linux-kernel - [PATCH] Revert "ACPI: processor: idle: Only flush cache on entering C3"

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Message-Id: <20220403062322.3168-1-akihiko.odaki@gmail.com>
Date:   Sun,  3 Apr 2022 15:23:22 +0900
From:   Akihiko Odaki <akihiko.odaki@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        ak@...ux.intel.com, bp@...en8.de, dan.j.williams@...el.com,
        dave.hansen@...ux.intel.com, hpa@...or.com, knsathya@...nel.org,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        mingo@...hat.com, rjw@...ysocki.net,
        sathyanarayanan.kuppuswamy@...ux.intel.com, tglx@...utronix.de,
        tony.luck@...el.com, x86@...nel.org,
        Akihiko Odaki <akihiko.odaki@...il.com>
Subject: [PATCH] Revert "ACPI: processor: idle: Only flush cache on entering C3"

This reverts commit 87ebbb8c612b1214f227ebb8f25442c6d163e802.

ACPI processor power states can be transitioned in two distinct
situations: 1. when CPU goes idle and 2. before CPU goes offline
("playing dead") to suspend or hibernate. Case 1 is handled by
acpi_idle_enter or acpi_idle_enter_s2idle. Case 2 is handled by
acpi_idle_play_dead.

It is necessary to flush CPU caches in case 2 even if it is not
required to transit ACPI processor power states as CPU will go
offline soon. However, the reverted commit incorrectly removed CPU
cache flushing in such a condition. In fact, it made resuming from
suspend-to-RAM occasionally fail on Lenovo ThinkPad C13 Yoga.

Signed-off-by: Akihiko Odaki <akihiko.odaki@...il.com>
---
 drivers/acpi/processor_idle.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index f8e9fa82cb9b..05b3985a1984 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -570,8 +570,7 @@ static int acpi_idle_play_dead(struct cpuidle_device *dev, int index)
 {
 	struct acpi_processor_cx *cx = per_cpu(acpi_cstate[index], dev->cpu);

-	if (cx->type == ACPI_STATE_C3)
-		ACPI_FLUSH_CPU_CACHE();
+	ACPI_FLUSH_CPU_CACHE();

 	while (1) {

-- 
2.35.1