fix(cpus): workaround for Cortex-A710 erratum 3701772

Cortex-A710 erratum 3701772 that applies to all revisions <= r2p1
and is still Open.

The workaround is for EL3 software that performs context save/restore
on a change of Security state to use a value of SCR_EL3.NS when
accessing ICH_VMCR_EL2 that reflects the Security state that owns the
data being saved or restored.

SDEN documentation:
https://developer.arm.com/documentation/SDEN-1775101/latest/

Change-Id: I997c9cfaa75321f22b4f690c4d3f234c0b51c670
Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>

docs/design/cpu-specific-build-macros.rst

@@ -653,6 +653,10 @@ For Cortex-A710, the following errata build flags are defined :
    CPU. This needs to be enabled for revisions r0p0, r1p0, r2p0 and r2p1 of the
    CPU and is still open.
 
+- ``ERRATA_A710_3701772``: This applies errata 3701772 workaround to Cortex-A710
+  CPU. This needs to be enabled for revisions r0p0, r1p0, r2p0, r2p1 of the
+  CPU and is still open.
+
 For Neoverse N2, the following errata build flags are defined :
 
 -  ``ERRATA_N2_2002655``: This applies errata 2002655 workaround to Neoverse-N2

include/lib/cpus/aarch64/cortex_a710.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021-2023, Arm Limited. All rights reserved.
+ * Copyright (c) 2021-2025, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -67,4 +67,8 @@
 #define CORTEX_A710_CPUPOR_EL3					S3_6_C15_C8_2
 #define CORTEX_A710_CPUPMR_EL3					S3_6_C15_C8_3
 
+#ifndef __ASSEMBLER__
+long check_erratum_cortex_a710_3701772(long cpu_rev);
+#endif /* __ASSEMBLER__ */
+
 #endif /* CORTEX_A710_H */

lib/cpus/aarch64/cortex_a710.S

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021-2024, Arm Limited. All rights reserved.
+ * Copyright (c) 2021-2025, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -22,6 +22,8 @@
 #error "Cortex A710 supports only AArch64. Compile with CTX_INCLUDE_AARCH32_REGS=0"
 #endif
 
+.global check_erratum_cortex_a710_3701772
+
 #if WORKAROUND_CVE_2022_23960
 	wa_cve_2022_23960_bhb_vector_table CORTEX_A710_BHB_LOOP_COUNT, cortex_a710
 #endif /* WORKAROUND_CVE_2022_23960 */
@@ -218,6 +220,10 @@ workaround_reset_end cortex_a710, CVE(2022, 23960)
 
 check_erratum_chosen cortex_a710, CVE(2022, 23960), WORKAROUND_CVE_2022_23960
 
+add_erratum_entry cortex_a710, ERRATUM(3701772), ERRATA_A710_3701772, NO_APPLY_AT_RESET
+
+check_erratum_ls cortex_a710, ERRATUM(3701772), CPU_REV(2, 1)
+
 	/* ----------------------------------------------------
 	 * HW will do the cache maintenance while powering down
 	 * ----------------------------------------------------

lib/cpus/cpu-ops.mk

@@ -642,6 +642,11 @@ CPU_FLAG_LIST += ERRATA_A710_2768515
 # open.
 CPU_FLAG_LIST += ERRATA_A710_2778471
 
+# Flag to apply erratum  3701772 workaround during context save/restore of
+# ICH_VMCR_EL2 reg. This erratum applies to revisions r0p0, r1p0, r2p0, r2p1
+# of the Cortex-A710 cpu and is still open.
+CPU_FLAG_LIST += ERRATA_A710_3701772
+
 # Flag to apply erratum 2002655 workaround during reset. This erratum applies
 # to revisions r0p0 of the Neoverse-N2 cpu and is fixed in r0p1.
 CPU_FLAG_LIST += ERRATA_N2_2002655

lib/cpus/errata_common.c

@@ -10,6 +10,7 @@
 #include <arch_helpers.h>
 #include <cortex_a75.h>
 #include <cortex_a520.h>
+#include <cortex_a710.h>
 #include <cortex_x4.h>
 #include <lib/cpus/cpu_ops.h>
 #include <lib/cpus/errata.h>
@@ -44,6 +45,13 @@ bool errata_a75_764081_applies(void)
 bool errata_ich_vmcr_el2_applies(void)
 {
 	switch (EXTRACT_PARTNUM(read_midr())) {
+#if ERRATA_A710_3701772
+	case EXTRACT_PARTNUM(CORTEX_A710_MIDR):
+		if (check_erratum_cortex_a710_3701772(cpu_get_rev_var()) == ERRATA_APPLIES)
+			return true;
+		break;
+#endif /* ERRATA_A710_3701772 */
+
 	default:
 		break;
 	}