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

Kirill A. Shutemov
2021-12-06T12:30:19Z

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. It only need to flush
cache for S2 (not sure if this call path is ever used for S2).

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 | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/sleep.c b/drivers/acpi/sleep.c
index eaa47753b758..14e8df0ac762 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);
@@ -566,15 +565,15 @@ 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:
barrier();
status = acpi_enter_sleep_state(acpi_state);
break;
-
+ case ACPI_STATE_S2:
+ ACPI_FLUSH_CPU_CACHE();
+ break;
case ACPI_STATE_S3:
if (!acpi_suspend_lowlevel)
return -ENOSYS;
--
2.32.0