This patch allows a timer-based delay implementation to be selected by
switching the delay routines over to use get_cycles, which is
implemented in terms of read_current_timer. This further allows us to
skip the loop calibration and have a consistent delay function in the
face of core frequency scaling.

To avoid the pain of dealing with memory-mapped counters, this
implementation uses the co-processor interface to the architected timers
when they are available. The previous loop-based implementation is
kept around for CPUs without the architected timers and we retain both
the maximum delay (2ms) and the corresponding conversion factors for
determining the number of loops required for a given interval. Since the
indirection of the timer routines will only work when called from C,
the sa1100 sleep routines are modified to branch to the loop-based delay
functions directly.

Tested-by: Shinya Kuribayashi <shinya.kuribayashi.px@renesas.com>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell 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: Shinya Kuribayashi <shinya.kuribayashi.px@renesas.com>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

When a CPU is shutdown its architected timer comparators registers are
lost. Within CPU idle, before processors enter shutdown they enter
clock events broadcast mode through the

clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, cpuid);

function where the local timers are emulated by a global always-on timer.
On CPU resume, the per-CPU tick device normal mode is restored by exiting
broadcast mode through

clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, cpuid);

In order for this mechanism to function, architected timers should add to
their feature C3STOP, which means that they are not able to function when the
CPU is in off-mode.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Russell 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: Marc Zyngier <marc.zyngier@arm.com>

If CONFIG_LOCAL_TIMERS is not defined, let the architected timer
driver register a single clock_event_device that is used as a
global timer.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Add runtime DT support and documentation for the Cortex A7/A15
architected timers.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Marc 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: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc 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: Marc Zyngier <marc.zyngier@arm.com>