Re: [PATCH 2/4] ACPI: PM: Remove redundant cache flushing

Kirill A. Shutemov
2021-12-09T13:32:16Z

On Tue, Dec 07, 2021 at 05:35:38PM +0100, Rafael J. Wysocki wrote:
> I don't think this is needed for S2, because the function doesn't do
> anything low-level in that case and simply returns (IOW, S2 isn't
> really supported).

Updated patch is below. Does it look good?

From 5eb4ec7d8dd463ba186b779dcef2a802d999c59c Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Date: Thu, 9 Dec 2021 16:08:02 +0300
Subject: [PATCH 1/2] ACPI: PM: Remove redundant cache flushing

ACPICA code takes care about cache flushing on S1/S2/S3 in
acpi_hw_extended_sleep() and acpi_hw_legacy_sleep().

acpi_suspend_enter() calls into ACPICA code via acpi_enter_sleep_state()
for S1 or x86_acpi_suspend_lowlevel() for S3.

acpi_sleep_prepare() call tree:
__acpi_pm_prepare()
acpi_pm_prepare()
acpi_suspend_ops::prepare_late()
acpi_hibernation_ops::pre_snapshot()
acpi_hibernation_ops::prepare()
acpi_suspend_begin_old()
acpi_suspend_begin_old::begin()
acpi_hibernation_begin_old()
acpi_hibernation_ops_old::acpi_hibernation_begin_old()
acpi_power_off_prepare()
pm_power_off_prepare()

Hibernation (S4) and Power Off (S5) don't require cache flushing. So,
the only interesting callsites are acpi_suspend_ops::prepare_late() and
acpi_suspend_begin_old::begin(). Both of them have cache flush on
->enter() operation in acpi_suspend_enter().

Remove redundant ACPI_FLUSH_CPU_CACHE() in acpi_sleep_prepare() and
acpi_suspend_enter().

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
drivers/acpi/sleep.c | 3 ---
1 file changed, 3 deletions(-)

diff --git a/drivers/acpi/sleep.c b/drivers/acpi/sleep.c
index eaa47753b758..5ca6c223ba3d 100644
--- a/drivers/acpi/sleep.c
+++ b/drivers/acpi/sleep.c
@@ -73,7 +73,6 @@ static int acpi_sleep_prepare(u32 acpi_state)
acpi_set_waking_vector(acpi_wakeup_address);

}
- ACPI_FLUSH_CPU_CACHE();
#endif
pr_info("Preparing to enter system sleep state S%d\n", acpi_state);
acpi_enable_wakeup_devices(acpi_state);
@@ -566,8 +565,6 @@ static int acpi_suspend_enter(suspend_state_t pm_state)
u32 acpi_state = acpi_target_sleep_state;
int error;

- ACPI_FLUSH_CPU_CACHE();
-
trace_suspend_resume(TPS("acpi_suspend"), acpi_state, true);
switch (acpi_state) {
case ACPI_STATE_S1:
--
Kirill A. Shutemov