[PATCH 62/69] clocksource/drivers/pistachio: Fix wrong calculated clocksource read value

Daniel Lezcano
2015-12-18T14:23:54Z

From: Jisheng Zhang <jszhang@marvell.com>

Let's assume the counter value is 0xf0000000, the pistachio clocksource
read cycles function should return ~0x0fffffff but actually it returns
0xffffffff0fffffff.

That occurs because:

~(cycle_t)value is different from (cycle_t)~value.

unsigned long val = ~(unsigned long)0xf0000000;
40049a: 48 b8 ff ff ff 0f ff movabs $0xffffffff0fffffff,%rax

unsigned long val = (unsigned long)~0xf0000000;
40049a: 48 c7 45 f8 ff ff ff movq $0xfffffff,-0x8(%rbp)

We fix this issue by calculating bitwise-not counter, then cast to
cycle_t.

Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
drivers/clocksource/time-pistachio.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clocksource/time-pistachio.c b/drivers/clocksource/time-pistachio.c
index bba6799..3269d9e 100644
--- a/drivers/clocksource/time-pistachio.c
+++ b/drivers/clocksource/time-pistachio.c
@@ -84,7 +84,7 @@ pistachio_clocksource_read_cycles(struct clocksource *cs)
counter = gpt_readl(pcs->base, TIMER_CURRENT_VALUE, 0);
raw_spin_unlock_irqrestore(&pcs->lock, flags);

- return ~(cycle_t)counter;
+ return (cycle_t)~counter;
}

static u64 notrace pistachio_read_sched_clock(void)
--
1.9.1