clocksource/drivers/timer-ti-dm: Do reset before enable

Commit 6cfcd556 ("clocksource/drivers/timer-ti-dm: Fix suspend and
resume for am3 and am4") exposed a new issue for type2 dual mode timers
on at least omap5 where the clockevent will stop when the SoC starts
entering idle states during the boot.

Turns out we are wrongly first enabling the system timer and then
resetting it, while we must also re-enable it after reset. The current
sequence leaves the timer module in a partially initialized state. This
issue went unnoticed earlier with ti-sysc driver reconfiguring the timer
module until we fixed the issue of ti-sysc reconfiguring system timers.

Let's fix the issue by calling dmtimer_systimer_enable() from reset for
both type1 and type2 timers, and switch the order of reset and enable in
dmtimer_systimer_setup(). Let's also move dmtimer_systimer_enable() and
dmtimer_systimer_disable() to do this without adding forward declarations.

Fixes: 6cfcd556 ("clocksource/drivers/timer-ti-dm: Fix suspend and resume for am3 and am4")
Reported-by: H. Nikolaus Schaller" <hns@goldelico.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200817092428.6176-1-tony@atomide.com

drivers/clocksource/timer-ti-dm-systimer.c

@@ -69,12 +69,33 @@ static bool dmtimer_systimer_revision1(struct dmtimer_systimer *t)
 	return !(tidr >> 16);
 }
 
+static void dmtimer_systimer_enable(struct dmtimer_systimer *t)
+{
+	u32 val;
+
+	if (dmtimer_systimer_revision1(t))
+		val = DMTIMER_TYPE1_ENABLE;
+	else
+		val = DMTIMER_TYPE2_ENABLE;
+
+	writel_relaxed(val, t->base + t->sysc);
+}
+
+static void dmtimer_systimer_disable(struct dmtimer_systimer *t)
+{
+	if (!dmtimer_systimer_revision1(t))
+		return;
+
+	writel_relaxed(DMTIMER_TYPE1_DISABLE, t->base + t->sysc);
+}
+
 static int __init dmtimer_systimer_type1_reset(struct dmtimer_systimer *t)
 {
 	void __iomem *syss = t->base + OMAP_TIMER_V1_SYS_STAT_OFFSET;
 	int ret;
 	u32 l;
 
+	dmtimer_systimer_enable(t);
 	writel_relaxed(BIT(1) | BIT(2), t->base + t->ifctrl);
 	ret = readl_poll_timeout_atomic(syss, l, l & BIT(0), 100,
 					DMTIMER_RESET_WAIT);
@@ -88,6 +109,7 @@ static int __init dmtimer_systimer_type2_reset(struct dmtimer_systimer *t)
 	void __iomem *sysc = t->base + t->sysc;
 	u32 l;
 
+	dmtimer_systimer_enable(t);
 	l = readl_relaxed(sysc);
 	l |= BIT(0);
 	writel_relaxed(l, sysc);
@@ -336,26 +358,6 @@ static int __init dmtimer_systimer_init_clock(struct dmtimer_systimer *t,
 	return 0;
 }
 
-static void dmtimer_systimer_enable(struct dmtimer_systimer *t)
-{
-	u32 val;
-
-	if (dmtimer_systimer_revision1(t))
-		val = DMTIMER_TYPE1_ENABLE;
-	else
-		val = DMTIMER_TYPE2_ENABLE;
-
-	writel_relaxed(val, t->base + t->sysc);
-}
-
-static void dmtimer_systimer_disable(struct dmtimer_systimer *t)
-{
-	if (!dmtimer_systimer_revision1(t))
-		return;
-
-	writel_relaxed(DMTIMER_TYPE1_DISABLE, t->base + t->sysc);
-}
-
 static int __init dmtimer_systimer_setup(struct device_node *np,
 					 struct dmtimer_systimer *t)
 {
@@ -409,8 +411,8 @@ static int __init dmtimer_systimer_setup(struct device_node *np,
 	t->wakeup = regbase + _OMAP_TIMER_WAKEUP_EN_OFFSET;
 	t->ifctrl = regbase + _OMAP_TIMER_IF_CTRL_OFFSET;
 
-	dmtimer_systimer_enable(t);
 	dmtimer_systimer_reset(t);
+	dmtimer_systimer_enable(t);
 	pr_debug("dmtimer rev %08x sysc %08x\n", readl_relaxed(t->base),
 		 readl_relaxed(t->base + t->sysc));