On Fri, Aug 21, 2026 at 02:56:06PM +0100, Prabhakar wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> 
> 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 <prabhakar.mahadev-lad.rj@bp.renesas.com>
> Suggested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

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