[PATCH v3 08/13] ACPI: add perf low power callback

Stephane Eranian
2021-12-01T01:03:08Z

This patch add an optional callback needed by some PMU features, e.g., AMD
BRS, to give a chance to the perf_events code to change its state before
going to low power and after coming back.

The callback is void when the PERF_NEEDS_LOPWR_CB flag is not set.
This flag must be set in arch specific perf_event.h header whenever needed.
When not set, there is no impact of the ACPI code.

Signed-off-by: Stephane Eranian <eranian@google.com>
---
drivers/acpi/acpi_pad.c | 6 ++++++
drivers/acpi/processor_idle.c | 5 +++++
include/linux/perf_event.h | 6 ++++++
3 files changed, 17 insertions(+)

diff --git a/drivers/acpi/acpi_pad.c b/drivers/acpi/acpi_pad.c
index f45979aa2d64..a306a07a60b5 100644
--- a/drivers/acpi/acpi_pad.c
+++ b/drivers/acpi/acpi_pad.c
@@ -164,6 +164,9 @@ static int power_saving_thread(void *data)
tsc_marked_unstable = 1;
}
local_irq_disable();
+
+ perf_lopwr_cb(true);
+
tick_broadcast_enable();
tick_broadcast_enter();
stop_critical_timings();
@@ -172,6 +175,9 @@ static int power_saving_thread(void *data)

start_critical_timings();
tick_broadcast_exit();
+
+ perf_lopwr_cb(false);
+
local_irq_enable();

if (time_before(expire_time, jiffies)) {
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 76ef1bcc8848..7a3a613ae5ed 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -20,6 +20,7 @@
#include <linux/tick.h>
#include <linux/cpuidle.h>
#include <linux/cpu.h>
+#include <linux/perf_event.h>
#include <acpi/processor.h>

/*
@@ -546,6 +547,8 @@ static void wait_for_freeze(void)
*/
static void __cpuidle acpi_idle_do_entry(struct acpi_processor_cx *cx)
{
+ perf_lopwr_cb(true);
+
if (cx->entry_method == ACPI_CSTATE_FFH) {
/* Call into architectural FFH based C-state */
acpi_processor_ffh_cstate_enter(cx);
@@ -556,6 +559,8 @@ static void __cpuidle acpi_idle_do_entry(struct acpi_processor_cx *cx)
inb(cx->address);
wait_for_freeze();
}
+
+ perf_lopwr_cb(false);
}

/**
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index bbe02c80244b..f9760873e145 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1674,4 +1674,10 @@ typedef int (perf_snapshot_branch_stack_t)(struct perf_branch_entry *entries,
unsigned int cnt);
DECLARE_STATIC_CALL(perf_snapshot_branch_stack, perf_snapshot_branch_stack_t);

+#ifndef PERF_NEEDS_LOPWR_CB
+static inline void perf_lopwr_cb(bool mode)
+{
+}
+#endif
+
#endif /* _LINUX_PERF_EVENT_H */
--
2.34.0.rc2.393.gf8c9666880-goog