[PATCH 3.11 114/144] clocksource: vf_pit_timer: use complement for sched_clock reading

Luis Henriques luis.henriques at canonical.com
Tue Apr 1 04:15:18 PDT 2014 -stable review patch.  If anyone has any objections, please let me know.


From: Stefan Agner <stefan at agner.ch>

commit 224aa3ed45c8735ae02bb2ecca002409fa6aa772 upstream.

Vybrids PIT register is monitonic decreasing. However, sched_clock
reading needs to be monitonic increasing. Use bitwise not to get
the complement of the clock register. This fixes the clock going
backward. Also, the clock now starts at 0 since we load the
register with the maximum value at start.

Signed-off-by: Stefan Agner <stefan at agner.ch>
Acked-by: Shawn Guo <shawn.guo at linaro.org>
Cc: daniel.lezcano at linaro.org
Cc: linux-arm-kernel at lists.infradead.org
Cc: linux at arm.linux.org.uk
Link: http://lkml.kernel.org/r/d25af915993aec1b486be653eb86f748ddef54fe.1394057313.git.stefan@agner.ch
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
 drivers/clocksource/vf_pit_timer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clocksource/vf_pit_timer.c b/drivers/clocksource/vf_pit_timer.c
index 587e020..e559095 100644
--- a/drivers/clocksource/vf_pit_timer.c
+++ b/drivers/clocksource/vf_pit_timer.c
@@ -54,7 +54,7 @@ static inline void pit_irq_acknowledge(void)
 static unsigned int pit_read_sched_clock(void)
-	return __raw_readl(clksrc_base + PITCVAL);
+	return ~__raw_readl(clksrc_base + PITCVAL);
 static int __init pit_clocksource_init(unsigned long rate)

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