errata: workaround for Neoverse V1 errata 2139242

Neoverse V1 erratum 2139242 is a Cat B erratum present in the V1
processor core.  This issue is present in revisions r0p0, r1p0,
and r1p1, and it is still open.

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

Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: I5c2e9beec72a64ac4131fb6dd76199821a934ebe
diff --git a/docs/design/cpu-specific-build-macros.rst b/docs/design/cpu-specific-build-macros.rst
index 4d7b179..bc277a7 100644
--- a/docs/design/cpu-specific-build-macros.rst
+++ b/docs/design/cpu-specific-build-macros.rst
@@ -349,6 +349,10 @@
    issue is present in r0p0 as well but there is no workaround for that
    revision.  It is still open.
 
+-  ``ERRATA_V1_2139242``: This applies errata 2139242 workaround to Neoverse-V1
+   CPU. This needs to be enabled for revisions r0p0, r1p0, and r1p1 of the
+   CPU.  It is still open.
+
 DSU Errata Workarounds
 ----------------------
 
diff --git a/lib/cpus/aarch64/neoverse_v1.S b/lib/cpus/aarch64/neoverse_v1.S
index f202027..0bcf52a 100644
--- a/lib/cpus/aarch64/neoverse_v1.S
+++ b/lib/cpus/aarch64/neoverse_v1.S
@@ -224,6 +224,41 @@
 	b	cpu_rev_var_range
 endfunc check_errata_1966096
 
+	/* --------------------------------------------------
+	 * Errata Workaround for Neoverse V1 Errata #2139242.
+	 * This applies to revisions r0p0, r1p0, and r1p1, it
+	 * is still open.
+	 * x0: variant[4:7] and revision[0:3] of current cpu.
+	 * Shall clobber: x0-x17
+	 * --------------------------------------------------
+	 */
+func errata_neoverse_v1_2139242_wa
+	/* Check workaround compatibility. */
+	mov	x17, x30
+	bl	check_errata_2139242
+	cbz	x0, 1f
+
+	/* Apply the workaround. */
+	mov	x0, #0x3
+	msr	S3_6_C15_C8_0, x0
+	ldr	x0, =0xEE720F14
+	msr	S3_6_C15_C8_2, x0
+	ldr	x0, =0xFFFF0FDF
+	msr	S3_6_C15_C8_3, x0
+	ldr	x0, =0x40000005003FF
+	msr	S3_6_C15_C8_1, x0
+	isb
+
+1:
+	ret	x17
+endfunc errata_neoverse_v1_2139242_wa
+
+func check_errata_2139242
+	/* Applies to r0p0, r1p0, r1p1 */
+	mov	x1, #0x11
+	b	cpu_rev_var_ls
+endfunc check_errata_2139242
+
 	/* ---------------------------------------------
 	 * HW will do the cache maintenance while powering down
 	 * ---------------------------------------------
@@ -260,6 +295,7 @@
 	report_errata ERRATA_V1_1925756, neoverse_v1, 1925756
 	report_errata ERRATA_V1_1940577, neoverse_v1, 1940577
 	report_errata ERRATA_V1_1966096, neoverse_v1, 1966096
+	report_errata ERRATA_V1_2139242, neoverse_v1, 2139242
 
 	ldp	x8, x30, [sp], #16
 	ret
@@ -303,6 +339,11 @@
 	bl	errata_neoverse_v1_1966096_wa
 #endif
 
+#if ERRATA_V1_2139242
+	mov	x0, x18
+	bl	errata_neoverse_v1_2139242_wa
+#endif
+
 	ret	x19
 endfunc neoverse_v1_reset_func
 
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index 4677f91..050a56e 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -397,6 +397,10 @@
 # exists in r0p0 as well but there is no workaround for that revision.
 ERRATA_V1_1966096   ?=0
 
+# Flag to apply erratum 2139242 workaround during reset. This erratum applies
+# to revisions r0p0, r1p0, and r1p1 of the Neoverse V1 cpu and is still open.
+ERRATA_V1_2139242   ?=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
@@ -726,6 +730,10 @@
 $(eval $(call assert_boolean,ERRATA_V1_1966096))
 $(eval $(call add_define,ERRATA_V1_1966096))
 
+# Process ERRATA_V1_2139242 flag
+$(eval $(call assert_boolean,ERRATA_V1_2139242))
+$(eval $(call add_define,ERRATA_V1_2139242))
+
 # Process ERRATA_DSU_798953 flag
 $(eval $(call assert_boolean,ERRATA_DSU_798953))
 $(eval $(call add_define,ERRATA_DSU_798953))