Re: [PATCH v4 09/15] rtc: rzn1: Dynamically calculate synchronization delay based on clock rate

Wolfram Sang <[email protected]> Wed, 19 Aug 2026 15:08:21 +0200

Newsgroups	org.kernel.vger.linux-renesas-soc,org.kernel.vger.linux-devicetree,org.kernel.vger.linux-kernel,org.kernel.vger.linux-rtc
Message-ID	<aoWqxdIpvTP8zoOX@shikoro>

On Wed, Aug 19, 2026 at 11:39:20AM +0100, Prabhakar wrote:
> From: Lad Prabhakar <[email protected]>
> 
> Replace the hardcoded hardware synchronization delays with a calculated
> time window derived from the operating sub-clock frequency.
> 
> The driver currently hardcodes microsecond ranges assuming a fixed
> sub-clock frequency of 32.768 kHz. Newer SoC variants, such as the
> RZ/T2H, drive this hardware block using a much faster clock rate
> (~195.3 kHz). Hardcoding these wait windows forces faster blocks to
> over-sleep, introducing unnecessary delays during clock initialization
> and register configuration.
> 
> Calculate the duration of the required clock cycles in microseconds based
> on the runtime clock rate, and store this value in the driver private
> structure to adjust the usleep_range() and readl_poll_timeout() boundaries
> dynamically.
> 
> Signed-off-by: Lad Prabhakar <[email protected]>

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

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