errata: workaround for Neoverse V1 errata 1940577

Neoverse V1 erratum 1940577 is a Cat B erratum, present in some
revisions of the V1 processor core.  The workaround is to insert a
DMB ST before acquire atomic instructions without release semantics.
This issue is present in revisions r0p0 - r1p1  but this workaround
only applies to revisions r1p0 - r1p1, there is no workaround for older
versions.

SDEN can be found here:
https://documentation-service.arm.com/static/60d499080320e92fa40b4625

Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: I210ad7d8f31c81b6ac51b028dfbce75a725c11aa
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index b34fed6..6f80d2d 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -376,6 +376,10 @@
 # to revisions r0p0 and r1p0 of the Neoverse V1 core, and was fixed in r1p1.
 ERRATA_V1_1791573	?=0
 
+# Flag to apply erratum 1940577 workaround during reset. This erratum applies
+# to revisions r1p0 and r1p1 of the Neoverse V1 cpu.
+ERRATA_V1_1940577	?=0
+
 # Flag to apply DSU erratum 798953. This erratum applies to DSUs revision r0p0.
 # Applying the workaround results in higher DSU power consumption on idle.
 ERRATA_DSU_798953	?=0
@@ -685,6 +689,10 @@
 $(eval $(call assert_boolean,ERRATA_V1_1791573))
 $(eval $(call add_define,ERRATA_V1_1791573))
 
+# Process ERRATA_V1_1940577 flag
+$(eval $(call assert_boolean,ERRATA_V1_1940577))
+$(eval $(call add_define,ERRATA_V1_1940577))
+
 # Process ERRATA_DSU_798953 flag
 $(eval $(call assert_boolean,ERRATA_DSU_798953))
 $(eval $(call add_define,ERRATA_DSU_798953))