clocksource/drivers/timer-rtl-otto: Do not interfere with interrupts

[ Upstream commit c445bff ]

During normal operation the timers are reprogrammed including an
interrupt acknowledgement. This has no effect as the whole timer
is setup from scratch afterwards. Especially in an interrupt this
has already been done by rttm_timer_interrupt().

Change the behaviour as follows:

- Use rttm_disable_timer() during reprogramming
- Keep rttm_stop_timer() for all other use cases.

Downstream has already tested and confirmed a patch. See
openwrt/openwrt#19468
https://forum.openwrt.org/t/support-for-rtl838x-based-managed-switches/57875/3788

Signed-off-by: Markus Stockhausen <[email protected]>
Signed-off-by: Daniel Lezcano <[email protected]>
Tested-by: Stephen Howell <[email protected]>
Tested-by: Bjørn Mork <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sasha Levin <[email protected]>
(cherry picked from commit 8cc561dd9d02f1753ae34dfdd565662828be9a9d)

Author: plappermaul

drivers/clocksource/timer-rtl-otto.c

@@ -147,7 +147,7 @@ static int rttm_next_event(unsigned long delta, struct clock_event_device *clkev
 
 	RTTM_DEBUG(to->of_base.base);
 	rttm_bounce_timer(to->of_base.base, RTTM_CTRL_COUNTER);
-	rttm_stop_timer(to->of_base.base);
+	rttm_disable_timer(to->of_base.base);
 	rttm_set_period(to->of_base.base, delta);
 	rttm_start_timer(to, RTTM_CTRL_COUNTER);
 
@@ -160,7 +160,7 @@ static int rttm_state_oneshot(struct clock_event_device *clkevt)
 
 	RTTM_DEBUG(to->of_base.base);
 	rttm_bounce_timer(to->of_base.base, RTTM_CTRL_COUNTER);
-	rttm_stop_timer(to->of_base.base);
+	rttm_disable_timer(to->of_base.base);
 	rttm_set_period(to->of_base.base, RTTM_TICKS_PER_SEC / HZ);
 	rttm_start_timer(to, RTTM_CTRL_COUNTER);
 
@@ -173,7 +173,7 @@ static int rttm_state_periodic(struct clock_event_device *clkevt)
 
 	RTTM_DEBUG(to->of_base.base);
 	rttm_bounce_timer(to->of_base.base, RTTM_CTRL_TIMER);
-	rttm_stop_timer(to->of_base.base);
+	rttm_disable_timer(to->of_base.base);
 	rttm_set_period(to->of_base.base, RTTM_TICKS_PER_SEC / HZ);
 	rttm_start_timer(to, RTTM_CTRL_TIMER);