linux-kernel - [PATCH v4] clocksource: arm_global

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Date:	Mon, 30 Nov 2015 20:25:12 +0200
From:	Grygorii Strashko <grygorii.strashko@...com>
To:	Russell King <linux@....linux.org.uk>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Srinivas Kandagatla <srinivas.kandagatla@...il.com>,
	Maxime Coquelin <maxime.coquelin@...com>
CC:	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <kernel@...inux.com>,
	<linux-omap@...r.kernel.org>,
	Santosh Shilimkar <ssantosh@...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>
Subject: [PATCH v4] clocksource: arm_global_timer: fix suspend resume

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>
---
Changes in v4:
 - check current timer's state before enabling.
Changes in v3:
 - dropped all DT specific code
Changes in v2:
 - suspend/resume simplified: nothing is stored any more and
   ARM GT just re-enabled
Links on prev versions:
v3: https://lkml.org/lkml/2015/11/27/402
v2: https://lkml.org/lkml/2015/11/20/355
v1: https://lkml.org/lkml/2015/11/13/456

 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 a2cb6fa..817a787 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
-- 
2.6.3

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