ACPI: processor: idle: Only flush cache on entering C3

kiryl · rafaeljw · commit 87ebbb8c612b · 2021-12-17T18:54:56.000+01:00
According to ACPI 6.4, Section 8.2, CPU cache flushing required on
entering the C3 power state.

Avoid flushing the cache on entering other C-states.

Signed-off-by: Kirill A. Shutemov &lt;kirill.shutemov@linux.intel.com&gt;
[ rjw: Changelog edits ]
Signed-off-by: Rafael J. Wysocki &lt;rafael.j.wysocki@intel.com&gt;
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
@@ -565,7 +565,8 @@ static int acpi_idle_play_dead(struct cpuidle_device *dev, int index)
 {
 	struct acpi_processor_cx *cx = per_cpu(acpi_cstate[index], dev->cpu);
 
-	ACPI_FLUSH_CPU_CACHE();
+	if (cx->type == ACPI_STATE_C3)
+		ACPI_FLUSH_CPU_CACHE();
 
 	while (1) {
 

Original file line number	Diff line number	Diff line change
`@@ -565,7 +565,8 @@ static int acpi_idle_play_dead(struct cpuidle_device *dev, int index)`
`565`	`565`	`{`
`566`	`566`	`struct acpi_processor_cx *cx = per_cpu(acpi_cstate[index], dev->cpu);`
`567`	`567`
`568`		`- ACPI_FLUSH_CPU_CACHE();`
	`568`	`+ if (cx->type == ACPI_STATE_C3)`
	`569`	`+ ACPI_FLUSH_CPU_CACHE();`
`569`	`570`
`570`	`571`	`while (1) {`
`571`	`572`