diff mbox

[3.13,03/46] clocksource: vf_pit_timer: use complement for sched_clock reading

Message ID 20140328173135.096192258@linuxfoundation.org (mailing list archive)
State New, archived
Headers show

Commit Message

Greg KH March 28, 2014, 5:31 p.m. UTC 
3.13-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Stefan Agner <stefan@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@agner.ch>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Cc: daniel.lezcano@linaro.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux@arm.linux.org.uk
Link: http://lkml.kernel.org/r/d25af915993aec1b486be653eb86f748ddef54fe.1394057313.git.stefan@agner.ch
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/clocksource/vf_pit_timer.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox

Patch

--- a/drivers/clocksource/vf_pit_timer.c
+++ b/drivers/clocksource/vf_pit_timer.c
@@ -54,7 +54,7 @@  static inline void pit_irq_acknowledge(v
 
 static u64 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)