Workaround for Neoverse N1 erratum 1868343
Neoverse N1 erratum 1868343 is a Cat B erratum, present in older
revisions of the Neoverse N1 processor core. The workaround is to
set a bit in the CPUACTLR_EL1 system register, which delays instruction
fetch after branch misprediction. This workaround will have a small
impact on performance.
SDEN can be found here:
https://documentation-service.arm.com/static/5f2c130260a93e65927bc92f
Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: I37da2b3b2da697701b883bff9a1eff2772352844
diff --git a/docs/design/cpu-specific-build-macros.rst b/docs/design/cpu-specific-build-macros.rst
index 33b5090..3c0e30f 100644
--- a/docs/design/cpu-specific-build-macros.rst
+++ b/docs/design/cpu-specific-build-macros.rst
@@ -294,6 +294,9 @@
- ``ERRATA_N1_1542419``: This applies errata 1542419 workaround to Neoverse-N1
CPU. This needs to be enabled only for revisions r3p0 - r4p0 of the CPU.
+- ``ERRATA_N1_1868343``: This applies errata 1868343 workaround to Neoverse-N1
+ CPU. This needs to be enabled only for revision <= r4p0 of the CPU.
+
DSU Errata Workarounds
----------------------
diff --git a/lib/cpus/aarch64/neoverse_n1.S b/lib/cpus/aarch64/neoverse_n1.S
index 5a2b5e4..03ee472 100644
--- a/lib/cpus/aarch64/neoverse_n1.S
+++ b/lib/cpus/aarch64/neoverse_n1.S
@@ -388,6 +388,38 @@
b cpu_rev_var_range
endfunc check_errata_1542419
+ /* --------------------------------------------------
+ * Errata Workaround for Neoverse N1 Errata #1868343.
+ * This applies to revision <= r4p0 of Neoverse N1.
+ * This workaround is the same as the workaround for
+ * errata 1262606 and 1275112 but applies to a wider
+ * revision range.
+ * Inputs:
+ * x0: variant[4:7] and revision[0:3] of current cpu.
+ * Shall clobber: x0-x17
+ * --------------------------------------------------
+ */
+func errata_n1_1868343_wa
+ /*
+ * Compare x0 against revision r4p0
+ */
+ mov x17, x30
+ bl check_errata_1868343
+ cbz x0, 1f
+ mrs x1, NEOVERSE_N1_CPUACTLR_EL1
+ orr x1, x1, NEOVERSE_N1_CPUACTLR_EL1_BIT_13
+ msr NEOVERSE_N1_CPUACTLR_EL1, x1
+ isb
+1:
+ ret x17
+endfunc errata_n1_1868343_wa
+
+func check_errata_1868343
+ /* Applies to everything <= r4p0 */
+ mov x1, #0x40
+ b cpu_rev_var_ls
+endfunc check_errata_1868343
+
func neoverse_n1_reset_func
mov x19, x30
@@ -462,6 +494,11 @@
bl errata_n1_1542419_wa
#endif
+#if ERRATA_N1_1868343
+ mov x0, x18
+ bl errata_n1_1868343_wa
+#endif
+
#if ENABLE_AMU
/* Make sure accesses from EL0/EL1 and EL2 are not trapped to EL3 */
mrs x0, actlr_el3
@@ -535,6 +572,7 @@
report_errata ERRATA_N1_1275112, neoverse_n1, 1275112
report_errata ERRATA_N1_1315703, neoverse_n1, 1315703
report_errata ERRATA_N1_1542419, neoverse_n1, 1542419
+ report_errata ERRATA_N1_1868343, neoverse_n1, 1868343
report_errata ERRATA_DSU_936184, neoverse_n1, dsu_936184
ldp x8, x30, [sp], #16
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index 8fc3b60..7cd8ed9 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -334,6 +334,10 @@
# to revisions r3p0 - r4p0 of the Neoverse N1 cpu.
ERRATA_N1_1542419 ?=0
+# Flag to apply erratum 1868343 workaround during reset. This erratum applies
+# to revision <= r4p0 of the Neoverse N1 cpu.
+ERRATA_N1_1868343 ?=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
@@ -603,6 +607,10 @@
$(eval $(call assert_boolean,ERRATA_N1_1542419))
$(eval $(call add_define,ERRATA_N1_1542419))
+# Process ERRATA_N1_1868343 flag
+$(eval $(call assert_boolean,ERRATA_N1_1868343))
+$(eval $(call add_define,ERRATA_N1_1868343))
+
# Process ERRATA_DSU_798953 flag
$(eval $(call assert_boolean,ERRATA_DSU_798953))
$(eval $(call add_define,ERRATA_DSU_798953))