linux-kernel - Re: [PATCHv2 0/3] clocksource: add db8500 PRCMU timer

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Message-ID: <20110602094622.GS3660@n2100.arm.linux.org.uk>
Date:	Thu, 2 Jun 2011 10:46:22 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Mattias Wallin <mattias.wallin@...ricsson.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Lee Jones <lee.jones@...aro.org>
Subject: Re: [PATCHv2 0/3] clocksource: add db8500 PRCMU timer

On Thu, Jun 02, 2011 at 11:34:31AM +0200, Mattias Wallin wrote:
> The Multi Timer Unit (MTU) is currently used as clocksource and sched_clk
> for the u8500 machine. The MTU block loose power during cpuidle sleep states
> so an alternate clocksource is needed and these patches adds the db8500 PRCMU
> timer.

Why don't we just find a way of fixing sched_clock so that the value
doesn't reset over a suspend/resume cycle?  IOW, lets fix the problem
for _everyone_ rather than only fixing it for one platform at a time.

Could you try this patch to check whether sched_clock() behaves better
across a suspend/resume cycle please?

 arch/arm/kernel/sched_clock.c |   18 ++++++++++++++++++
 1 files changed, 18 insertions(+), 0 deletions(-)

diff --git a/arch/arm/kernel/sched_clock.c b/arch/arm/kernel/sched_clock.c
index 9a46370..4be4019 100644
--- a/arch/arm/kernel/sched_clock.c
+++ b/arch/arm/kernel/sched_clock.c
@@ -10,6 +10,7 @@
 #include <linux/jiffies.h>
 #include <linux/kernel.h>
 #include <linux/sched.h>
+#include <linux/syscore_ops.h>
 #include <linux/timer.h>
 
 #include <asm/sched_clock.h>
@@ -72,3 +73,20 @@ void __init sched_clock_postinit(void)
 {
 	sched_clock_poll(sched_clock_timer.data);
 }
+
+static int sched_clock_suspend(void)
+{
+	sched_clock_poll(sched_clock_timer.data);
+	return 0;
+}
+
+static struct syscore_ops sched_clock_ops = {
+	.suspend	= sched_clock_suspend,
+};
+
+static int __init sched_clock_syscore_init(void)
+{
+	register_syscore_ops(&sched_clock_ops);
+	return 0;
+}
+device_initcall(sched_clock_syscore_init);
--
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