errata: workaround for Neoverse V1 errata 1774420

Neoverse V1 erratum 1774420 is a Cat B erratum present in r0p0 and
r1p0 of the V1 processor core. It is fixed in r1p1.

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

Signed-off-by: Lauren Wehrmeister <lauren.wehrmeister@arm.com>
Change-Id: I66e27b2518f73faeedd8615a1443a74b6a30f123

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

@@ -325,6 +325,10 @@ For Neoverse N1, the following errata build flags are defined :
 
 For Neoverse V1, the following errata build flags are defined :
 
+-  ``ERRATA_V1_1774420``: This applies errata 1774420 workaround to Neoverse-V1
+   CPU. This needs to be enabled only for revisions r0p0 and r1p0, it is fixed
+   in r1p1.
+
 -  ``ERRATA_V1_1791573``: This applies errata 1791573 workaround to Neoverse-V1
    CPU. This needs to be enabled only for revisions r0p0 and r1p0, it is fixed
    in r1p1.

include/lib/cpus/aarch64/neoverse_v1.h

@@ -13,6 +13,7 @@
  * CPU Extended Control register specific definitions.
  ******************************************************************************/
 #define NEOVERSE_V1_CPUECTLR_EL1				S3_0_C15_C1_4
+#define NEOVERSE_V1_CPUECTLR_EL1_BIT_53				(ULL(1) << 53)
 
 /*******************************************************************************
  * CPU Power Control register specific definitions

lib/cpus/aarch64/neoverse_v1.S

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019-2020, ARM Limited. All rights reserved.
+ * Copyright (c) 2019-2021, ARM Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -21,6 +21,34 @@
 #error "Neoverse-V1 supports only AArch64. Compile with CTX_INCLUDE_AARCH32_REGS=0"
 #endif
 
+	/* --------------------------------------------------
+	 * Errata Workaround for Neoverse V1 Errata #1774420.
+	 * This applies to revisions r0p0 and r1p0, fixed in r1p1.
+	 * x0: variant[4:7] and revision[0:3] of current cpu.
+	 * Shall clobber: x0-x17
+	 * --------------------------------------------------
+	 */
+func errata_neoverse_v1_1774420_wa
+	/* Check workaround compatibility. */
+	mov	x17, x30
+	bl	check_errata_1774420
+	cbz	x0, 1f
+
+	/* Set bit 53 in CPUECTLR_EL1 */
+	mrs     x1, NEOVERSE_V1_CPUECTLR_EL1
+	orr	x1, x1, #NEOVERSE_V1_CPUECTLR_EL1_BIT_53
+	msr     NEOVERSE_V1_CPUECTLR_EL1, x1
+	isb
+1:
+	ret	x17
+endfunc errata_neoverse_v1_1774420_wa
+
+func check_errata_1774420
+	/* Applies to r0p0 and r1p0. */
+	mov	x1, #0x10
+	b	cpu_rev_var_ls
+endfunc check_errata_1774420
+
 	/* --------------------------------------------------
 	 * Errata Workaround for Neoverse V1 Errata #1791573.
 	 * This applies to revisions r0p0 and r1p0, fixed in r1p1.
@@ -134,6 +162,7 @@ func neoverse_v1_errata_report
 	 * Report all errata. The revision-variant information is passed to
 	 * checking functions of each errata.
 	 */
+	report_errata ERRATA_V1_1774420, neoverse_v1, 1774420
 	report_errata ERRATA_V1_1791573, neoverse_v1, 1791573
 	report_errata ERRATA_V1_1940577, neoverse_v1, 1940577
 
@@ -149,6 +178,11 @@ func neoverse_v1_reset_func
 	msr	SSBS, xzr
 	isb
 
+#if ERRATA_V1_1774420
+	mov	x0, x18
+	bl	errata_neoverse_v1_1774420_wa
+#endif
+
 #if ERRATA_V1_1791573
 	mov	x0, x18
 	bl	errata_neoverse_v1_1791573_wa

lib/cpus/cpu-ops.mk

@@ -372,6 +372,10 @@ ERRATA_N1_1868343	?=0
 # exists in revisions r0p0, r1p0, and r2p0 as well but there is no workaround.
 ERRATA_N1_1946160	?=0
 
+# Flag to apply erratum 1774420 workaround during reset.  This erratum applies
+# to revisions r0p0 and r1p0 of the Neoverse V1 core, and was fixed in r1p1.
+ERRATA_V1_1774420	?=0
+
 # Flag to apply erratum 1791573 workaround during reset.  This erratum applies
 # to revisions r0p0 and r1p0 of the Neoverse V1 core, and was fixed in r1p1.
 ERRATA_V1_1791573	?=0
@@ -685,6 +689,10 @@ $(eval $(call add_define,ERRATA_N1_1868343))
 $(eval $(call assert_boolean,ERRATA_N1_1946160))
 $(eval $(call add_define,ERRATA_N1_1946160))
 
+# Process ERRATA_V1_1774420 flag
+$(eval $(call assert_boolean,ERRATA_V1_1774420))
+$(eval $(call add_define,ERRATA_V1_1774420))
+
 # Process ERRATA_V1_1791573 flag
 $(eval $(call assert_boolean,ERRATA_V1_1791573))
 $(eval $(call add_define,ERRATA_V1_1791573))