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: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

1 files changed, 11 insertions, 0 deletions

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