Workaround for Neoverse N1 erratum 1800710
Neoverse N1 erratum 1800710 is a Cat B erratum, present in older
revisions of the Neoverse N1 processor core. The workaround is to
set a bit in the ECTLR_EL1 system register, which disables allocation
of splintered pages in the L2 TLB.
This errata is explained in this SDEN:
https://static.docs.arm.com/sden885747/f/Arm_Neoverse_N1_MP050_Software_Developer_Errata_Notice_v21.pdf
Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: Ie5b15c8bc3235e474a06a57c3ec70684361857a6
diff --git a/docs/design/cpu-specific-build-macros.rst b/docs/design/cpu-specific-build-macros.rst
index 6b6c639..78a80f6 100644
--- a/docs/design/cpu-specific-build-macros.rst
+++ b/docs/design/cpu-specific-build-macros.rst
@@ -278,6 +278,9 @@
- ``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_1800710``: This applies errata 1800710 workaround to Neoverse-N1
+ CPU. This needs to be enabled only for revisions <= r4p0 of the CPU.
+
DSU Errata Workarounds
----------------------
diff --git a/include/lib/cpus/aarch64/neoverse_n1.h b/include/lib/cpus/aarch64/neoverse_n1.h
index b50befa..155a90e 100644
--- a/include/lib/cpus/aarch64/neoverse_n1.h
+++ b/include/lib/cpus/aarch64/neoverse_n1.h
@@ -35,6 +35,7 @@
#define NEOVERSE_N1_WS_THR_L2_MASK (ULL(3) << 24)
#define NEOVERSE_N1_CPUECTLR_EL1_MM_TLBPF_DIS_BIT (ULL(1) << 51)
+#define NEOVERSE_N1_CPUECTLR_EL1_BIT_53 (ULL(1) << 53)
#define NEOVERSE_N1_CPUECTLR_EL1_EXTLLC_BIT (ULL(1) << 0)
/*******************************************************************************
diff --git a/lib/cpus/aarch64/neoverse_n1.S b/lib/cpus/aarch64/neoverse_n1.S
index d537ed6..0f80de1 100644
--- a/lib/cpus/aarch64/neoverse_n1.S
+++ b/lib/cpus/aarch64/neoverse_n1.S
@@ -375,6 +375,35 @@
b cpu_rev_var_range
endfunc check_errata_1542419
+/* --------------------------------------------------
+ * Errata Workaround for Neoverse N1 Erratum 1800710.
+ * This applies to revisions <= r4p0 of Neoverse N1
+ * Inputs:
+ * x0: variant[4:7] and revision[0:3] of current cpu.
+ * Shall clobber: x0-x17
+ * --------------------------------------------------
+ */
+func errata_n1_1800710_wa
+ /* Compare x0 against revision <= r4p0 */
+ mov x17, x30
+ bl check_errata_1800710
+ cbz x0, 1f
+
+ /* Disable allocation of splintered pages in the L2 TLB */
+ mrs x1, NEOVERSE_N1_CPUECTLR_EL1
+ orr x1, x1, NEOVERSE_N1_CPUECTLR_EL1_BIT_53
+ msr NEOVERSE_N1_CPUECTLR_EL1, x1
+ isb
+1:
+ ret x17
+endfunc errata_n1_1800710_wa
+
+func check_errata_1800710
+ /* Applies to everything <= r4p0 */
+ mov x1, #0x40
+ b cpu_rev_var_ls
+endfunc check_errata_1800710
+
func neoverse_n1_reset_func
mov x19, x30
@@ -449,6 +478,11 @@
bl errata_n1_1542419_wa
#endif
+#if ERRATA_N1_1800710
+ mov x0, x18
+ bl errata_n1_1800710_wa
+#endif
+
#if ENABLE_AMU
/* Make sure accesses from EL0/EL1 and EL2 are not trapped to EL3 */
mrs x0, actlr_el3
@@ -522,6 +556,7 @@
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_1800710, neoverse_n1, 1800710
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 e494375..3c895f5 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -314,6 +314,10 @@
# to revisions r3p0 - r4p0 of the Neoverse N1 cpu.
ERRATA_N1_1542419 ?=0
+# Flag to apply erratum 1800710 workaround during reset. This erratum applies
+# to revisions <= r4p0 of the Neoverse N1 cpu.
+ERRATA_N1_1800710 ?=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
@@ -563,6 +567,10 @@
$(eval $(call assert_boolean,ERRATA_N1_1542419))
$(eval $(call add_define,ERRATA_N1_1542419))
+# Process ERRATA_N1_1800710 flag
+$(eval $(call assert_boolean,ERRATA_N1_1800710))
+$(eval $(call add_define,ERRATA_N1_1800710))
+
# Process ERRATA_DSU_798953 flag
$(eval $(call assert_boolean,ERRATA_DSU_798953))
$(eval $(call add_define,ERRATA_DSU_798953))