clocksource: samsung_pwm_timer: Correct programming of clock events

In current code, the tick count value programmed to the hardware is
always decremented by one. This is reasonable for periodic mode, since
there is one extra tick between 0 and COUNT (after reloading), but it
makes oneshot events happen 1 tick earlier than requested, because the
interrupt is triggered on transition from 1 to 0.

This patch removes the decrementation from PWM channel setup code and
moves it instead to periodic timer setup, to make both periodic and
oneshot modes work correctly.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Olof Johansson <olof@lixom.net>

drivers/clocksource/samsung_pwm_timer.c

@@ -138,8 +138,6 @@ static void samsung_time_setup(unsigned int channel, unsigned long tcnt)
 
 	tcon = __raw_readl(pwm.base + REG_TCON);
 
-	tcnt--;
-
 	tcon &= ~(TCON_START(tcon_chan) | TCON_AUTORELOAD(tcon_chan));
 	tcon |= TCON_MANUALUPDATE(tcon_chan);
 
@@ -187,7 +185,7 @@ static int samsung_set_next_event(unsigned long cycles,
 static void samsung_timer_resume(void)
 {
 	/* event timer restart */
-	samsung_time_setup(pwm.event_id, pwm.clock_count_per_tick);
+	samsung_time_setup(pwm.event_id, pwm.clock_count_per_tick - 1);
 	samsung_time_start(pwm.event_id, true);
 
 	/* source timer restart */
@@ -202,7 +200,7 @@ static void samsung_set_mode(enum clock_event_mode mode,
 
 	switch (mode) {
 	case CLOCK_EVT_MODE_PERIODIC:
-		samsung_time_setup(pwm.event_id, pwm.clock_count_per_tick);
+		samsung_time_setup(pwm.event_id, pwm.clock_count_per_tick - 1);
 		samsung_time_start(pwm.event_id, true);
 		break;