From 61f0ffc40abf477bbaa2aaa0e3adee504c288c38 Mon Sep 17 00:00:00 2001 From: johpow01 Date: Wed, 5 Aug 2020 12:27:12 -0500 Subject: [PATCH] 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 Change-Id: I37da2b3b2da697701b883bff9a1eff2772352844 --- docs/design/cpu-specific-build-macros.rst | 3 ++ lib/cpus/aarch64/neoverse_n1.S | 38 +++++++++++++++++++++++ lib/cpus/cpu-ops.mk | 8 +++++ 3 files changed, 49 insertions(+) diff --git a/docs/design/cpu-specific-build-macros.rst b/docs/design/cpu-specific-build-macros.rst index 33b509083..3c0e30f79 100644 --- a/docs/design/cpu-specific-build-macros.rst +++ b/docs/design/cpu-specific-build-macros.rst @@ -294,6 +294,9 @@ For Neoverse N1, the following errata build flags are defined : - ``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 5a2b5e452..03ee47209 100644 --- a/lib/cpus/aarch64/neoverse_n1.S +++ b/lib/cpus/aarch64/neoverse_n1.S @@ -388,6 +388,38 @@ func check_errata_1542419 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 @@ func neoverse_n1_reset_func 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 @@ func neoverse_n1_errata_report 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 8fc3b6063..7cd8ed99e 100644 --- a/lib/cpus/cpu-ops.mk +++ b/lib/cpus/cpu-ops.mk @@ -334,6 +334,10 @@ ERRATA_N1_1315703 ?=0 # 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 add_define,ERRATA_N1_1315703)) $(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))