errata: workaround for Neoverse N2 erratum 2025414

Neoverse N2 erratum 2025414 is a Cat B erratum that applies to
revision r0p0 and is still open. The workaround is to set
CPUECLTR_EL1[8] to 1 which disables store issue prefetching.

SDEN can be found here:
https://developer.arm.com/documentation/SDEN1982442/latest

Signed-off-by: Bipin Ravi <bipin.ravi@arm.com>
Change-Id: Ia1c63fb93a1bdb1c3f4cf019a197b2a59233885a

4 files changed, 51 insertions, 6 deletions

diff --git a/docs/design/cpu-specific-build-macros.rst b/docs/design/cpu-specific-build-macros.rst
index 1f998922b..7cda5acd2 100644
--- a/docs/design/cpu-specific-build-macros.rst
+++ b/docs/design/cpu-specific-build-macros.rst
@@ -383,6 +383,9 @@ For Neoverse N2, the following errata build flags are defined :
 -  ``ERRATA_N2_2067956``: This applies errata 2067956 workaround to Neoverse-N2
    CPU. This needs to be enabled for revision r0p0 of the CPU and is still open.
 
+-  ``ERRATA_N2_2025414``: This applies errata 2025414 workaround to Neoverse-N2
+   CPU. This needs to be enabled for revision r0p0 of the CPU and is still open.
+
 DSU Errata Workarounds
 ----------------------
 
diff --git a/include/lib/cpus/aarch64/neoverse_n2.h b/include/lib/cpus/aarch64/neoverse_n2.h
index a7211d218..68f6a40c4 100644
--- a/include/lib/cpus/aarch64/neoverse_n2.h
+++ b/include/lib/cpus/aarch64/neoverse_n2.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, Arm Limited. All rights reserved.
+ * Copyright (c) 2020-2021, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -21,6 +21,7 @@
  ******************************************************************************/
 #define NEOVERSE_N2_CPUECTLR_EL1		S3_0_C15_C1_4
 #define NEOVERSE_N2_CPUECTLR_EL1_EXTLLC_BIT	(ULL(1) << 0)
+#define NEOVERSE_N2_CPUECTLR_EL1_PFSTIDIS_BIT	(ULL(1) << 8)
 
 /*******************************************************************************
  * CPU Auxiliary Control register specific definitions.
diff --git a/lib/cpus/aarch64/neoverse_n2.S b/lib/cpus/aarch64/neoverse_n2.S
index 1ab5412b1..a745ca5d6 100644
--- a/lib/cpus/aarch64/neoverse_n2.S
+++ b/lib/cpus/aarch64/neoverse_n2.S
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, Arm Limited. All rights reserved.
+ * Copyright (c) 2020-2021, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -87,9 +87,36 @@ func check_errata_2067956
 	b	cpu_rev_var_ls
 endfunc check_errata_2067956
 
-	/* -------------------------------------------------
+/* ---------------------------------------------------------------
+ * Errata Workaround for Neoverse N2 Erratum 2025414.
+ * This applies to revision r0p0 of Neoverse N2 and is still open.
+ * Inputs:
+ * x0: variant[4:7] and revision[0:3] of current cpu.
+ * Shall clobber: x0-x17
+ * ---------------------------------------------------------------
+ */
+func errata_n2_2025414_wa
+	/* Compare x0 against revision r0p0 */
+	mov     x17, x30
+	bl      check_errata_2025414
+	cbz     x0, 1f
+	mrs     x1, NEOVERSE_N2_CPUECTLR_EL1
+	orr     x1, x1, NEOVERSE_N2_CPUECTLR_EL1_PFSTIDIS_BIT
+	msr     NEOVERSE_N2_CPUECTLR_EL1, x1
+
+1:
+	ret     x17
+endfunc errata_n2_2025414_wa
+
+func check_errata_2025414
+	/* Applies to r0p0 */
+	mov     x1, #0x00
+	b       cpu_rev_var_ls
+endfunc check_errata_2025414
+
+	/* -------------------------------------------
 	 * The CPU Ops reset function for Neoverse N2.
-	 * -------------------------------------------------
+	 * -------------------------------------------
 	 */
 func neoverse_n2_reset_func
 	mov	x19, x30
@@ -112,6 +139,11 @@ func neoverse_n2_reset_func
 	bl	errata_n2_2067956_wa
 #endif
 
+#if ERRATA_N2_2025414
+	mov     x0, x18
+	bl      errata_n2_2025414_wa
+#endif
+
 #if ENABLE_AMU
 	/* Make sure accesses from EL0/EL1 and EL2 are not trapped to EL3 */
 	mrs	x0, cptr_el3
@@ -146,10 +178,10 @@ func neoverse_n2_reset_func
 endfunc neoverse_n2_reset_func
 
 func neoverse_n2_core_pwr_dwn
-	/* ---------------------------------------------
+	/* ---------------------------------------------------
 	 * Enable CPU power down bit in power control register
 	 * No need to do cache maintenance here.
-	 * ---------------------------------------------
+	 * ---------------------------------------------------
 	 */
 	mrs	x0, NEOVERSE_N2_CPUPWRCTLR_EL1
 	orr	x0, x0, #NEOVERSE_N2_CORE_PWRDN_EN_BIT
@@ -174,6 +206,7 @@ func neoverse_n2_errata_report
 	 */
 	report_errata ERRATA_N2_2002655, neoverse_n2, 2002655
 	report_errata ERRATA_N2_2067956, neoverse_n2, 2067956
+	report_errata ERRATA_N2_2025414, neoverse_n2, 2025414
 
 	ldp	x8, x30, [sp], #16
 	ret
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index b8576e9b5..f93aecdd9 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -425,6 +425,10 @@ ERRATA_A710_2081180	?=0
 # to revision r0p0 of the Neoverse N2 cpu and is still open.
 ERRATA_N2_2067956	?=0
 
+# Flag to apply erratum 2025414 workaround during reset. This erratum applies
+# to revision r0p0 of the Neoverse N2 cpu and is still open.
+ERRATA_N2_2025414	?=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
@@ -782,6 +786,10 @@ $(eval $(call add_define,ERRATA_A710_2081180))
 $(eval $(call assert_boolean,ERRATA_N2_2067956))
 $(eval $(call add_define,ERRATA_N2_2067956))
 
+# Process ERRATA_N2_2025414 flag
+$(eval $(call assert_boolean,ERRATA_N2_2025414))
+$(eval $(call add_define,ERRATA_N2_2025414))
+
 # Process ERRATA_DSU_798953 flag
 $(eval $(call assert_boolean,ERRATA_DSU_798953))
 $(eval $(call add_define,ERRATA_DSU_798953))