OMAP2/3: DMTIMER: Clear pending interrupts when stopping a timer

OMAP GP timers keep running for a few cycles after they are stopped,
which can cause the timer to expire and generate an interrupt. The
pending interrupt will prevent e.g. OMAP from entering suspend, thus
we ack it manually.  Only applicable on OMAP2/3/4.

Signed-off-by: Tero Kristo <tero.kristo@nokia.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/plat-omap/dmtimer.c

@@ -551,6 +551,19 @@ void omap_dm_timer_stop(struct omap_dm_timer *timer)
 	if (l & OMAP_TIMER_CTRL_ST) {
 		l &= ~0x1;
 		omap_dm_timer_write_reg(timer, OMAP_TIMER_CTRL_REG, l);
+#if defined(CONFIG_ARCH_OMAP2) || defined(CONFIG_ARCH_OMAP3) || \
+			defined(CONFIG_ARCH_OMAP4)
+		/* Readback to make sure write has completed */
+		omap_dm_timer_read_reg(timer, OMAP_TIMER_CTRL_REG);
+		 /*
+		  * Wait for functional clock period x 3.5 to make sure that
+		  * timer is stopped
+		  */
+		udelay(3500000 / clk_get_rate(timer->fclk) + 1);
+		/* Ack possibly pending interrupt */
+		omap_dm_timer_write_reg(timer, OMAP_TIMER_STAT_REG,
+				OMAP_TIMER_INT_OVERFLOW);
+#endif
 	}
 }
 EXPORT_SYMBOL_GPL(omap_dm_timer_stop);