fix(cpus): workaround for Neoverse N2 erratum 2743089

Neoverse N2 erratum 2743089 is a Cat B erratum that applies to
all revisions <=r0p2 and is fixed in r0p3. The workaround is to
insert a dsb before the isb in the power down sequence.

SDEN documentation:
https://developer.arm.com/documentation/SDEN1982442/latest

Signed-off-by: Bipin Ravi <bipin.ravi@arm.com>
Change-Id: Idec862226bd32c91374a8bbd5d73d7ee480a34d9

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

@@ -574,6 +574,10 @@ For Neoverse N2, the following errata build flags are defined :
    CPU. This needs to be enabled for revision r0p0 of the CPU, it is fixed in
    r0p1.
 
+-  ``ERRATA_N2_2743089``: This applies errata 2743089 workaround to Neoverse-N2
+   CPU. This needs to be enabled for revisions r0p0, r0p1 and r0p2. It is fixed
+   in r0p3.
+
 For Cortex-X2, the following errata build flags are defined :
 
 -  ``ERRATA_X2_2002765``: This applies errata 2002765 workaround to Cortex-X2

lib/cpus/aarch64/neoverse_n2.S

@@ -428,6 +428,30 @@ func check_errata_2388450
 	b	cpu_rev_var_ls
 endfunc check_errata_2388450
 
+/* -------------------------------------------------------
+ * Errata Workaround for Neoverse N2 Erratum 2743089.
+ * This applies to revisions <= r0p2 and is fixed in r0p3.
+ * x0: variant[4:7] and revision[0:3] of current cpu.
+ * Shall clobber: x0-x17
+ * -------------------------------------------------------
+ */
+func errata_n2_2743089_wa
+	mov	x17, x30
+	bl	check_errata_2743089
+	cbz	x0, 1f
+
+	/* dsb before isb of power down sequence */
+	dsb	sy
+1:
+	ret	x17
+endfunc errata_n2_2743089_wa
+
+func check_errata_2743089
+	/* Applies to all revisions <= r0p2 */
+	mov	x1, #0x02
+	b	cpu_rev_var_ls
+endfunc check_errata_2743089
+
 func check_errata_cve_2022_23960
 #if WORKAROUND_CVE_2022_23960
 	mov	x0, #ERRATA_APPLIES
@@ -576,6 +600,12 @@ func neoverse_n2_core_pwr_dwn
 	mrs	x0, NEOVERSE_N2_CPUPWRCTLR_EL1
 	orr	x0, x0, #NEOVERSE_N2_CORE_PWRDN_EN_BIT
 	msr	NEOVERSE_N2_CPUPWRCTLR_EL1, x0
+#if ERRATA_N2_2743089
+	mov	x15, x30
+	bl	cpu_get_rev_var
+	bl	errata_n2_2743089_wa
+	mov	x30, x15
+#endif /* ERRATA_N2_2743089 */
 	isb
 	ret
 endfunc neoverse_n2_core_pwr_dwn
@@ -607,6 +637,7 @@ func neoverse_n2_errata_report
 	report_errata ERRATA_N2_2326639, neoverse_n2, 2326639
 	report_errata ERRATA_N2_2376738, neoverse_n2, 2376738
 	report_errata ERRATA_N2_2388450, neoverse_n2, 2388450
+	report_errata ERRATA_N2_2743089, neoverse_n2, 2743089
 	report_errata WORKAROUND_CVE_2022_23960, neoverse_n2, cve_2022_23960
 	report_errata ERRATA_DSU_2313941, neoverse_n2, dsu_2313941
 

lib/cpus/cpu-ops.mk

@@ -467,10 +467,6 @@ ERRATA_N1_1946160	?=0
 # applies to all revisions <= r4p1 of the Neoverse N1 cpu and is still open.
 ERRATA_N1_2743102	?=0
 
-# Flag to apply erratum 2002655 workaround during reset. This erratum applies
-# to revisions r0p0 of the Neoverse-N2 cpu, it is still open.
-ERRATA_N2_2002655	?=0
-
 # Flag to apply erratum 1618635 workaround during reset. This erratum applies
 # to revision r0p0 of the Neoverse V1 cpu and was fixed in the revision r1p0.
 ERRATA_V1_1618635	?=0
@@ -587,6 +583,10 @@ ERRATA_A710_2371105	?=0
 # still open.
 ERRATA_A710_2768515	?=0
 
+# Flag to apply erratum 2002655 workaround during reset. This erratum applies
+# to revisions r0p0 of the Neoverse-N2 cpu, it is still open.
+ERRATA_N2_2002655	?=0
+
 # Flag to apply erratum 2067956 workaround during reset. This erratum applies
 # to revision r0p0 of the Neoverse N2 cpu and is still open.
 ERRATA_N2_2067956	?=0
@@ -635,6 +635,10 @@ ERRATA_N2_2376738	?=0
 # to revision r0p0 of the Neoverse N2 cpu, it is fixed in r0p1.
 ERRATA_N2_2388450	?=0
 
+# Flag to apply erratum 2743089 workaround during during powerdown. This erratum
+# applies to all revisions <= r0p2 of the Neoverse N2 cpu, it is fixed in r0p3.
+ERRATA_N2_2743089	?=0
+
 # Flag to apply erratum 2002765 workaround during reset. This erratum applies
 # to revisions r0p0, r1p0, and r2p0 of the Cortex-X2 cpu and is still open.
 ERRATA_X2_2002765	?=0
@@ -1123,10 +1127,6 @@ $(eval $(call add_define,ERRATA_N1_1946160))
 # Process ERRATA_N1_2743102 flag
 $(eval $(call assert_boolean,ERRATA_N1_2743102))
 $(eval $(call add_define,ERRATA_N1_2743102))
-#
-# Process ERRATA_N2_2002655 flag
-$(eval $(call assert_boolean,ERRATA_N2_2002655))
-$(eval $(call add_define,ERRATA_N2_2002655))
 
 # Process ERRATA_V1_1618635 flag
 $(eval $(call assert_boolean,ERRATA_V1_1618635))
@@ -1240,6 +1240,10 @@ $(eval $(call add_define,ERRATA_A710_2371105))
 $(eval $(call assert_boolean,ERRATA_A710_2768515))
 $(eval $(call add_define,ERRATA_A710_2768515))
 
+# Process ERRATA_N2_2002655 flag
+$(eval $(call assert_boolean,ERRATA_N2_2002655))
+$(eval $(call add_define,ERRATA_N2_2002655))
+
 # Process ERRATA_N2_2067956 flag
 $(eval $(call assert_boolean,ERRATA_N2_2067956))
 $(eval $(call add_define,ERRATA_N2_2067956))
@@ -1288,6 +1292,10 @@ $(eval $(call add_define,ERRATA_N2_2376738))
 $(eval $(call assert_boolean,ERRATA_N2_2388450))
 $(eval $(call add_define,ERRATA_N2_2388450))
 
+# Process ERRATA_N2_2743089 flag
+$(eval $(call assert_boolean,ERRATA_N2_2743089))
+$(eval $(call add_define,ERRATA_N2_2743089))
+
 # Process ERRATA_X2_2002765 flag
 $(eval $(call assert_boolean,ERRATA_X2_2002765))
 $(eval $(call add_define,ERRATA_X2_2002765))