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arm64: arch_timer: Workaround for Cortex-A73 erratum 858921

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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.

Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
This commit is contained in:
Marc Zyngier 2017-01-27 12:52:31 +00:00
parent a86bd139f2
commit fa8d815fac
2 changed files with 30 additions and 0 deletions
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11
drivers/clocksource/Kconfig
View File

@ -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

19
drivers/clocksource/arm_arch_timer.c
View File

@ -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 = "ARM erratum 858921",
.read_cntvct_el0 = arm64_858921_read_cntvct_el0,
},
#endif
};
typedef bool (*ate_match_fn_t)(const struct arch_timer_erratum_workaround *,