fix(cpus): workaround for Cortex-X4 erratum 2763018

Cortex-X4 erratum 2763018 is a Cat B erratum that is present
in revisions r0p0, r0p1 and is fixed in r0p2.

The workaround is to set bit[47] of CPUACTLR3_EL1 register.
Setting this chicken bit might have a small impact on power
and negligible impact on performance.

SDEN documentation:
https://developer.arm.com/documentation/SDEN2432808/latest

Change-Id: Ia188e08c2eb2952923ec72e2a56efdeea836fe1e
Signed-off-by: Sona Mathew <sonarebecca.mathew@arm.com>

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

@@ -830,6 +830,9 @@ For Cortex-X4, the following errata build flags are defined :
    CPU. This needs to be enabled for revisions r0p0 and r0p1. It is fixed
    in r0p2.
 
+- ``ERRATA_X4_2763018``: This applies errata 2763018 workaround to Cortex-X4
+  CPU. This needs to be enabled for revisions r0p0 and r0p1. It is fixed in r0p2.
+
 For Cortex-A510, the following errata build flags are defined :
 
 -  ``ERRATA_A510_1922240``: This applies errata 1922240 workaround to

include/lib/cpus/aarch64/cortex_x4.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022-2023, Arm Limited. All rights reserved.
+ * Copyright (c) 2022-2024, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -23,4 +23,9 @@
 #define CORTEX_X4_CPUPWRCTLR_EL1			S3_0_C15_C2_7
 #define CORTEX_X4_CPUPWRCTLR_EL1_CORE_PWRDN_BIT		U(1)
 
+/*******************************************************************************
+ * CPU Auxiliary control register specific definitions
+ ******************************************************************************/
+#define CORTEX_X4_CPUACTLR3_EL1				S3_0_C15_C1_2
+
 #endif /* CORTEX_X4_H */

lib/cpus/aarch64/cortex_x4.S

@@ -33,6 +33,12 @@ workaround_runtime_end cortex_x4, ERRATUM(2740089)
 
 check_erratum_ls cortex_x4, ERRATUM(2740089), CPU_REV(0, 1)
 
+workaround_reset_start cortex_x4, ERRATUM(2763018), ERRATA_X4_2763018
+	sysreg_bit_set	CORTEX_X4_CPUACTLR3_EL1, BIT(47)
+workaround_reset_end cortex_x4, ERRATUM(2763018)
+
+check_erratum_ls cortex_x4, ERRATUM(2763018), CPU_REV(0, 1)
+
 workaround_reset_start cortex_x4, CVE(2022, 23960), WORKAROUND_CVE_2022_23960
 #if IMAGE_BL31
 	/*

lib/cpus/cpu-ops.mk

@@ -827,6 +827,10 @@ CPU_FLAG_LIST += ERRATA_X4_2701112
 # applies to all revisions <= r0p1 of the Cortex-X4 cpu, it is fixed in r0p2.
 CPU_FLAG_LIST += ERRATA_X4_2740089
 
+# Flag to apply erratum 2763018 workaround on reset. This erratum applies
+# to revisions r0p0 and r0p1 of the Cortex-X4 cpu. It is fixed in r0p2.
+CPU_FLAG_LIST += ERRATA_X4_2763018
+
 # Flag to apply erratum 1922240 workaround during reset. This erratum applies
 # to revision r0p0 of the Cortex-A510 cpu and is fixed in r0p1.
 CPU_FLAG_LIST += ERRATA_A510_1922240