@ -1690,6 +1693,9 @@ static void __init intel_idle_init_cstates_acpi(struct cpuidle_driver *drv)
 		state->enter = intel_idle;
 		state->enter_s2idle = intel_idle_s2idle;
 	}
+
+	if (mwait_hint_deepest)
+		smp_set_mwait_play_dead_hint(mwait_hint_deepest);
 }
 
 static bool __init intel_idle_off_by_default(u32 mwait_hint)
@@ -1988,6 +1994,7 @@ static void state_update_enter_method(struct cpuidle_state *state, int cstate)
 
 static void __init intel_idle_init_cstates_icpu(struct cpuidle_driver *drv)
 {
+	unsigned int mwait_hint_deepest = 0;
 	int cstate;
 
 	switch (boot_cpu_data.x86_vfm) {
@@ -2037,6 +2044,8 @@ static void __init intel_idle_init_cstates_icpu(struct cpuidle_driver *drv)
 		if (!intel_idle_verify_cstate(mwait_hint))
 			continue;
 
+		mwait_hint_deepest = mwait_hint;
+
 		/* Structure copy. */
 		drv->states[drv->state_count] = cpuidle_state_table[cstate];
 		state = &drv->states[drv->state_count];
@@ -2060,6 +2069,9 @@ static void __init intel_idle_init_cstates_icpu(struct cpuidle_driver *drv)
 		wrmsrl(MSR_CC6_DEMOTION_POLICY_CONFIG, 0);
 		wrmsrl(MSR_MC6_DEMOTION_POLICY_CONFIG, 0);
 	}
+
+	if (mwait_hint_deepest)
+		smp_set_mwait_play_dead_hint(mwait_hint_deepest);
 }
 
 /**
-- 
2.47.0