Switching between reading the virtual or physical counters is
problematic, as some core code wants a view of time before we're fully
set up. Using a function pointer and switching the source after the
first read can make time appear to go backwards, and having a check in
the read function is an unfortunate block on what we want to be a fast
path.

Instead, this patch makes us always use the virtual counters. If we're a
guest, or don't have hyp mode, we'll use the virtual timers, and as such
don't care about CNTVOFF as long as it doesn't change in such a way as
to make time appear to travel backwards. As the guest will use the
virtual timers, a (potential) KVM host must use the physical timers
(which can wake up the host even if they fire while a guest is
executing), and hence a host must have CNTVOFF set to zero so as to have
a consistent view of time between the physical timers and virtual
counters.
Signed-off-by: NMark Rutland <mark.rutland@arm.com>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Acked-by: NMarc Zyngier <marc.zyngier@arm.com>
Acked-by: NSantosh Shilimkar <santosh.shilimkar@ti.com>
Cc: Rob Herring <rob.herring@calxeda.com>

This converts arm and arm64 to use CLKSRC_OF DT based initialization for
the arch timer. A new function arch_timer_arch_init is added to allow for
arch specific setup.

This has a side effect of enabling sched_clock on omap5 and exynos5. There
should not be any reason not to use the arch timers for sched_clock.
Signed-off-by: NRob Herring <rob.herring@calxeda.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Kukjin Kim <kgene.kim@samsung.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Simon Horman <horms@verge.net.au>
Cc: Magnus Damm <magnus.damm@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-samsung-soc@vger.kernel.org
Cc: linux-omap@vger.kernel.org
Cc: linux-sh@vger.kernel.org
Acked-by: NSantosh Shilimkar <santosh.shilimkar@ti.com>

Fixes:

In file included from arch/arm/include/asm/arch_timer.h:10:0,
                 from arch/arm/mach-shmobile/timer.c:23:
include/clocksource/arm_arch_timer.h:56:28: warning: 'arch_timer_get_timecounter' defined but not used [-Wunused-function]
Signed-off-by: NOlof Johansson <olof@lixom.net>

The core functionality of the arch_timer driver is not directly tied to
anything under arch/arm, and can be split out.

This patch factors out the core of the arch_timer driver, so it can be
shared with other architectures. A couple of functions are added so
that architecture-specific code can interact with the driver without
needing to touch its internals.

The ARM_ARCH_TIMER config variable is moved out to
drivers/clocksource/Kconfig, existing uses in arch/arm are replaced with
HAVE_ARM_ARCH_TIMER, which selects it.
Signed-off-by: NMark Rutland <mark.rutland@arm.com>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Acked-by: NMarc Zyngier <marc.zyngier@arm.com>