kernel/timer: fix period argument clamp handling

Commit 3e729b2b1c52 ("kernel/timer: Correctly clamp period argument")
increased the lower limit to 1 so that it wouldn't conflict with a
K_NO_WAIT. But in doing so it enforced a minimum period of 2 ticks.
And the subtraction must obviously be avoided if the period is zero, etc.

Instead of doing this masquerade in k_timer_start(), let's move the
subtraction and clamping in z_timer_expiration_handler() right before
registering a new timeout. It makes the code cleaner, and then it is
possible to have single-tick periods again.

Whith this, timer_jitter_drift in tests/kernel/timer/timer_behavior does
pass with any CONFIG_SYS_CLOCK_TICKS_PER_SEC value, even when the tick
period is equal or larger than the specified timer period for the test
which failed the test before.

Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
1 file changed