linux-kernel - [tip:timers/urgent] clocksource: vf_pit_timer: use complement for sched

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Message-ID: <tip-224aa3ed45c8735ae02bb2ecca002409fa6aa772@git.kernel.org>
Date:	Thu, 6 Mar 2014 02:37:20 -0800
From:	tip-bot for Stefan Agner <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	tglx@...utronix.de, shawn.guo@...aro.org, stefan@...er.ch
Subject: [tip:timers/urgent] clocksource: vf_pit_timer:
  use complement for sched_clock reading

Commit-ID:  224aa3ed45c8735ae02bb2ecca002409fa6aa772
Gitweb:     http://git.kernel.org/tip/224aa3ed45c8735ae02bb2ecca002409fa6aa772
Author:     Stefan Agner <stefan@...er.ch>
AuthorDate: Wed, 5 Mar 2014 23:11:08 +0100
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Thu, 6 Mar 2014 11:34:14 +0100

clocksource: vf_pit_timer: use complement for sched_clock reading

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@...er.ch>
Acked-by: Shawn Guo <shawn.guo@...aro.org>
Cc: daniel.lezcano@...aro.org
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux@....linux.org.uk
Link: http://lkml.kernel.org/r/d25af915993aec1b486be653eb86f748ddef54fe.1394057313.git.stefan@agner.ch
Cc: stable@...r.kernel.org
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 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 02821b0..a918bc4 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 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)
--
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