Add RTC support for Renesas RZ/T2H and RZ/N2H SoCs

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

Hi all,

This series adds support for the RTC IP found on the Renesas RZ/T2H and
RZ/N2H SoCs.

The RTC block is closely related to the RZ/N1 implementation and can
reuse the existing driver infrastructure when operating in SCMP mode,
which is required on these SoCs due to their 195.3 kHz RTC input clock.

While the RZ/T2H and RZ/N2H variants do not implement the RTCA0SUBU
register present on RZ/N1, this register is not accessed by the driver
in SCMP mode, allowing support to be added with minimal changes.

The RZ/T2H RTC variant also supports a 1 Hz output signal on the
RTCAT1HZ pin, controlled by the RTCA0CTL1[RTCA01HZE] bit. This bit is
marked as reserved in the RZ/N1 hardware manual, making RZ/T2H a
distinct RTC variant despite its overall compatibility with the RZ/N1
implementation.

Patches have been rebased on top of next-20260630.

Test Logs:
----------
#rtctest
root@rzn2h-evk:~# rtctest
TAP version 13
1..8
# Starting 8 tests from 1 test cases.
#  RUN           rtc.date_read ...
# rtctest.c:59:date_read:Current RTC date/time is 01/01/2000 00:03:09.
#            OK  rtc.date_read
ok 1 rtc.date_read
#  RUN           rtc.date_read_loop ...
# rtctest.c:124:date_read_loop:Continuously reading RTC time for 30s (with 11ms
# rtctest.c:151:date_read_loop:Performed 2790 RTC time reads.
#            OK  rtc.date_read_loop
ok 2 rtc.date_read_loop
#  RUN           rtc.uie_read ...
#            OK  rtc.uie_read
ok 3 rtc.uie_read
#  RUN           rtc.uie_select ...
#            OK  rtc.uie_select
ok 4 rtc.uie_select
#  RUN           rtc.alarm_alm_set ...
# rtctest.c:262:alarm_alm_set:Alarm time now set to 00:03:49.
# rtctest.c:282:alarm_alm_set:data: 1a0
#            OK  rtc.alarm_alm_set
ok 5 rtc.alarm_alm_set
#  RUN           rtc.alarm_wkalm_set ...
# rtctest.c:334:alarm_wkalm_set:Alarm time now set to 01/01/2000 00:03:52.
#            OK  rtc.alarm_wkalm_set
ok 6 rtc.alarm_wkalm_set
#  RUN           rtc.alarm_alm_set_minute ...
# rtctest.c:394:alarm_alm_set_minute:Alarm time now set to 00:04:00.
# rtctest.c:414:alarm_alm_set_minute:data: 1a0
#            OK  rtc.alarm_alm_set_minute
ok 7 rtc.alarm_alm_set_minute
#  RUN           rtc.alarm_wkalm_set_minute ...
# rtctest.c:464:alarm_wkalm_set_minute:Alarm time now set to 01/01/2000 00:05:00
#            OK  rtc.alarm_wkalm_set_minute
ok 8 rtc.alarm_wkalm_set_minute
# PASSED: 8 / 8 tests passed.
# Totals: pass:8 fail:0 xfail:0 xpass:0 skip:0 error:0
root@rzn2h-evk:~#
root@rzn2h-evk:~#

#Alarm for next day
root@rzn2h-evk:~# date -s "2026-07-01 12:45:00"; hwclock -w;
Wed Jul  1 12:45:00 UTC 2026
root@rzn2h-evk:~# rtcwake -m no -s 86400;cat /proc/driver/rtc
rtcwake: wakeup using /dev/rtc0 at Thu Jul  2 12:45:35 2026
rtc_time        : 12:45:34
rtc_date        : 2026-07-01
alrm_time       : 12:45:35
alrm_date       : 2026-07-02
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:~#

#Alarm for next week
root@rzn2h-evk:~# rtcwake -m no -s 604799;cat /proc/driver/rtc
rtcwake: wakeup using /dev/rtc0 at Wed Jul  8 12:47:38 2026
rtc_time        : 12:47:38
rtc_date        : 2026-07-01
alrm_time       : 12:47:38
alrm_date       : 2026-07-08
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:~#

v1->v2:
- Dropped wakeup capability support patch.
- Dropped header sort patch as it was already fixed upstream.
- Updated commit message to drop reference about RTCA0TCR register.
- Added Acked-by and Reviewed-by tags.
- Updated Kconfig help text to keep it generic and not specific to
  RZ/N1 SoCs.
- Initialized rate variable to 32768 to avoid timeout_us of 0.
- Made use of RZN1_RTC_SUBU_RTCA0FX mask for SUBU register access
  instead of 0x3F.

v1: https://lore.kernel.org/all/20260615154805.1619693-1-prab...

Cheers,
Prabhakar

Lad Prabhakar (10):
  dt-bindings: rtc: renesas,rzn1-rtc: Add RZ/T2H and RZ/N2H support
  rtc: rzn1: Handle EPROBE_DEFER for optional pps interrupt
  rtc: rzn1: Fix malformed MODULE_AUTHOR string
  rtc: Kconfig: Broaden RTC_DRV_RZN1 dependency to ARCH_RENESAS
  rtc: rzn1: Fix alarm range check truncation on 32-bit systems
  rtc: rzn1: Dynamically calculate synchronization delay based on clock
    rate
  rtc: rzn1: Use temporary variable for struct device
  rtc: rzn1: Consistently use dev_err_probe()
  rtc: rzn1: use FIELD_PREP/FIELD_GET and GENMASK for register access
  rtc: rzn1: Add support for Renesas RZ/T2H and RZ/N2H SoCs

 .../bindings/rtc/renesas,rzn1-rtc.yaml        |  35 ++++--
 drivers/rtc/Kconfig                           |   5 +-
 drivers/rtc/rtc-rzn1.c                        | 104 +++++++++++-------
 3 files changed, 94 insertions(+), 50 deletions(-)

-- 
2.54.0