fix(cpus): workaround for Neoverse V1 errata 2779461

Neoverse V1 erratum 2779461 is a Cat B erratum that applies to
all revisions <=r1p2 and is still open.

The workaround sets CPUACTLR3_EL1[47] bit to 1. Setting this
bit might have a small impact on power and negligible impact
on performance.

SDEN documentation: https://developer.arm.com/documentation/SDEN1401781/latest

Change-Id: I367cda1779684638063d7292fda20ca6734e6f10
Signed-off-by: Sona Mathew <SonaRebecca.Mathew@arm.com>
(cherry picked from commit 2757da06149238041308060e5cb51f0870a02a15)

4 files changed, 52 insertions, 2 deletions

diff --git a/docs/design/cpu-specific-build-macros.rst b/docs/design/cpu-specific-build-macros.rst
index 4ae4e544c..c4a0e1558 100644
--- a/docs/design/cpu-specific-build-macros.rst
+++ b/docs/design/cpu-specific-build-macros.rst
@@ -472,6 +472,10 @@ For Neoverse V1, the following errata build flags are defined :
    CPU. This needs to be enabled for revisions r0p0, r1p0, r1p1 and r1p2 of the
    CPU. It is still open.
 
+-  ``ERRATA_V1_2779461``: This applies erratum 2779461 workaround to Neoverse-V1
+   CPU. This needs to be enabled for revisions r0p0, r1p0, r1p1, r1p2 of the
+   CPU. It is still open.
+
 For Cortex-A710, the following errata build flags are defined :
 
 -  ``ERRATA_A710_1987031``: This applies errata 1987031 workaround to
diff --git a/include/lib/cpus/aarch64/neoverse_v1.h b/include/lib/cpus/aarch64/neoverse_v1.h
index 9c7e967cb..4c10484f5 100644
--- a/include/lib/cpus/aarch64/neoverse_v1.h
+++ b/include/lib/cpus/aarch64/neoverse_v1.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019-2022, ARM Limited. All rights reserved.
+ * Copyright (c) 2019-2023, ARM Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -41,4 +41,6 @@
 #define NEOVERSE_V1_ACTLR2_EL1_BIT_28				(ULL(1) << 28)
 #define NEOVERSE_V1_ACTLR2_EL1_BIT_40				(ULL(1) << 40)
 
+#define NEOVERSE_V1_ACTLR3_EL1					S3_0_C15_C1_2
+
 #endif /* NEOVERSE_V1_H */
diff --git a/lib/cpus/aarch64/neoverse_v1.S b/lib/cpus/aarch64/neoverse_v1.S
index c3a70ca4c..f9a578985 100644
--- a/lib/cpus/aarch64/neoverse_v1.S
+++ b/lib/cpus/aarch64/neoverse_v1.S
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019-2022, Arm Limited. All rights reserved.
+ * Copyright (c) 2019-2023, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -486,6 +486,35 @@ func check_errata_2743093
 	b	cpu_rev_var_ls
 endfunc check_errata_2743093
 
+	/* ----------------------------------------------------
+ 	 * Errata Workaround for Neoverse V1 Errata #2779461.
+	 * This applies to revisions r0p0, r1p0, r1p1, and r1p2.
+	 * It is still open.
+	 * x0: variant[4:7] and revision[0:3] of current cpu.
+	 * Shall clobber: x0-x1, x17
+	 * ----------------------------------------------------
+	 */
+func errata_neoverse_v1_2779461_wa
+	/* Check revision. */
+	mov	x17, x30
+	bl	check_errata_2779461
+	cbz	x0, 1f
+
+	/* Apply the workaround */
+	mrs	x1, NEOVERSE_V1_ACTLR3_EL1
+	orr	x1, x1, #BIT(47)
+	msr	NEOVERSE_V1_ACTLR3_EL1, x1
+
+1:
+	ret	x17
+endfunc errata_neoverse_v1_2779461_wa
+
+func check_errata_2779461
+	/* Applies to r0p0, r1p0, r1p1, r1p2 */
+	mov	x1, #CPU_REV(1, 2)
+	b	cpu_rev_var_ls
+endfunc check_errata_2779461
+
 func check_errata_cve_2022_23960
 #if WORKAROUND_CVE_2022_23960
 	mov	x0, #ERRATA_APPLIES
@@ -544,6 +573,7 @@ func neoverse_v1_errata_report
 	report_errata ERRATA_V1_2294912, neoverse_v1, 2294912
 	report_errata ERRATA_V1_2372203, neoverse_v1, 2372203
 	report_errata ERRATA_V1_2743093, neoverse_v1, 2743093
+	report_errata ERRATA_V1_2779461, neoverse_v1, 2779461
 	report_errata WORKAROUND_CVE_2022_23960, neoverse_v1, cve_2022_23960
 
 	ldp	x8, x30, [sp], #16
@@ -622,6 +652,11 @@ func neoverse_v1_reset_func
 	bl	errata_neoverse_v1_2372203_wa
 #endif
 
+#if ERRATA_V1_2779461
+	mov	x0, x18
+	bl	errata_neoverse_v1_2779461_wa
+#endif
+
 #if IMAGE_BL31 && WORKAROUND_CVE_2022_23960
 	/*
 	 * The Neoverse-V1 generic vectors are overridden to apply errata
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index ae6baa717..4d50c1bb1 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -526,6 +526,11 @@ ERRATA_V1_2372203	?=0
 # still open.
 ERRATA_V1_2743093	?=0
 
+# Flag to apply erratum 2779461 workaround during powerdown. This erratum
+# applies to revisions r0p0, r1p0, r1p1 and r1p2  of the Neoverse V1 cpu and is
+# still open.
+ERRATA_V1_2779461       ?=0
+
 # Flag to apply erratum 1987031 workaround during reset. This erratum applies
 # to revisions r0p0, r1p0 and r2p0 of the Cortex-A710 cpu and is still open.
 ERRATA_A710_1987031	?=0
@@ -1194,6 +1199,10 @@ $(eval $(call add_define,ERRATA_V1_2372203))
 $(eval $(call assert_boolean,ERRATA_V1_2743093))
 $(eval $(call add_define,ERRATA_V1_2743093))
 
+# Process ERRATA_V1_2779461 flag
+$(eval $(call assert_boolean,ERRATA_V1_2779461))
+$(eval $(call add_define,ERRATA_V1_2779461))
+
 # Process ERRATA_A710_1987031 flag
 $(eval $(call assert_boolean,ERRATA_A710_1987031))
 $(eval $(call add_define,ERRATA_A710_1987031))