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Commit fa8d815f authored by Marc Zyngier's avatar Marc Zyngier
Browse files

arm64: arch_timer: Workaround for Cortex-A73 erratum 858921 



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: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
parent a86bd139

drivers/clocksource/Kconfig

+11 −0
Original line number Diff line number Diff line
@@ -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

drivers/clocksource/arm_arch_timer.c

+19 −0
Original line number Diff line number Diff line
@@ -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 *,