linux-kernel - [PATCH v1 2/5] cpufreq: intel_pstate: Simplify spinlock locking

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Date: Thu, 21 Mar 2024 20:30:42 +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>
Subject: [PATCH v1 2/5] cpufreq: intel_pstate: Simplify spinlock locking

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

Because intel_pstate_enable/disable_hwp_interrupt() are only called from
thread context, they need not save the IRQ flags when using a spinlock
as interrupts are guaranteed to be enabled when they run, so make them
use spin_lock/unlock_irq().

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/cpufreq/intel_pstate.c |   12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

Index: linux-pm/drivers/cpufreq/intel_pstate.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/intel_pstate.c
+++ linux-pm/drivers/cpufreq/intel_pstate.c
@@ -1682,30 +1682,26 @@ ack_intr:
 
 static void intel_pstate_disable_hwp_interrupt(struct cpudata *cpudata)
 {
-	unsigned long flags;
-
 	if (!boot_cpu_has(X86_FEATURE_HWP_NOTIFY))
 		return;
 
 	/* wrmsrl_on_cpu has to be outside spinlock as this can result in IPC */
 	wrmsrl_on_cpu(cpudata->cpu, MSR_HWP_INTERRUPT, 0x00);
 
-	spin_lock_irqsave(&hwp_notify_lock, flags);
+	spin_lock_irq(&hwp_notify_lock);
 	if (cpumask_test_and_clear_cpu(cpudata->cpu, &hwp_intr_enable_mask))
 		cancel_delayed_work(&cpudata->hwp_notify_work);
-	spin_unlock_irqrestore(&hwp_notify_lock, flags);
+	spin_unlock_irq(&hwp_notify_lock);
 }
 
 static void intel_pstate_enable_hwp_interrupt(struct cpudata *cpudata)
 {
 	/* Enable HWP notification interrupt for guaranteed performance change */
 	if (boot_cpu_has(X86_FEATURE_HWP_NOTIFY)) {
-		unsigned long flags;
-
-		spin_lock_irqsave(&hwp_notify_lock, flags);
+		spin_lock_irq(&hwp_notify_lock);
 		INIT_DELAYED_WORK(&cpudata->hwp_notify_work, intel_pstate_notify_work);
 		cpumask_set_cpu(cpudata->cpu, &hwp_intr_enable_mask);
-		spin_unlock_irqrestore(&hwp_notify_lock, flags);
+		spin_unlock_irq(&hwp_notify_lock);
 
 		/* wrmsrl_on_cpu has to be outside spinlock as this can result in IPC */
 		wrmsrl_on_cpu(cpudata->cpu, MSR_HWP_INTERRUPT, 0x01);