linux-kernel - [PATCH] LoongArch: Implement stable timer shutdown interface

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Date:   Tue, 14 Nov 2023 19:46:56 +0800
From:   Bibo Mao <maobibo@...ngson.cn>
To:     Huacai Chen <chenhuacai@...nel.org>
Cc:     WANG Xuerui <kernel@...0n.name>,
        Peter Zijlstra <peterz@...radead.org>,
        loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: [PATCH] LoongArch: Implement stable timer shutdown interface

When cpu is hotplug out, cpu is in idle state and function
arch_cpu_idle_dead is called. Timer interrupt for this processor should
be disabled, else there will be timer interrupt for the dead cpu. Also
this prevents vcpu to schedule out during halt-polling flow when system
is running in vm mode, since there is pending timer interrupt.

This patch adds detailed implementation for timer shutdown interface, so
that timer will be disabled when cpu is plug-out.

Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
---
 arch/loongarch/kernel/time.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/arch/loongarch/kernel/time.c b/arch/loongarch/kernel/time.c
index 3064af94db9c..2920770e30a9 100644
--- a/arch/loongarch/kernel/time.c
+++ b/arch/loongarch/kernel/time.c
@@ -58,7 +58,7 @@ static int constant_set_state_oneshot(struct clock_event_device *evt)
 	return 0;
 }
 
-static int constant_set_state_oneshot_stopped(struct clock_event_device *evt)
+static int constant_set_state_shutdown(struct clock_event_device *evt)
 {
 	unsigned long timer_config;
 
@@ -90,11 +90,6 @@ static int constant_set_state_periodic(struct clock_event_device *evt)
 	return 0;
 }
 
-static int constant_set_state_shutdown(struct clock_event_device *evt)
-{
-	return 0;
-}
-
 static int constant_timer_next_event(unsigned long delta, struct clock_event_device *evt)
 {
 	unsigned long timer_config;
@@ -161,7 +156,7 @@ int constant_clockevent_init(void)
 	cd->rating = 320;
 	cd->cpumask = cpumask_of(cpu);
 	cd->set_state_oneshot = constant_set_state_oneshot;
-	cd->set_state_oneshot_stopped = constant_set_state_oneshot_stopped;
+	cd->set_state_oneshot_stopped = constant_set_state_shutdown;
 	cd->set_state_periodic = constant_set_state_periodic;
 	cd->set_state_shutdown = constant_set_state_shutdown;
 	cd->set_next_event = constant_timer_next_event;

base-commit: 9bacdd8996c77c42ca004440be610692275ff9d0
-- 
2.39.3