fix(cpus): workaround for Cortex-A710 erratum 2778471

Cortex-A710 erratum 2778471 is a Cat B erratum that applies
to revisions r0p1, r1p0, r2p0 and r2p1 and is still open.
The workaround is to set CPUACTLR3_EL1[47] to 1.

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

Change-Id: Id3bb4a2673e41ff237682e46784d37752daf2f83
Signed-off-by: Sona Mathew <sonarebecca.mathew@arm.com>
diff --git a/lib/cpus/aarch64/cortex_a710.S b/lib/cpus/aarch64/cortex_a710.S
index f3931d7..b99fbb3 100644
--- a/lib/cpus/aarch64/cortex_a710.S
+++ b/lib/cpus/aarch64/cortex_a710.S
@@ -193,6 +193,12 @@
 
 check_erratum_ls cortex_a710, ERRATUM(2768515), CPU_REV(2, 1)
 
+workaround_reset_start cortex_a710, ERRATUM(2778471), ERRATA_A710_2778471
+	sysreg_bit_set CORTEX_A710_CPUACTLR3_EL1, BIT(47)
+workaround_reset_end cortex_a710, ERRATUM(2778471)
+
+check_erratum_ls cortex_a710, ERRATUM(2778471), CPU_REV(2, 1)
+
 workaround_reset_start cortex_a710, CVE(2022, 23960), WORKAROUND_CVE_2022_23960
 #if IMAGE_BL31
 	/*
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index bbf44b4..72a6a20 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -625,6 +625,11 @@
 # still open.
 CPU_FLAG_LIST += ERRATA_A710_2768515
 
+# Flag to apply erratum 2778471 workaround during reset. This erratum applies
+# to revisions r0p0, r1p0, r2p0, r2p1 of the Cortex-A710 cpu and is still
+# open.
+CPU_FLAG_LIST += ERRATA_A710_2778471
+
 # Flag to apply erratum 2002655 workaround during reset. This erratum applies
 # to revisions r0p0 of the Neoverse-N2 cpu and is fixed in r0p1.
 CPU_FLAG_LIST += ERRATA_N2_2002655