On Wed, Aug 19, 2026 at 11:39:24AM +0100, Prabhakar wrote: > From: Lad Prabhakar > > The RZ/N1 RTC driver selects SCMP mode only when an optional xtal clock > is provided at a valid rate other than 32768 Hz. Without an xtal clock, > or when it runs at 32768 Hz, the driver uses SUBU mode. > > However, the RTCA0SUBU register used by SUBU mode is not present on all > SoCs that integrate a similar variant of the RTC block. Allowing SUBU > mode on those variants would expose RTC offset operations that access a > non-existent register. > > Add OF match data to describe whether the RTC supports the SUBU register. > Reject probe with -EOPNOTSUPP when SUBU mode would be selected on a > variant without SUBU support. > > Signed-off-by: Lad Prabhakar Suggested-by: Wolfram Sang I still think, this code needs a change: 454 if (rate != 32768) 455 scmp_val = RZN1_RTC_CTL0_SLSB_SCMP; if (rate != 32768 || !data->has_subu) otherwise having a xtal with 32768 on a SCMP-only device will not be accepted despite it should work. Haven't checked if that could simplify your later has_subu-check or not.