[PATCH v2 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.

Signed-off-by: Tomas Melin <tomas.melin at vaisala.com>
---
 drivers/rtc/rtc-zynqmp.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/rtc/rtc-zynqmp.c b/drivers/rtc/rtc-zynqmp.c
index d15c256e7ae56058ddc38849af6424cd29b8965e..f508c61f4046e906d9569cc779a1360474a85fd2 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			1000000000LL
-#define RTC_MIN_OFFSET		-32768000
-#define RTC_MAX_OFFSET		32767000
 
 struct xlnx_rtc_dev {
 	struct rtc_device	*rtc;
@@ -215,12 +213,12 @@ static int xlnx_rtc_set_offset(struct device *dev, long offset)
 
 	/* Tick to offset multiplier */
 	tick_mult = DIV_ROUND_CLOSEST(RTC_PPB, xrtcdev->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