reboot: Use power off rather than busy spinning when halt is requested

popcornmix · popcornmix · commit 361b309082c7 · 2025-05-23T13:10:42.000+01:00
reboot: Use power off rather than busy spinning when halt is requested

Busy spinning after halt is dumb
We've previously applied this patch to arch/arm
but it is currenltly missing in arch/arm64

Pi4 after "sudo halt" uses 520mA
Pi4 after "sudo shutdown now" uses 310mA

Make them both use the lower powered option

Signed-off-by: Dom Cobley &lt;popcornmix@gmail.com&gt;
diff --git a/arch/arm/kernel/reboot.c b/arch/arm/kernel/reboot.c
@@ -102,9 +102,7 @@ void machine_shutdown(void)
  */
 void machine_halt(void)
 {
-	local_irq_disable();
-	smp_send_stop();
-	while (1);
+	machine_power_off();
 }
 
 /*
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
@@ -98,9 +98,7 @@ void machine_shutdown(void)
  */
 void machine_halt(void)
 {
-	local_irq_disable();
-	smp_send_stop();
-	while (1);
+	machine_power_off();
 }
 
 /*

Original file line number	Diff line number	Diff line change
`@@ -102,9 +102,7 @@ void machine_shutdown(void)`
`102`	`102`	`*/`
`103`	`103`	`void machine_halt(void)`
`104`	`104`	`{`
`105`		`- local_irq_disable();`
`106`		`- smp_send_stop();`
`107`		`- while (1);`
	`105`	`+ machine_power_off();`
`108`	`106`	`}`
`109`	`107`
`110`	`108`	`/*`
Original file line number	Diff line number	Diff line change
`@@ -98,9 +98,7 @@ void machine_shutdown(void)`
`98`	`98`	`*/`
`99`	`99`	`void machine_halt(void)`
`100`	`100`	`{`
`101`		`- local_irq_disable();`
`102`		`- smp_send_stop();`
`103`		`- while (1);`
	`101`	`+ machine_power_off();`
`104`	`102`	`}`
`105`	`103`
`106`	`104`	`/*`