arm64: Generic timers support

This patch adds support for the ARM generic timers with A64 instructions
for accessing the timer registers. It uses the physical counter as the
clock source and the virtual counter as sched_clock.

The timer frequency can be specified via DT or read from the CNTFRQ_EL0
register. The physical counter is also accessible from user space
allowing fast gettimeofday() implementation.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index d53cd0afc200..6a78073c3808 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -35,3 +35,8 @@ config CLKSRC_DBX500_PRCMU_SCHED_CLOCK
         default y
         help
           Use the always on PRCMU Timer as sched_clock
+
+config CLKSRC_ARM_GENERIC
+        def_bool y if ARM64
+        help
+          This option enables support for the ARM generic timer.