[PATCH v4 5/5] rtc: zynqmp: use dynamic max and min offset ranges

[Tomas Melin]

Maximum and minimum offsets in ppb that can be handled are dependent on
the rtc clock frequency and what can fit in the 16-bit register field.

Reviewed-by: Harini T <harini.t at amd.com>
Tested-by: Harini T <harini.t at amd.com>
Signed-off-by: Tomas Melin <tomas.melin at vaisala.com>
---
 drivers/rtc/rtc-zynqmp.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/rtc/rtc-zynqmp.c b/drivers/rtc/rtc-zynqmp.c
index f0f5dc63e254799ed99927c259c767b30ee877a4..2ae54804b87a47642d118789dc33191c53b36932 100644
--- a/drivers/rtc/rtc-zynqmp.c
+++ b/drivers/rtc/rtc-zynqmp.c
@@ -44,8 +44,6 @@
 #define RTC_FR_MASK		0xF0000
 #define RTC_FR_MAX_TICKS	16
 #define RTC_PPB			1000000000
-#define RTC_MIN_OFFSET		-32768000
-#define RTC_MAX_OFFSET		32767000
 
 struct xlnx_rtc_dev {
 	struct rtc_device	*rtc;
@@ -215,12 +213,13 @@ static int xlnx_rtc_set_offset(struct device *dev, long offset)
 
 	/* Tick to offset multiplier */
 	tick_mult = DIV_ROUND_CLOSEST(RTC_PPB, freq);
-	if (offset < RTC_MIN_OFFSET || offset > RTC_MAX_OFFSET)
-		return -ERANGE;
 
 	/* Number ticks for given offset */
 	max_tick = div_s64_rem(offset, tick_mult, &fract_offset);
 
+	if (freq + max_tick > RTC_TICK_MASK || (freq + max_tick < 1))
+		return -ERANGE;
+
 	/* Number fractional ticks for given offset */
 	if (fract_offset) {
 		fract_part = DIV_ROUND_UP(tick_mult, RTC_FR_MAX_TICKS);

-- 
2.47.3