fix(cpus): workaround for Cortex-A510 erratum 2684597

Cortex-A510 erratum 2684597 is a Cat B erratum that applies to revisions
r0p0, r0p1, r0p2, r0p3, r1p0, r1p1 and r1p2. It is fixed in r1p3. The
workaround is to execute a TSB CSYNC and DSB before executing WFI for
power down.

SDEN can be found here:
https://developer.arm.com/documentation/SDEN1873361/latest
https://developer.arm.com/documentation/SDEN1873351/latest

Change-Id: Ic0b24b600bc013eb59c797401fbdc9bda8058d6d
Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
diff --git a/lib/psci/aarch64/psci_helpers.S b/lib/psci/aarch64/psci_helpers.S
index 0bb1988..61f31e5 100644
--- a/lib/psci/aarch64/psci_helpers.S
+++ b/lib/psci/aarch64/psci_helpers.S
@@ -124,6 +124,9 @@
  * -----------------------------------------------------------------------
  */
 func psci_power_down_wfi
+#if ERRATA_A510_2684597
+	bl apply_cpu_pwr_dwn_errata
+#endif
 	dsb	sy		// ensure write buffer empty
 1:
 	wfi
diff --git a/lib/psci/psci_lib.mk b/lib/psci/psci_lib.mk
index 1d4aac4..6864202 100644
--- a/lib/psci/psci_lib.mk
+++ b/lib/psci/psci_lib.mk
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2016-2017, ARM Limited and Contributors. All rights reserved.
+# Copyright (c) 2016-2023, Arm Limited and Contributors. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -21,7 +21,8 @@
 				lib/psci/${ARCH}/psci_helpers.S
 
 ifeq (${ARCH}, aarch64)
-PSCI_LIB_SOURCES	+=	lib/el3_runtime/aarch64/context.S
+PSCI_LIB_SOURCES	+=	lib/el3_runtime/aarch64/context.S	\
+				lib/cpus/aarch64/runtime_errata.S
 endif
 
 ifeq (${USE_COHERENT_MEM}, 1)
diff --git a/lib/psci/psci_private.h b/lib/psci/psci_private.h
index 1901c17..6ca9ef6 100644
--- a/lib/psci/psci_private.h
+++ b/lib/psci/psci_private.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2022, Arm Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2023, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -304,6 +304,9 @@
  */
 void prepare_cpu_pwr_dwn(unsigned int power_level);
 
+/* This function applies various CPU errata during power down. */
+void apply_cpu_pwr_dwn_errata(void);
+
 /* Private exported functions from psci_on.c */
 int psci_cpu_on_start(u_register_t target_cpu,
 		      const entry_point_info_t *ep);