[PATCH 4.8 12/92] ARC: timer: rtc: implement read loop in "C" vs. inline asm

From: Greg Kroah-Hartman
Date: Thu Nov 17 2016 - 05:33:47 EST


4.8-stable review patch. If anyone has any objections, please let me know.

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

From: Vineet Gupta <vgupta@xxxxxxxxxxxx>

commit 922cc171998ac3dbe74d57011ef7ed57e9b0d7df upstream.

The current code doesn't even compile as somehow the inline assembly
can't see the register names defined as ARC_RTC_*
I'm pretty sure It worked when I first got it merged, but the tools were
definitely different then.

So better to write this in "C" anyways.

Acked-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
arch/arc/kernel/time.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)

--- a/arch/arc/kernel/time.c
+++ b/arch/arc/kernel/time.c
@@ -152,14 +152,17 @@ static cycle_t arc_read_rtc(struct clock
cycle_t full;
} stamp;

-
- __asm__ __volatile(
- "1: \n"
- " lr %0, [AUX_RTC_LOW] \n"
- " lr %1, [AUX_RTC_HIGH] \n"
- " lr %2, [AUX_RTC_CTRL] \n"
- " bbit0.nt %2, 31, 1b \n"
- : "=r" (stamp.low), "=r" (stamp.high), "=r" (status));
+ /*
+ * hardware has an internal state machine which tracks readout of
+ * low/high and updates the CTRL.status if
+ * - interrupt/exception taken between the two reads
+ * - high increments after low has been read
+ */
+ do {
+ stamp.low = read_aux_reg(AUX_RTC_LOW);
+ stamp.high = read_aux_reg(AUX_RTC_HIGH);
+ status = read_aux_reg(AUX_RTC_CTRL);
+ } while (!(status & _BITUL(31)));

return stamp.full;
}