linux-kernel - [PATCH 63/69] clocksource/drivers/arm_global

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Date:	Fri, 18 Dec 2015 15:18:16 +0100
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	tglx@...utronix.de
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	mingo@...nel.org, Grygorii Strashko <grygorii.strashko@...com>,
	Arnd Bergmann <arnd@...db.de>,
	John Stultz <john.stultz@...aro.org>,
	Felipe Balbi <balbi@...com>, Tony Lindgren <tony@...mide.com>,
	Marc Zyngier <marc.zyngier@....com>,
	Srinivas Kandagatla <srinivas.kandagatla@...il.com>,
	Maxime Coquelin <maxime.coquelin@...com>,
	Patrice Chotard <patrice.chotard@...com>,
	kernel@...inux.com (open list:ARM/STI ARCHITECTURE)
Subject: [PATCH 63/69] clocksource/drivers/arm_global_timer: Fix suspend resume

From: Grygorii Strashko <grygorii.strashko@...com>

Now the System stall is observed on TI AM437x based board (am437x-gp-evm)
during resuming from System suspend when ARM Global timer is selected as
clocksource device (CPUIdle not enabled) - SysRq are working, but nothing
else.

The reason of stall is that ARM Global timer loses its contexts during
System suspend:
   GT_CONTROL.TIMER_ENABLE = 0 (unbanked)
   GT_COUNTERx = 0

Hence, update ARM Global timer driver to reflect above behaviour
- re-enable ARM Global timer on resume (GT_CONTROL.TIMER_ENABLE = 1)
  if not enabled.

CC: Arnd Bergmann <arnd@...db.de>
Cc: John Stultz <john.stultz@...aro.org>
Cc: Felipe Balbi <balbi@...com>
Cc: Tony Lindgren <tony@...mide.com>
Cc: Marc Zyngier <marc.zyngier@....com>
Reviewed-by: Santosh Shilimkar <ssantosh@...nel.org>
Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
---
 drivers/clocksource/arm_global_timer.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/clocksource/arm_global_timer.c b/drivers/clocksource/arm_global_timer.c
index f99be6b..d189d8c 100644
--- a/drivers/clocksource/arm_global_timer.c
+++ b/drivers/clocksource/arm_global_timer.c
@@ -195,12 +195,23 @@ static cycle_t gt_clocksource_read(struct clocksource *cs)
 	return gt_counter_read();
 }
 
+static void gt_resume(struct clocksource *cs)
+{
+	unsigned long ctrl;
+
+	ctrl = readl(gt_base + GT_CONTROL);
+	if (!(ctrl & GT_CONTROL_TIMER_ENABLE))
+		/* re-enable timer on resume */
+		writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);
+}
+
 static struct clocksource gt_clocksource = {
 	.name	= "arm_global_timer",
 	.rating	= 300,
 	.read	= gt_clocksource_read,
 	.mask	= CLOCKSOURCE_MASK(64),
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
+	.resume = gt_resume,
 };
 
 #ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
-- 
1.9.1

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