power: ab8500_chargalg: Use CLOCK_MONOTONIC

The HRTimer in the AB8500 charging code is using CLOCK_REALTIME
to set an alarm some hours forward in time +/- 5 min for a safety
timer.

I have observed that this will sometimes fire sporadically
early when charging a battery with the result that
charging stops.

As CLOCK_REALTIME can be subject to adjustments of time from
sources such as NTP, this cannot be trusted and will likely
for example fire events if the clock is set forward some hours
by say NTP.

Use CLOCK_MONOTONIC as indicated in other instances and the
problem goes away. Also initialize the timer to REL mode
as this is what will be used later.

Fixes: 257107ae ("ab8500-chargalg: Use hrtimer")
Cc: Lee Jones <lee.jones@linaro.org>
Suggested-by: Matti Vaittinen <mazziesaccount@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/ab8500_chargalg.c

@@ -1775,11 +1775,11 @@ static int ab8500_chargalg_probe(struct platform_device *pdev)
 	psy_cfg.drv_data = di;
 
 	/* Initilialize safety timer */
-	hrtimer_init(&di->safety_timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
+	hrtimer_init(&di->safety_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	di->safety_timer.function = ab8500_chargalg_safety_timer_expired;
 
 	/* Initilialize maintenance timer */
-	hrtimer_init(&di->maintenance_timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
+	hrtimer_init(&di->maintenance_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	di->maintenance_timer.function =
 		ab8500_chargalg_maintenance_timer_expired;