Hi Wolfram, Thank you for the review. On Fri, Aug 1, 2025 at 5:10 AM Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Tue, Jul 29, 2025 at 04:59:13PM +0100, Prabhakar wrote: > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx> > > > > Update the watchdog minimum timeout value to be derived from > > `max_hw_heartbeat_ms` using `DIV_ROUND_UP()` to ensure a valid and > > consistent minimum timeout in seconds. > > I don't understand this change. Why is the _minimum_ timeout based on > the _maximum_ heartbeat? > The reason for deriving min_timeout from max_hw_heartbeat_ms is to ensure the minimum watchdog period (in seconds) is compatible with the underlying hardware. max_hw_heartbeat_ms is calculated as: max_hw_heartbeat_ms = (1000 * 16384 * cks_div) / clk_rate; This value varies by SoC: RZ/T2H: cks_div = 8192, clk ≈ 62.5 MHz -> max_hw_heartbeat_ms ~ 2147ms RZ/V2H: cks_div = 256, clk ≈ 240 MHz -> max_hw_heartbeat_ms ~ 174ms Since min_timeout is in seconds, setting it to: min_timeout = DIV_ROUND_UP(max_hw_heartbeat_ms, 1000); ensures: The minimum timeout period is never less than what the hardware can support. - For T2H, this results in a min_timeout of 3s (2147ms -> 3s). - For V2H, it’s just 1s (174ms -> 1s). Cheers, Prabhakar
