rtc: rzn1: Fix weekday underflow when alarm crosses month boundary

rzn1_rtc_set_alarm() calculates the alarm weekday from the difference
between the alarm day and the current day of the month. When the alarm
crosses a month boundary, this difference can become negative. Since
days_ahead is unsigned, it underflows and results in an incorrect
weekday being programmed into RZN1_RTC_ALW.

The RTC core already provides a fully populated struct rtc_time for
the alarm, including the correct tm_wday. Use tm->tm_wday directly
instead of recalculating the weekday from the day-of-month.

This avoids the underflow and ensures alarms scheduled across a month
boundary use the correct weekday.

Fixes: b5ad1bf00d2c4 ("rtc: rzn1: Add alarm support")
Cc: stable@vger.kernel.org
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Suggested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://patch.msgid.link/20260821211032.13554-4-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

0 files changed, 0 insertions, 0 deletions