linux-kernel - [PATCH 04/21] ARM: OMAP: 32k counter: Provide y2038-safe omap_read_persistent

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Date:	Wed,  1 Apr 2015 20:34:24 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	lkml <linux-kernel@...r.kernel.org>
Cc:	Xunlei Pang <pang.xunlei@...aro.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	John Stultz <john.stultz@...aro.org>
Subject: [PATCH 04/21] ARM: OMAP: 32k counter: Provide y2038-safe omap_read_persistent_clock() replacement

From: Xunlei Pang <pang.xunlei@...aro.org>

As part of addressing "y2038 problem" for in-kernel uses, this
patch adds the y2038-safe omap_read_persistent_clock64() using
timespec64.

Because we rely on some subsequent changes to convert arm multiarch
support, omap_read_persistent_clock() will be removed then.

Also remove the needless spinlock, because read_persistent_clock()
doesn't run simultaneously.

Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Acked-by: Tony Lindgren <tony@...mide.com>
Signed-off-by: Xunlei Pang <pang.xunlei@...aro.org>
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
 arch/arm/plat-omap/counter_32k.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/arch/arm/plat-omap/counter_32k.c b/arch/arm/plat-omap/counter_32k.c
index 43cf745..b7b7b07 100644
--- a/arch/arm/plat-omap/counter_32k.c
+++ b/arch/arm/plat-omap/counter_32k.c
@@ -44,24 +44,20 @@ static u64 notrace omap_32k_read_sched_clock(void)
 }
 
 /**
- * omap_read_persistent_clock -  Return time from a persistent clock.
+ * omap_read_persistent_clock64 -  Return time from a persistent clock.
  *
  * Reads the time from a source which isn't disabled during PM, the
  * 32k sync timer.  Convert the cycles elapsed since last read into
- * nsecs and adds to a monotonically increasing timespec.
+ * nsecs and adds to a monotonically increasing timespec64.
  */
-static struct timespec persistent_ts;
+static struct timespec64 persistent_ts;
 static cycles_t cycles;
 static unsigned int persistent_mult, persistent_shift;
-static DEFINE_SPINLOCK(read_persistent_clock_lock);
 
-static void omap_read_persistent_clock(struct timespec *ts)
+static void omap_read_persistent_clock64(struct timespec64 *ts)
 {
 	unsigned long long nsecs;
 	cycles_t last_cycles;
-	unsigned long flags;
-
-	spin_lock_irqsave(&read_persistent_clock_lock, flags);
 
 	last_cycles = cycles;
 	cycles = sync32k_cnt_reg ? readl_relaxed(sync32k_cnt_reg) : 0;
@@ -69,11 +65,17 @@ static void omap_read_persistent_clock(struct timespec *ts)
 	nsecs = clocksource_cyc2ns(cycles - last_cycles,
 					persistent_mult, persistent_shift);
 
-	timespec_add_ns(&persistent_ts, nsecs);
+	timespec64_add_ns(&persistent_ts, nsecs);
 
 	*ts = persistent_ts;
+}
+
+static void omap_read_persistent_clock(struct timespec *ts)
+{
+	struct timespec64 ts64;
 
-	spin_unlock_irqrestore(&read_persistent_clock_lock, flags);
+	omap_read_persistent_clock64(&ts64);
+	*ts = timespec64_to_timespec(ts64);
 }
 
 /**
-- 
1.9.1

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