From: Stephane Eranian <eranian@google.com>
Date: Tue, 22 Mar 2022 15:15:12 -0700
Subject: ACPI: Add perf low power callback
Patch-mainline: v5.19-rc1
Git-commit: 2a606a18cd672a16343d146a126721b34cc6adbd
References: jsc#PED-1408, jsc#PED-1755

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
a CPU goes to low power and after it comes 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 on the ACPI code.

Signed-off-by: Stephane Eranian <eranian@google.com>
[peterz: build fix]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220322221517.2510440-9-eranian@google.com
Acked-by: Lee, Chun-Yi <jlee@suse.com>
---
 drivers/acpi/acpi_pad.c       |    7 +++++++
 drivers/acpi/processor_idle.c |    5 +++++
 include/linux/perf_event.h    |    6 ++++++
 3 files changed, 18 insertions(+)

--- a/drivers/acpi/acpi_pad.c
+++ b/drivers/acpi/acpi_pad.c
@@ -17,6 +17,7 @@
 #include <linux/tick.h>
 #include <linux/slab.h>
 #include <linux/acpi.h>
+#include <linux/perf_event.h>
 #include <asm/mwait.h>
 #include <xen/xen.h>
 
@@ -164,6 +165,9 @@ static int power_saving_thread(void *dat
 				tsc_marked_unstable = 1;
 			}
 			local_irq_disable();
+
+			perf_lopwr_cb(true);
+
 			tick_broadcast_enable();
 			tick_broadcast_enter();
 			stop_critical_timings();
@@ -172,6 +176,9 @@ static int power_saving_thread(void *dat
 
 			start_critical_timings();
 			tick_broadcast_exit();
+
+			perf_lopwr_cb(false);
+
 			local_irq_enable();
 
 			if (time_before(expire_time, jiffies)) {
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -21,6 +21,7 @@
 #include <linux/cpuidle.h>
 #include <linux/cpu.h>
 #include <linux/minmax.h>
+#include <linux/perf_event.h>
 #include <acpi/processor.h>
 
 /*
@@ -544,6 +545,8 @@ 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);
@@ -554,6 +557,8 @@ static void __cpuidle acpi_idle_do_entry
 		inb(cx->address);
 		wait_for_freeze();
 	}
+
+	perf_lopwr_cb(false);
 }
 
 /**
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1639,4 +1639,10 @@ typedef int (perf_snapshot_branch_stack_
 					   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 */