Re: [PATCH v5 15/17] rtc: rzn1: Add OF match data to gate SUBU register access

Wolfram Sang <[email protected]>
Newsgroups org.kernel.vger.linux-rtc,org.kernel.vger.linux-devicetree,org.kernel.vger.linux-kernel,org.kernel.vger.linux-renesas-soc
Message-ID <aohr2--OFXSZQfXM@ninjato>
On Fri, Aug 21, 2026 at 02:56:06PM +0100, Prabhakar wrote:
> From: Lad Prabhakar <[email protected]>
> 
> 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 <[email protected]>
> Suggested-by: Wolfram Sang <[email protected]>

Reviewed-by: Wolfram Sang <[email protected]>
Tested-by: Wolfram Sang <[email protected]>
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