fix(cpus): workaround for Cortex-A78 erratum 2779479

Cortex-A78 erratum 2779479 is a Cat B erratum that applies to
all revisions <= r1p2 and is still open.

The workaround is to set the 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/SDEN1401784/latest

Change-Id: I3779fd1eff3017c5961ffa101b357918070b3b36
Signed-off-by: Sona Mathew <SonaRebecca.Mathew@arm.com>

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

@@ -321,6 +321,10 @@ For Cortex-A78, the following errata build flags are defined :
    CPU. This needs to be enabled for revisions r0p0, r1p0, r1p1, and r1p2, and
    it is still open.
 
+-  ``ERRATA_A78_2779479``: This applies erratum 2779479 workaround to Cortex-A78
+   CPU. This needs to be enabled for revisions r0p0, r1p0, r1p1 and r1p2 and
+   it is still open.
+
 For Cortex-A78 AE, the following errata build flags are defined :
 
 - ``ERRATA_A78_AE_1941500`` : This applies errata 1941500 workaround to

include/lib/cpus/aarch64/cortex_a78.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
  */
@@ -40,6 +40,8 @@
 #define CORTEX_A78_ACTLR2_EL1_BIT_2			(ULL(1) << 2)
 #define CORTEX_A78_ACTLR2_EL1_BIT_40			(ULL(1) << 40)
 
+#define CORTEX_A78_ACTLR3_EL1				S3_0_C15_C1_2
+
 /*******************************************************************************
  * CPU Activity Monitor Unit register specific definitions.
  ******************************************************************************/

lib/cpus/aarch64/cortex_a78.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
  */
@@ -351,6 +351,35 @@ func check_errata_2772019
 	b	cpu_rev_var_ls
 endfunc check_errata_2772019
 
+/* ----------------------------------------------------
+ * Errata Workaround for Cortex A78 Errata 2779479.
+ * 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_a78_2779479_wa
+	/* Check revision. */
+	mov	x17, x30
+	bl	check_errata_2779479
+	cbz	x0, 1f
+
+	/* Apply the workaround */
+	mrs	x1, CORTEX_A78_ACTLR3_EL1
+	orr	x1, x1, #BIT(47)
+	msr	CORTEX_A78_ACTLR3_EL1, x1
+
+1:
+	ret	x17
+endfunc errata_a78_2779479_wa
+
+func check_errata_2779479
+	/* Applies to r0p0, r1p0, r1p1, r1p2 */
+	mov	x1, #CPU_REV(1, 2)
+	b	cpu_rev_var_ls
+endfunc check_errata_2779479
+
 func check_errata_cve_2022_23960
 #if WORKAROUND_CVE_2022_23960
 	mov	x0, #ERRATA_APPLIES
@@ -414,6 +443,11 @@ func cortex_a78_reset_func
 	bl	errata_a78_2395406_wa
 #endif
 
+#if ERRATA_A78_2779479
+	mov	x0, x18
+	bl	errata_a78_2779479_wa
+#endif
+
 #if ENABLE_AMU
 	/* Make sure accesses from EL0/EL1 and EL2 are not trapped to EL3 */
 	mrs	x0, actlr_el3
@@ -493,6 +527,7 @@ func cortex_a78_errata_report
 	report_errata ERRATA_A78_2376745, cortex_a78, 2376745
 	report_errata ERRATA_A78_2395406, cortex_a78, 2395406
 	report_errata ERRATA_A78_2772019, cortex_a78, 2772019
+	report_errata ERRATA_A78_2779479, cortex_a78, 2779479
 	report_errata WORKAROUND_CVE_2022_23960, cortex_a78, cve_2022_23960
 
 	ldp	x8, x30, [sp], #16

lib/cpus/cpu-ops.mk

@@ -362,6 +362,10 @@ ERRATA_A78_2395406	?=0
 # open.
 ERRATA_A78_2772019	?=0
 
+# Flag to apply erratum 2779479 workaround during reset. This erratum applies
+# to revision r0p0, r1p0, r1p1 and r1p2 of the A78 cpu. It is still open.
+ERRATA_A78_2779479	?=0
+
 # Flag to apply erratum 1941500 workaround during reset. This erratum applies
 # to revisions r0p0 and r0p1 of the A78 AE cpu. It is still open.
 ERRATA_A78_AE_1941500	?=0
@@ -1030,6 +1034,10 @@ $(eval $(call add_define,ERRATA_A78_2395406))
 $(eval $(call assert_boolean,ERRATA_A78_2772019))
 $(eval $(call add_define,ERRATA_A78_2772019))
 
+# Process ERRATA_A78_2779479 flag
+$(eval $(call assert_boolean,ERRATA_A78_2779479))
+$(eval $(call add_define,ERRATA_A78_2779479))
+
 # Process ERRATA_A78_AE_1941500 flag
 $(eval $(call assert_boolean,ERRATA_A78_AE_1941500))
 $(eval $(call add_define,ERRATA_A78_AE_1941500))