fix(cpus): workaround for Cortex-A720 erratum 2844092

Cortex-A720 erratum 2844092 is a Cat B erratum that is present
in revisions r0p0, r0p1 and is fixed in r0p2.

The workaround is to set bit[11] of CPUACTLR4_EL1 register.

SDEN documentation:
https://developer.arm.com/documentation/SDEN-2439421/latest

Change-Id: I3d8eacb26cba42774f1f31c3aae2a0e6fecec614
Signed-off-by: Sona Mathew <sonarebecca.mathew@arm.com>

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

@@ -932,6 +932,10 @@ For Cortex-A715, the following errata build flags are defined :
 
 For Cortex-A720, the following errata build flags are defined :
 
+-  ``ERRATA_A720_2844092``: This applies errata 2844092 workaround to
+   Cortex-A720 CPU. This needs to be enabled for revisions r0p0 and r0p1.
+   It is fixed in r0p2.
+
 -  ``ERRATA_A720_2926083``: This applies errata 2926083 workaround to
    Cortex-A720 CPU. This needs to be enabled for revisions r0p0 and r0p1.
    It is fixed in r0p2.

include/lib/cpus/aarch64/cortex_a720.h

@@ -22,6 +22,11 @@
  ******************************************************************************/
 #define CORTEX_A720_CPUACTLR2_EL1				S3_0_C15_C1_1
 
+/*******************************************************************************
+ * CPU Auxiliary Control register 4 specific definitions.
+ ******************************************************************************/
+#define CORTEX_A720_CPUACTLR4_EL1				S3_0_C15_C1_3
+
 /*******************************************************************************
  * CPU Extended Control register specific definitions
  ******************************************************************************/

lib/cpus/aarch64/cortex_a720.S

@@ -26,6 +26,12 @@
         wa_cve_2022_23960_bhb_vector_table CORTEX_A720_BHB_LOOP_COUNT, cortex_a720
 #endif /* WORKAROUND_CVE_2022_23960 */
 
+workaround_reset_start cortex_a720, ERRATUM(2844092), ERRATA_A720_2844092
+        sysreg_bit_set CORTEX_A720_CPUACTLR4_EL1, BIT(11)
+workaround_reset_end cortex_a720, ERRATUM(2844092)
+
+check_erratum_ls cortex_a720, ERRATUM(2844092), CPU_REV(0, 1)
+
 workaround_reset_start cortex_a720, ERRATUM(2926083), ERRATA_A720_2926083
 /* Erratum 2926083 workaround is required only if SPE is enabled */
 #if ENABLE_SPE_FOR_NS != 0

lib/cpus/cpu-ops.mk

@@ -956,6 +956,10 @@ CPU_FLAG_LIST += ERRATA_A715_2561034
 # only to revision r0p0, r1p0 and r1p1. It is fixed in r1p2.
 CPU_FLAG_LIST += ERRATA_A715_2728106
 
+# Flag to apply erratum 2844092 workaround during reset. This erratum applies
+# to revisions r0p0 and r0p1. It is fixed in r0p2.
+CPU_FLAG_LIST += ERRATA_A720_2844092
+
 # Flag to apply erratum 2926083 workaround during reset. This erratum applies
 # to revisions r0p0 and r0p1. It is fixed in r0p2.
 CPU_FLAG_LIST += ERRATA_A720_2926083