[PATCHv4] clocksource: dw_apb_timer_of: Fix read_sched_clock

[<dinguyen@altera.com>]

From: Dinh Nguyen <dinguyen@altera.com>

The read_sched_clock should return the ~value because the clock is a
countdown implementation. read_sched_clock() should be the same as
__apbt_read_clocksource().

Maintain backwards compatibility for "dw-apb-timer-sp" and
"dw-apb-timer-osc".

Signed-off-by: Dinh Nguyen <dinguyen@altera.com>
---
v4: Simplify the fix by simply returning ~__raw_readl(sched_io_base)
v3: Use APBTMR_N_CURRENT_VALUE define in read_sched_clock()
v2: Maintain backwards compatibility for "dw-apb-timer-sp" and
      "dw-apb-timer-osc".
---
 drivers/clocksource/dw_apb_timer_of.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/clocksource/dw_apb_timer_of.c b/drivers/clocksource/dw_apb_timer_of.c
index 45ba8ae..8d6e5f6 100644
--- a/drivers/clocksource/dw_apb_timer_of.c
+++ b/drivers/clocksource/dw_apb_timer_of.c
@@ -108,12 +108,11 @@ static void __init add_clocksource(struct device_node *source_timer)
 
 static u64 read_sched_clock(void)
 {
-	return __raw_readl(sched_io_base);
+	return ~__raw_readl(sched_io_base);
 }
 
 static const struct of_device_id sptimer_ids[] __initconst = {
 	{ .compatible = "picochip,pc3x2-rtc" },
-	{ .compatible = "snps,dw-apb-timer-sp" },
 	{ /* Sentinel */ },
 };
 
@@ -151,4 +150,7 @@ static void __init dw_apb_timer_init(struct device_node *timer)
 	num_called++;
 }
 CLOCKSOURCE_OF_DECLARE(pc3x2_timer, "picochip,pc3x2-timer", dw_apb_timer_init);
-CLOCKSOURCE_OF_DECLARE(apb_timer, "snps,dw-apb-timer-osc", dw_apb_timer_init);
+CLOCKSOURCE_OF_DECLARE(apb_timer_osc, "snps,dw-apb-timer-osc", dw_apb_timer_init);
+CLOCKSOURCE_OF_DECLARE(apb_timer_sp, "snps,dw-apb-timer-sp", dw_apb_timer_init);
+CLOCKSOURCE_OF_DECLARE(apb_timer, "snps,dw-apb-timer", dw_apb_timer_init);
+
-- 
1.7.9.5