[PATCH 15/17] arm64: arch_timer: Workaround for Cortex-A73 erratum 858921
Marc Zyngier
marc.zyngier at arm.com
Mon Mar 6 03:26:20 PST 2017
Cortex-A73 (all versions) counter read can return a wrong value
when the counter crosses a 32bit boundary.
The workaround involves performing the read twice, and to return
one or the other depending on whether a transition has taken place.
Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
---
Documentation/arm64/silicon-errata.txt | 1 +
arch/arm64/include/asm/cpucaps.h | 3 ++-
arch/arm64/kernel/cpu_errata.c | 8 ++++++++
drivers/clocksource/Kconfig | 11 +++++++++++
drivers/clocksource/arm_arch_timer.c | 19 +++++++++++++++++++
5 files changed, 41 insertions(+), 1 deletion(-)
diff --git a/Documentation/arm64/silicon-errata.txt b/Documentation/arm64/silicon-errata.txt
index a71b8095dbd8..e0b51bdef445 100644
--- a/Documentation/arm64/silicon-errata.txt
+++ b/Documentation/arm64/silicon-errata.txt
@@ -54,6 +54,7 @@ stable kernels.
| ARM | Cortex-A57 | #852523 | N/A |
| ARM | Cortex-A57 | #834220 | ARM64_ERRATUM_834220 |
| ARM | Cortex-A72 | #853709 | N/A |
+| ARM | Cortex-A73 | #858921 | ARM64_ERRATUM_858921 |
| ARM | MMU-500 | #841119,#826419 | N/A |
| | | | |
| Cavium | ThunderX ITS | #22375, #24313 | CAVIUM_ERRATUM_22375 |
diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index fb78a5d3b60b..b3aab8a17868 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -37,7 +37,8 @@
#define ARM64_HAS_NO_FPSIMD 16
#define ARM64_WORKAROUND_REPEAT_TLBI 17
#define ARM64_WORKAROUND_QCOM_FALKOR_E1003 18
+#define ARM64_WORKAROUND_858921 19
-#define ARM64_NCAPS 19
+#define ARM64_NCAPS 20
#endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 2be1d1c05303..2ed2a7657711 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -158,6 +158,14 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
MIDR_CPU_VAR_REV(0, 0)),
},
#endif
+#ifdef CONFIG_ARM64_ERRATUM_858921
+ {
+ /* Cortex-A73 all versions */
+ .desc = "ARM erratum 858921",
+ .capability = ARM64_WORKAROUND_858921,
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_A73),
+ },
+#endif
{
}
};
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 3356ab821624..af80a7c44faf 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -366,6 +366,17 @@ config HISILICON_ERRATUM_161010101
161010101. The workaround will be active if the hisilicon,erratum-161010101
property is found in the timer node.
+config ARM64_ERRATUM_858921
+ bool "Workaround for Cortex-A73 erratum 858921"
+ default y
+ select ARM_ARCH_TIMER_OOL_WORKAROUND
+ depends on ARM_ARCH_TIMER && ARM64
+ help
+ This option enables a workaround applicable to Cortex-A73
+ (all versions), whose counter may return incorrect values.
+ The workaround will be dynamically enabled when an affected
+ core is detected.
+
config ARM_GLOBAL_TIMER
bool "Support for the ARM global timer" if COMPILE_TEST
select CLKSRC_OF if OF
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 8e3638397347..4eb1109da330 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -266,6 +266,17 @@ static u64 notrace hisi_161010101_read_cntvct_el0(void)
}
#endif
+#ifdef CONFIG_ARM64_ERRATUM_858921
+static u64 notrace arm64_858921_read_cntvct_el0(void)
+{
+ u64 _old, _new;
+
+ _old = read_sysreg(cntvct_el0);
+ _new = read_sysreg(cntvct_el0);
+ return (((_old ^ _new) >> 32) & 1) ? _old : _new;
+}
+#endif
+
#ifdef CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND
DEFINE_PER_CPU(const struct arch_timer_erratum_workaround *,
timer_unstable_counter_workaround);
@@ -331,6 +342,14 @@ static const struct arch_timer_erratum_workaround ool_workarounds[] = {
.set_next_event_virt = erratum_set_next_event_tval_virt,
},
#endif
+#ifdef CONFIG_ARM64_ERRATUM_858921
+ {
+ .match_type = ate_match_local_cap_id,
+ .id = (void *)ARM64_WORKAROUND_858921,
+ .desc_str = "ARM erratum 858921",
+ .read_cntvct_el0 = arm64_858921_read_cntvct_el0,
+ },
+#endif
};
typedef bool (*ate_match_fn_t)(const struct arch_timer_erratum_workaround *,
--
2.11.0
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