From: stefan@agner.ch (Stefan Agner)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] clocksource: vf_pit_timer: use complement for sched_clock reading
Date: Wed, 5 Mar 2014 23:11:08 +0100 [thread overview]
Message-ID: <d25af915993aec1b486be653eb86f748ddef54fe.1394057313.git.stefan@agner.ch> (raw)
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>
---
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)
--
1.9.0
next reply other threads:[~2014-03-05 22:11 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-05 22:11 Stefan Agner [this message]
2014-03-06 1:45 ` [PATCH] clocksource: vf_pit_timer: use complement for sched_clock reading Shawn Guo
2014-03-06 3:18 ` Jingchang Lu
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