ARM: OMAP: Simplify dmtimer context-loss handling

The context loss handling in dmtimer appears to assume that
omap_dm_timer_set_load_start() or omap_dm_timer_start() and
omap_dm_timer_stop() bracket all interactions.  Only the first two
restore the context and the last updates the context loss counter.
However omap_dm_timer_set_load() or omap_dm_timer_set_match() can
reasonably be called outside this bracketing, and the fact that they
call omap_dm_timer_enable() / omap_dm_timer_disable() suggest that
is expected.

So if, after a transition into and out of off-mode which would cause
the dm timer to loose all state, omap_dm_timer_set_match() is called
before omap_dm_timer_start(), the value read from OMAP_TIMER_CTRL_REG
will be 'wrong' and this wrong value will be stored context.tclr so
a subsequent omap_dm_timer_start() can fail (As the control register
is wrong).

Simplify this be doing the restore-from-context in
omap_dm_timer_enable() so that whenever the timer is enabled, the
context is correct. Also update the ctx_loss_count at the same time as
we notice it is wrong - these is no value in delaying this until the
omap_dm_timer_disable() as it cannot change while the timer is enabled.
Signed-off-by: NeilBrown <neilb@suse.de>
[jon-hunter@ti.com: minor update to subject and changed variable name]
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Benoit Cousson <benoit.cousson@linaro.org>

arch/arm/plat-omap/dmtimer.c

@@ -315,7 +315,19 @@ EXPORT_SYMBOL_GPL(omap_dm_timer_free);
 
 void omap_dm_timer_enable(struct omap_dm_timer *timer)
 {
+	int c;
+
 	pm_runtime_get_sync(&timer->pdev->dev);
+
+	if (!(timer->capability & OMAP_TIMER_ALWON)) {
+		if (timer->get_context_loss_count) {
+			c = timer->get_context_loss_count(&timer->pdev->dev);
+			if (c != timer->ctx_loss_count) {
+				omap_timer_restore_context(timer);
+				timer->ctx_loss_count = c;
+			}
+		}
+	}
 }
 EXPORT_SYMBOL_GPL(omap_dm_timer_enable);
 
@@ -410,13 +422,6 @@ int omap_dm_timer_start(struct omap_dm_timer *timer)
 
 	omap_dm_timer_enable(timer);
 
-	if (!(timer->capability & OMAP_TIMER_ALWON)) {
-		if (timer->get_context_loss_count &&
-			timer->get_context_loss_count(&timer->pdev->dev) !=
-				timer->ctx_loss_count)
-			omap_timer_restore_context(timer);
-	}
-
 	l = omap_dm_timer_read_reg(timer, OMAP_TIMER_CTRL_REG);
 	if (!(l & OMAP_TIMER_CTRL_ST)) {
 		l |= OMAP_TIMER_CTRL_ST;
@@ -441,12 +446,6 @@ int omap_dm_timer_stop(struct omap_dm_timer *timer)
 
 	__omap_dm_timer_stop(timer, timer->posted, rate);
 
-	if (!(timer->capability & OMAP_TIMER_ALWON)) {
-		if (timer->get_context_loss_count)
-			timer->ctx_loss_count =
-				timer->get_context_loss_count(&timer->pdev->dev);
-	}
-
 	/*
 	 * Since the register values are computed and written within
 	 * __omap_dm_timer_stop, we need to use read to retrieve the
@@ -553,13 +552,6 @@ int omap_dm_timer_set_load_start(struct omap_dm_timer *timer, int autoreload,
 
 	omap_dm_timer_enable(timer);
 
-	if (!(timer->capability & OMAP_TIMER_ALWON)) {
-		if (timer->get_context_loss_count &&
-			timer->get_context_loss_count(&timer->pdev->dev) !=
-				timer->ctx_loss_count)
-			omap_timer_restore_context(timer);
-	}
-
 	l = omap_dm_timer_read_reg(timer, OMAP_TIMER_CTRL_REG);
 	if (autoreload) {
 		l |= OMAP_TIMER_CTRL_AR;