6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Lad Prabhakar commit 457b5dbce31209e65e1184716ed3af59cb1c0372 upstream. 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 Reviewed-by: Wolfram Sang Tested-by: Wolfram Sang Link: https://patch.msgid.link/20260821211032.13554-5-prabhakar.mahadev-lad.rj@bp.renesas.com Signed-off-by: Alexandre Belloni Signed-off-by: Greg Kroah-Hartman --- drivers/rtc/rtc-rzn1.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) --- a/drivers/rtc/rtc-rzn1.c +++ b/drivers/rtc/rtc-rzn1.c @@ -235,13 +235,24 @@ static int rzn1_rtc_read_alarm(struct de if (ret) return ret; + ctl1 = readl(rtc->base + RZN1_RTC_CTL1); + alrm->enabled = !!(ctl1 & (RZN1_RTC_CTL1_ALME | RZN1_RTC_CTL1_1SE)); + min = readl(rtc->base + RZN1_RTC_ALM); hour = readl(rtc->base + RZN1_RTC_ALH); - wday = readl(rtc->base + RZN1_RTC_ALW); tm->tm_sec = 0; tm->tm_min = bcd2bin(min); tm->tm_hour = bcd2bin(hour); + + /* + * If wday is zero, no bit is set in RZN1_RTC_ALW. This is the + * register's power-on reset value. + */ + wday = readl(rtc->base + RZN1_RTC_ALW); + if (!wday) + return 0; + delta_days = ((fls(wday) - 1) - tm->tm_wday + 7) % 7; tm->tm_wday = fls(wday) - 1; @@ -250,9 +261,6 @@ static int rzn1_rtc_read_alarm(struct de rtc_time64_to_tm(alarm, tm); } - ctl1 = readl(rtc->base + RZN1_RTC_CTL1); - alrm->enabled = !!(ctl1 & (RZN1_RTC_CTL1_ALME | RZN1_RTC_CTL1_1SE)); - return 0; }