Re: [PATCH 3/4] ACPI: processor idle: Only flush cache on entering C3
From: Peter Zijlstra <peterz@infradead.org>
Date: 2021-12-06 15:08:41
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On Mon, Dec 06, 2021 at 03:29:51PM +0300, Kirill A. Shutemov wrote:
quoted hunk ↗ jump to hunk
According to the ACPI spec v6.4, section 8.2, cache flushing required on entering C3 power state. Avoid flushing cache on entering other power states. Signed-off-by: Kirill A. Shutemov <redacted> --- drivers/acpi/processor_idle.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index 76ef1bcc8848..01495aca850e 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c@@ -567,7 +567,8 @@ 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();
acpi_idle_enter() already does this, acpi_idle_enter_s2idle() has it confused again, Also, I think acpi_idle_enter() does it too late; consider acpi_idle_enter_mb(). Either that or the BM crud needs more comments.