Without the isbs in arch_timer_get_cnt{p,v}ct the cpu may speculate
reads and return stale values. This could be bad for code sensitive to
changes in expected deltas between calls (e.g. the delay loop).

Without isbs in arch_timer_reg_write the processor may reorder
instructions around enabling/disabling of the timer or writing the
compare value, which we probably don't want.

This patch adds isbs to prevent those issues.
Signed-off-by: NMark Rutland <mark.rutland@arm.com>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>

Currently the arch_timer register accessors are thrown together with
the main driver, preventing us from porting the driver to other
architectures.

This patch moves the register accessors into a header file, as with
the arm64 version. Constants required by the accessors are also moved.
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>

The current timer-based delay loop relies on the architected timer to
initiate the switch away from the polling-based implementation. This is
unfortunate for platforms without the architected timers but with a
suitable delay source (that is, constant frequency, always powered-up
and ticking as long as the CPUs are online).

This patch introduces a registration mechanism for the delay timer
(which provides an unconditional read_current_timer implementation) and
updates the architected timer code to use the new interface.
Reviewed-by: NStephen Boyd <sboyd@codeaurora.org>
Signed-off-by: NJonathan Austin <jonathan.austin@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Some subsystems (KVM for example) need access to a cycle counter.
In the KVM case, this is used to measure the time delta between
host and guest in order to accurately generate timer events for
the guest.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

This patch implements read_current_timer using the architected timers
when they are selected via CONFIG_ARM_ARCH_TIMER. If they are detected
not to be usable at runtime, we return -ENXIO to the caller.

Furthermore, if read_current_timer is exported then we can implement
get_cycles in terms of it for use as both an entropy source and for
implementing __udelay and friends.
Tested-by: NShinya Kuribayashi <shinya.kuribayashi.px@renesas.com>
Reviewed-by: NStephen Boyd <sboyd@codeaurora.org>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

All mainline platforms using the ARM architected timers are DT
only. As such, remove the ad-hoc support that is not longer needed
anymore.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

Add runtime DT support and documentation for the Cortex A7/A15
architected timers.
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

Provide an A15 sched_clock implementation using the virtual counter,
which is thought to be more useful than the physical one in a
virtualised environment, as it can offset the time spent in another
VM or the hypervisor.
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

Add support for the A15 generic timer and clocksource.
As the timer generates interrupts on a different PPI depending
on the execution mode (normal or secure), it is possible to
register two different PPIs.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>