fix(cpus): workaround for Cortex-A78C erratum 2772121

Cortex-A78C erratum 2772121 is a Cat B erratum that applies to
all revisions <=r0p2 and is still open. The workaround is to
insert a dsb before the isb in the power down sequence.

SDEN documentation:
https://developer.arm.com/documentation/SDEN1707916/latest

Signed-off-by: Bipin Ravi <bipin.ravi@arm.com>
Change-Id: I0e190dabffc20c4d3b9b98d1abeb50f308b80bb9

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

@@ -357,6 +357,10 @@ For Cortex-A78C, the following errata build flags are defined :
   Cortex-A78C CPU. This needs to be enabled for revisions r0p1 and r0p2. This
   erratum is still open.
 
+- ``ERRATA_A78C_2772121`` : This applies errata 2772121 workaround to
+  Cortex-A78C CPU. This needs to be enabled for revisions r0p0, r0p1 and r0p2.
+  This erratum is still open.
+
 For Cortex-X1 CPU, the following errata build flags are defined:
 
 - ``ERRATA_X1_1821534`` : This applies errata 1821534 workaround to Cortex-X1

lib/cpus/aarch64/cortex_a78c.S

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021-2022, Arm Limited. All rights reserved.
+ * Copyright (c) 2021-2023, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -117,13 +117,13 @@ func check_errata_2132064
 	b	cpu_rev_var_range
 endfunc check_errata_2132064
 
-/* --------------------------------------------------------------------
+/* ----------------------------------------------------------
  * Errata Workaround for A78C Erratum 2242638.
  * This applies to revisions r0p1 and r0p2 of the Cortex A78C
  * processor and is still open.
  * x0: variant[4:7] and revision[0:3] of current cpu.
  * Shall clobber: x0-x17
- * --------------------------------------------------------------------
+ * ----------------------------------------------------------
  */
 func errata_a78c_2242638_wa
 	/* Compare x0 against revisions r0p1 - r0p2 */
@@ -152,6 +152,31 @@ func check_errata_2242638
 	b	cpu_rev_var_range
 endfunc check_errata_2242638
 
+/* ----------------------------------------------------------------
+ * Errata Workaround for A78C Erratum 2772121.
+ * This applies to revisions r0p0, r0p1 and r0p2 of the Cortex A78C
+ * processor and is still open.
+ * x0: variant[4:7] and revision[0:3] of current cpu.
+ * Shall clobber: x0-x17
+ * ----------------------------------------------------------------
+ */
+func errata_a78c_2772121_wa
+	mov	x17, x30
+	bl	check_errata_2772121
+	cbz	x0, 1f
+
+	/* dsb before isb of power down sequence */
+	dsb	sy
+1:
+	ret	x17
+endfunc errata_a78c_2772121_wa
+
+func check_errata_2772121
+	/* Applies to all revisions <= r0p2 */
+	mov	x1, #0x02
+	b	cpu_rev_var_ls
+endfunc check_errata_2772121
+
 func check_errata_cve_2022_23960
 #if WORKAROUND_CVE_2022_23960
 	mov	x0, #ERRATA_APPLIES
@@ -215,6 +240,12 @@ func cortex_a78c_core_pwr_dwn
 	mrs	x0, CORTEX_A78C_CPUPWRCTLR_EL1
 	orr	x0, x0, #CORTEX_A78C_CPUPWRCTLR_EL1_CORE_PWRDN_EN_BIT
 	msr	CORTEX_A78C_CPUPWRCTLR_EL1, x0
+#if ERRATA_A78C_2772121
+	mov	x15, x30
+	bl	cpu_get_rev_var
+	bl	errata_a78c_2772121_wa
+	mov	x30, x15
+#endif /* ERRATA_A78C_2772121 */
 	isb
 	ret
 endfunc cortex_a78c_core_pwr_dwn
@@ -237,6 +268,7 @@ func cortex_a78c_errata_report
 	report_errata ERRATA_A78C_2242638, cortex_a78c, 2242638
 	report_errata ERRATA_A78C_2376749, cortex_a78c, 2376749
 	report_errata ERRATA_A78C_2395411, cortex_a78c, 2395411
+	report_errata ERRATA_A78C_2772121, cortex_a78c, 2772121
 	report_errata WORKAROUND_CVE_2022_23960, cortex_a78c, cve_2022_23960
 
 	ldp	x8, x30, [sp], #16

lib/cpus/cpu-ops.mk

@@ -394,6 +394,10 @@ ERRATA_A78C_2376749 	?=0
 # to revisions r0p1 and r0p2 of the A78C cpu. It is still open.
 ERRATA_A78C_2395411 	?=0
 
+# Flag to apply erratum 2772121 workaround during powerdown. This erratum
+# applies to revisions r0p0, r0p1 and r0p2 of the A78C cpu. It is still open.
+ERRATA_A78C_2772121 	?=0
+
 # Flag to apply erratum 1821534 workaround during reset. This erratum applies
 # to revisions r0p0 - r1p0 of the X1 cpu and fixed in r1p1.
 ERRATA_X1_1821534	?=0
@@ -1062,6 +1066,10 @@ $(eval $(call add_define,ERRATA_A78C_2376749))
 $(eval $(call assert_boolean,ERRATA_A78C_2395411))
 $(eval $(call add_define,ERRATA_A78C_2395411))
 
+# Process ERRATA_A78C_2772121 flag
+$(eval $(call assert_boolean,ERRATA_A78C_2772121))
+$(eval $(call add_define,ERRATA_A78C_2772121))
+
 # Process ERRATA_X1_1821534 flag
 $(eval $(call assert_boolean,ERRATA_X1_1821534))
 $(eval $(call add_define,ERRATA_X1_1821534))