Re: [PATCH 07/12] rtc: rzn1: fix alarm range check truncation on 32-bit systems

[Lad, Prabhakar]

Hi Wolfram,

On Tue, Jun 23, 2026 at 10:08 PM Wolfram Sang
<wsa+renesas@xxxxxxxxxxxxxxxxxxxx> wrote:
>
>
> > Can you please share the commands you tried, I'll try and replicate it
> > on my side.
>
> Sorry, can't give you the commands, just from my head: I tried to set an
> alarm more than a week in the future, and the alarm was set to the next
> day. But I was in a hurry, maybe I overlooked something, because that
> handling used to work in the past IIRC. I can return to this topic on
> Friday earliest, sadly. Maybe next week only...
>
I ran some tests for cases #1 and #2, and we see an out-of-range
error. By adding a 1-sec leeway when checking the ranges I don't get
the out-of-range error. Let me know what you think (I'll create a
seprate patch for it).

Case #1 reverting this patch:

root@rzn2h-evk:~# date -s "2026-06-24 10:34:00"; hwclock -w;
Wed Jun 24 10:34:00 UTC 2026
root@rzn2h-evk:~#
root@rzn2h-evk:~#
root@rzn2h-evk:~# rtcwake -m no -s 604800;cat /proc/driver/rtc
rtcwake: set rtc wake alarm failed: Numerical result out of range
rtc_time        : 10:34:32
rtc_date        : 2026-06-24
alrm_time       : 10:34:33
alrm_date       : 2026-07-01
alarm_IRQ       : no
alrm_pending    : no
update IRQ enabled      : no
periodic IRQ enabled    : no
periodic IRQ frequency  : 1
max user IRQ frequency  : 64
24hr            : yes
root@rzn2h-evk:~#

Case #2 with this patch:
root@rzn2h-evk:~# date -s "2026-06-24 10:46:00"; hwclock -w;
Wed Jun 24 10:46:00 UTC 2026
root@rzn2h-evk:~# rtcwake -m no -s 604800;cat /proc/driver/rtc
rtcwake: set rtc wake alarm failed: Numerical result out of range
rtc_time        : 10:46:30
rtc_date        : 2026-06-24
alrm_time       : 10:46:31
alrm_date       : 2026-07-01
alarm_IRQ       : no
alrm_pending    : no
update IRQ enabled      : no
periodic IRQ enabled    : no
periodic IRQ frequency  : 1
max user IRQ frequency  : 64
24hr            : yes
root@rzn2h-evk:~#

Case #3: Add 1-sec  leeway:
root@rzn2h-evk:~# date -s "2026-06-24 10:48:00"; hwclock -w;
Wed Jun 24 10:48:00 UTC 2026
root@rzn2h-evk:~# rtcwake -m no -s 604800;cat /proc/driver/rtc
rtcwake: wakeup using /dev/rtc0 at Wed Jul  1 10:48:50 2026
rtc_time        : 10:48:49
rtc_date        : 2026-06-24
alrm_time       : 10:48:50
alrm_date       : 2026-07-01
alarm_IRQ       : yes
alrm_pending    : no
update IRQ enabled      : no
periodic IRQ enabled    : no
periodic IRQ frequency  : 1
max user IRQ frequency  : 64
24hr            : yes
root@rzn2h-evk:~#


Changes for case #3:

diff --git a/drivers/rtc/rtc-rzn1.c b/drivers/rtc/rtc-rzn1.c
index 173526d50d41..8fdb5114a6d8 100644
--- a/drivers/rtc/rtc-rzn1.c
+++ b/drivers/rtc/rtc-rzn1.c
@@ -279,7 +279,9 @@ static int rzn1_rtc_set_alarm(struct device *dev,
struct rtc_wkalrm *alrm)
        /* We cannot set alarms more than one week ahead */
        farest = rtc_tm_to_time64(&tm_now) + rtc->rtcdev->alarm_offset_max;
        alarm = rtc_tm_to_time64(tm);
-       if (alarm > farest)
+
+       /* Add a 1-second leeway for processing delay */
+       if (alarm > (farest + 1))
                return -ERANGE;

        /* Convert alarm day into week day */


Cheers,
Prabhakar