Re: [PATCH v5 04/17] rtc: rzn1: Handle unset alarm weekday in rzn1_rtc_read_alarm

Hi Wolfram,

THank you for the review.

On Fri, Aug 21, 2026 at 4:08 PM Wolfram Sang
[off-list ref] wrote:

On Fri, Aug 21, 2026 at 02:55:55PM +0100, Prabhakar wrote:

quoted

From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>

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.

On a cold-booted board with no alarm configured, the following was
observed before the fix:

    root@rzn2h-evk:~# cat /proc/driver/rtc
    rtc_time        : 00:00:19
    rtc_date        : 2000-01-01
    alrm_time       : 00:00:00
    alrm_date       : 2000-01-07
    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

After the fix:

    root@rzn2h-evk:~# cat /proc/driver/rtc
    rtc_time        : 00:00:25
    rtc_date        : 2000-01-01
    alrm_time       : 00:00:00
    alrm_date       : 2000-01-01
    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

The output of the tests could be dropped IMO, but I'll leave this for
the RTC maintainers.

I'll drop it.

Cheers,
Prabhakar

quoted

Fixes: b5ad1bf00d2c4 ("rtc: rzn1: Add alarm support")
Cc: stable@vger.kernel.org
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>

Other than that:

Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>