fix(cpus): workaround for Cortex-A710 erratum 2742423

Cortex-A710 erratum 2742423 is a Cat B erratum that applies to all
revisions <= r2p1 and is still open. The workaround is to set
CPUACTLR5_EL1[56:55] to 2'b01.

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

Change-Id: I4d9d3760491f1e6c59b2667c16d59b99cc7979f1
Signed-off-by: Bipin Ravi <bipin.ravi@arm.com>
diff --git a/docs/design/cpu-specific-build-macros.rst b/docs/design/cpu-specific-build-macros.rst
index 9549786..11e7992 100644
--- a/docs/design/cpu-specific-build-macros.rst
+++ b/docs/design/cpu-specific-build-macros.rst
@@ -612,6 +612,10 @@
    interconnect IP. This needs to be enabled for r0p0, r1p0, r2p0 and r2p1 and
    is still open.
 
+-  ``ERRATA_A710_2742423``: This applies errata 2742423 workaround to
+   Cortex-A710 CPU. This needs to be enabled for revisions r0p0, r1p0, r2p0 and
+   r2p1 of the CPU and is still open.
+
 -  ``ERRATA_A710_2768515``: This applies errata 2768515 workaround to
    Cortex-A710 CPU. This needs to be enabled for revisions r0p0, r1p0, r2p0 and
    r2p1 of the CPU and is still open.
diff --git a/lib/cpus/aarch64/cortex_a710.S b/lib/cpus/aarch64/cortex_a710.S
index c618d98..f3931d7 100644
--- a/lib/cpus/aarch64/cortex_a710.S
+++ b/lib/cpus/aarch64/cortex_a710.S
@@ -178,6 +178,14 @@
 
 check_erratum_ls cortex_a710, ERRATUM(2371105), CPU_REV(2, 0)
 
+workaround_reset_start cortex_a710, ERRATUM(2742423), ERRATA_A710_2742423
+	/* Set CPUACTLR5_EL1[56:55] to 2'b01 */
+	sysreg_bit_set CORTEX_A710_CPUACTLR5_EL1, BIT(55)
+	sysreg_bit_clear CORTEX_A710_CPUACTLR5_EL1, BIT(56)
+workaround_reset_end cortex_a710, ERRATUM(2742423)
+
+check_erratum_ls cortex_a710, ERRATUM(2742423), CPU_REV(2, 1)
+
 workaround_runtime_start cortex_a710, ERRATUM(2768515), ERRATA_A710_2768515
 	/* dsb before isb of power down sequence */
 	dsb	sy
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index 39e90ca..8b167a8 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -607,6 +607,11 @@
 # and is still open.
 CPU_FLAG_LIST += ERRATA_A710_2701952
 
+# Flag to apply erratum 2742423 workaround during reset. This erratum applies
+# to revision r0p0, r1p0, r2p0 and r2p1 of the Cortex-A710 cpu and is still
+# open.
+CPU_FLAG_LIST += ERRATA_A710_2742423
+
 # Flag to apply erratum 2768515 workaround during power down. This erratum
 # applies to revision r0p0, r1p0, r2p0 and r2p1 of the Cortex-A710 cpu and is
 # still open.
diff --git a/services/std_svc/errata_abi/errata_abi_main.c b/services/std_svc/errata_abi/errata_abi_main.c
index f2ca0d1..108b8ff 100644
--- a/services/std_svc/errata_abi/errata_abi_main.c
+++ b/services/std_svc/errata_abi/errata_abi_main.c
@@ -328,8 +328,9 @@
 		[13] = {2371105, 0x00, 0x20, ERRATA_A710_2371105},
 		[14] = {2701952, 0x00, 0x21, ERRATA_A710_2701952, \
 			ERRATA_NON_ARM_INTERCONNECT},
-		[15] = {2768515, 0x00, 0x21, ERRATA_A710_2768515},
-		[16 ... ERRATA_LIST_END] = UNDEF_ERRATA,
+		[15] = {2742423, 0x00, 0x21, ERRATA_A710_2742423},
+		[16] = {2768515, 0x00, 0x21, ERRATA_A710_2768515},
+		[17 ... ERRATA_LIST_END] = UNDEF_ERRATA,
 	}
 },
 #endif /* CORTEX_A710_H_INC */