feat(cpus): workaround for Cortex A78 AE erratum 1951502

Cortex A78 AE erratum 1951502 is a Cat B erratum that applies to revisions
<= r0p1. It is still open. This erratum is avoided by inserting a DMB ST
before acquire atomic instructions without release semantics through a series
of writes to implementation defined system registers.

SDEN is available at https://developer.arm.com/documentation/SDEN1707912/0900

Change-Id: I812c5a37cdd03486df8af6046d9fa988f6a0a098
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>

2 files changed, 88 insertions, 11 deletions

diff --git a/lib/cpus/aarch64/cortex_a78_ae.S b/lib/cpus/aarch64/cortex_a78_ae.S
index 9aff9ac85..c8cccf278 100644
--- a/lib/cpus/aarch64/cortex_a78_ae.S
+++ b/lib/cpus/aarch64/cortex_a78_ae.S
@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2019-2020, ARM Limited. All rights reserved.
+ * Copyright (c) 2021, NVIDIA Corporation. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -16,12 +17,73 @@
 #error "cortex_a78_ae must be compiled with HW_ASSISTED_COHERENCY enabled"
 #endif
 
+/* --------------------------------------------------
+ * Errata Workaround for A78 AE Erratum 1951502.
+ * This applies to revisions r0p0 and r0p1 of A78 AE.
+ * Inputs:
+ * x0: variant[4:7] and revision[0:3] of current cpu.
+ * Shall clobber: x0-x17
+ * --------------------------------------------------
+ */
+func errata_a78_ae_1951502_wa
+	/* Compare x0 against revisions r0p0 - r0p1 */
+	mov	x17, x30
+	bl	check_errata_1951502
+	cbz	x0, 1f
+
+	msr	S3_6_c15_c8_0, xzr
+	ldr	x0, =0x10E3900002
+	msr	S3_6_c15_c8_2, x0
+	ldr	x0, =0x10FFF00083
+	msr	S3_6_c15_c8_3, x0
+	ldr	x0, =0x2001003FF
+	msr	S3_6_c15_c8_1, x0
+
+	mov	x0, #1
+	msr	S3_6_c15_c8_0, x0
+	ldr	x0, =0x10E3800082
+	msr	S3_6_c15_c8_2, x0
+	ldr	x0, =0x10FFF00083
+	msr	S3_6_c15_c8_3, x0
+	ldr	x0, =0x2001003FF
+	msr	S3_6_c15_c8_1, x0
+
+	mov	x0, #2
+	msr	S3_6_c15_c8_0, x0
+	ldr	x0, =0x10E3800200
+	msr	S3_6_c15_c8_2, x0
+	ldr	x0, =0x10FFF003E0
+	msr	S3_6_c15_c8_3, x0
+	ldr	x0, =0x2001003FF
+	msr	S3_6_c15_c8_1, x0
+
+	isb
+1:
+	ret	x17
+endfunc errata_a78_ae_1951502_wa
+
+func check_errata_1951502
+	/* Applies to revisions r0p0 and r0p1. */
+	mov	x1, #CPU_REV(0, 0)
+	mov	x2, #CPU_REV(0, 1)
+	b	cpu_rev_var_range
+endfunc check_errata_1951502
+
 	/* -------------------------------------------------
 	 * The CPU Ops reset function for Cortex-A78-AE
 	 * -------------------------------------------------
 	 */
-#if ENABLE_AMU
 func cortex_a78_ae_reset_func
+	mov	x19, x30
+	bl	cpu_get_rev_var
+	mov	x18, x0
+
+#if ERRATA_A78_AE_1951502
+	mov	x0, x18
+	bl	errata_a78_ae_1951502_wa
+#endif
+
+#if ENABLE_AMU
 	/* Make sure accesses from EL0/EL1 and EL2 are not trapped to EL3 */
 	mrs	x0, actlr_el3
 	bic	x0, x0, #CORTEX_A78_ACTLR_TAM_BIT
@@ -39,11 +101,12 @@ func cortex_a78_ae_reset_func
 	/* Enable group1 counters */
 	mov	x0, #CORTEX_A78_AMU_GROUP1_MASK
 	msr	CPUAMCNTENSET1_EL0, x0
+#endif
+
 	isb
 
-	ret
+	ret	x19
 endfunc cortex_a78_ae_reset_func
-#endif
 
 	/* -------------------------------------------------------
 	 * HW will do the cache maintenance while powering down
@@ -66,6 +129,18 @@ endfunc cortex_a78_ae_core_pwr_dwn
 	 */
 #if REPORT_ERRATA
 func cortex_a78_ae_errata_report
+	stp	x8, x30, [sp, #-16]!
+
+	bl	cpu_get_rev_var
+	mov	x8, x0
+
+	/*
+	 * Report all errata. The revision-variant information is passed to
+	 * checking functions of each errata.
+	 */
+	report_errata ERRATA_A78_AE_1951502, cortex_a78_ae, 1951502
+
+	ldp	x8, x30, [sp], #16
 	ret
 endfunc cortex_a78_ae_errata_report
 #endif
@@ -89,12 +164,6 @@ func cortex_a78_ae_cpu_reg_dump
 	ret
 endfunc cortex_a78_ae_cpu_reg_dump
 
-#if ENABLE_AMU
-#define A78_AE_RESET_FUNC cortex_a78_ae_reset_func
-#else
-#define A78_AE_RESET_FUNC CPU_NO_RESET_FUNC
-#endif
-
 declare_cpu_ops cortex_a78_ae, CORTEX_A78_AE_MIDR, \
-	A78_AE_RESET_FUNC, \
+	cortex_a78_ae_reset_func, \
 	cortex_a78_ae_core_pwr_dwn
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index 050a56e4f..b36616760 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -1,6 +1,6 @@
 #
 # Copyright (c) 2014-2021, ARM Limited and Contributors. All rights reserved.
-# Copyright (c) 2020, NVIDIA Corporation. All rights reserved.
+# Copyright (c) 2020-2021, NVIDIA Corporation. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -311,6 +311,10 @@ ERRATA_A78_1941498	?=0
 # well but there is no workaround for that revision.
 ERRATA_A78_1951500	?=0
 
+# Flag to apply erratum 1951502 workaround during reset. This erratum applies
+# to revisions r0p0 and r0p1 of the A78 AE cpu. It is still open.
+ERRATA_A78_AE_1951502	?=0
+
 # Flag to apply erratum 1821534 workaround during reset. This erratum applies
 # to revisions r0p0 and r1p0 of the A78 cpu.
 ERRATA_A78_1821534	?=0
@@ -646,6 +650,10 @@ $(eval $(call add_define,ERRATA_A78_1941498))
 $(eval $(call assert_boolean,ERRATA_A78_1951500))
 $(eval $(call add_define,ERRATA_A78_1951500))
 
+# Process ERRATA_A78_AE_1951502 flag
+$(eval $(call assert_boolean,ERRATA_A78_AE_1951502))
+$(eval $(call add_define,ERRATA_A78_AE_1951502))
+
 # Process ERRATA_A78_1821534 flag
 $(eval $(call assert_boolean,ERRATA_A78_1821534))
 $(eval $(call add_define,ERRATA_A78_1821534))