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clocksource/drivers/arm_arch_timer: Work around Hisilicon erratum 161010101

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Erratum Hisilicon-161010101 says that the ARM generic timer counter "has
the potential to contain an erroneous value when the timer value
changes". Accesses to TVAL (both read and write) are also affected due
to the implicit counter read. Accesses to CVAL are not affected.

The workaround is to reread the system count registers until the value
of the second read is larger than the first one by less than 32, the
system counter can be guaranteed not to return wrong value twice by
back-to-back read and the error value is always larger than the correct
one by 32. Writes to TVAL are replaced with an equivalent write to CVAL.

Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
[Mark: split patch, fix Kconfig, reword commit message]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
This commit is contained in:
Ding Tianhong
2017-02-06 16:47:42 +00:00
committed by Daniel Lezcano
parent 16d10ef29f
commit bb42ca4740
2 changed files with 59 additions and 0 deletions
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10
drivers/clocksource/Kconfig
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@@ -356,6 +356,16 @@ config FSL_ERRATUM_A008585
value"). The workaround will only be active if the
fsl,erratum-a008585 property is found in the timer node.
config HISILICON_ERRATUM_161010101
bool "Workaround for Hisilicon Erratum 161010101"
default y
select ARM_ARCH_TIMER_OOL_WORKAROUND
depends on ARM_ARCH_TIMER && ARM64
help
This option enables a workaround for Hisilicon Erratum
161010101. The workaround will be active if the hisilicon,erratum-161010101
property is found in the timer node.
config ARM_GLOBAL_TIMER
bool "Support for the ARM global timer" if COMPILE_TEST
select CLKSRC_OF if OF