rtc: rzn1: Handle unset alarm weekday in rzn1_rtc_read_alarm

RZN1_RTC_ALW is a weekday bitmask where bit N represents weekday N.
When no alarm has been configured, the register has its power-on-reset
value of zero.

rzn1_rtc_read_alarm() uses fls() to convert the weekday bitmask into a
weekday number. When RZN1_RTC_ALW is zero, fls(0) returns zero and
fls(wday) - 1 evaluates to -1. This invalid weekday is then used to
calculate the alarm date and can either leave tm_wday set to -1 or
produce a fabricated alarm date.

Treat a zero RZN1_RTC_ALW value as an unset alarm weekday and return
without calculating the alarm date. Move reading RZN1_RTC_CTL1 before
this check so that alrm->enabled is updated for both configured and
unconfigured alarms.

Fixes: b5ad1bf00d2c4 ("rtc: rzn1: Add alarm support")
Cc: stable@vger.kernel.org
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://patch.msgid.link/20260821211032.13554-5-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

0 files changed, 0 insertions, 0 deletions