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Commit d8ec7595 authored by Brian Norris's avatar Brian Norris Committed by Daniel Lezcano
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clocksource/drivers/arm_arch_timer: Don't assume clock runs in suspend 



The ARM specifies that the system counter "must be implemented in an
always-on power domain," and so we try to use the counter as a source of
timekeeping across suspend/resume. Unfortunately, some SoCs (e.g.,
Rockchip's RK3399) do not keep the counter ticking properly when
switched from their high-power clock to the lower-power clock used in
system suspend. Support this quirk by adding a new device tree property.

Signed-off-by: default avatarBrian Norris <briannorris@chromium.org>
Reviewed-by: default avatarDouglas Anderson <dianders@chromium.org>
Acked-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarDaniel Lezcano <daniel.lezcano@linaro.org>
parent baa73d9e

Documentation/devicetree/bindings/arm/arch_timer.txt

+5 −0
Original line number Diff line number Diff line
@@ -38,6 +38,11 @@ to deliver its interrupts via SPIs. 
  architecturally-defined reset values. Only supported for 32-bit

  systems which follow the ARMv7 architected reset values.



- arm,no-tick-in-suspend : The main counter does not tick when the system is in

  low-power system suspend on some SoCs. This behavior does not match the

  Architecture Reference Manual's specification that the system counter "must

  be implemented in an always-on power domain."





Example:

drivers/clocksource/arm_arch_timer.c

+8 −1
Original line number Diff line number Diff line
@@ -81,6 +81,7 @@ static struct clock_event_device __percpu *arch_timer_evt; 
static enum ppi_nr arch_timer_uses_ppi = VIRT_PPI;

static bool arch_timer_c3stop;

static bool arch_timer_mem_use_virtual;

static bool arch_counter_suspend_stop;



static bool evtstrm_enable = IS_ENABLED(CONFIG_ARM_ARCH_TIMER_EVTSTREAM);
@@ -576,7 +577,7 @@ static struct clocksource clocksource_counter = { 
	.rating	= 400,

	.read	= arch_counter_read,

	.mask	= CLOCKSOURCE_MASK(56),

	.flags	= CLOCK_SOURCE_IS_CONTINUOUS | CLOCK_SOURCE_SUSPEND_NONSTOP,

	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,

};



static struct cyclecounter cyclecounter = {
@@ -616,6 +617,8 @@ static void __init arch_counter_register(unsigned type) 
		arch_timer_read_counter = arch_counter_get_cntvct_mem;

	}



	if (!arch_counter_suspend_stop)

		clocksource_counter.flags |= CLOCK_SOURCE_SUSPEND_NONSTOP;

	start_count = arch_timer_read_counter();

	clocksource_register_hz(&clocksource_counter, arch_timer_rate);

	cyclecounter.mult = clocksource_counter.mult;
@@ -907,6 +910,10 @@ static int __init arch_timer_of_init(struct device_node *np) 
	    of_property_read_bool(np, "arm,cpu-registers-not-fw-configured"))

		arch_timer_uses_ppi = PHYS_SECURE_PPI;



	/* On some systems, the counter stops ticking when in suspend. */

	arch_counter_suspend_stop = of_property_read_bool(np,

							 "arm,no-tick-in-suspend");



	return arch_timer_init();

}

CLOCKSOURCE_OF_DECLARE(armv7_arch_timer, "arm,armv7-timer", arch_timer_of_init);