Feature/zephyr compat/k timer isr dispatch

[swoisz]

Align ISR dispatch ability. Previously all k_timer backend cbs were in the esp_timer task ctx. This is more zephyr-like.

[Copilot]

Pull request overview

This PR makes Boreas’ k_timer behavior more Zephyr-compatible by optionally dispatching timer expiry callbacks in true ISR context (via ESP_TIMER_ISR) instead of the esp_timer task, and updates docs/examples/tests accordingly.

Changes:

• Add CONFIG_K_TIMER_DISPATCH_ISR (default y) and switch k_timer to use ESP_TIMER_ISR when enabled.
• Update internal users of k_timer (e.g., watchdog supervisor, delayable work, thread delayed start) to accommodate ISR-dispatch semantics.
• Add ISR-dispatch-focused unit tests and update the work-queue demo to defer logging out of ISR context.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
test/sdkconfig.defaults	Enables ISR-dispatch config for the test app.
test/main/test_k_timer.c	Adds ISR-dispatch validation tests and marks callbacks IRAM_ATTR.
examples/work_queue_demo/main/main.c	Demonstrates deferring timer ISR work to k_work before logging.
components/zsys/src/watchdog.c	Defers watchdog timer expiry work via k_work to avoid ISR-heavy logic.
components/zkernel/src/k_work.c	Marks delayable-work timer expiry callback IRAM_ATTR under ISR dispatch.
components/zkernel/src/k_timer.c	Switches esp_timer dispatch method to ISR when configured.
components/zkernel/src/k_thread.c	Adapts delayed thread start to safely resume from ISR-dispatched timer expiry.
components/zkernel/Kconfig	Introduces K_TIMER_DISPATCH_ISR option (default enabled).
components/zkernel/include/boreas/zephyr/kernel.h	Updates timer callback-context documentation; inlines user-data helpers.

Comments suppressed due to low confidence (1)

components/zkernel/src/k_work.c:342

• k_work_delayable_timer_expiry() is marked IRAM_ATTR under CONFIG_K_TIMER_DISPATCH_ISR, but it calls k_work_submit*/k_work_submit_to_queue, which are not IRAM_ATTR and may reside in flash. This undermines the stated “IRAM-only” requirement for ISR-dispatched timer callbacks and can crash when flash cache is disabled. Either ensure the work submission path (and its dependencies) is IRAM-safe under this config, or defer the submission to task context (e.g., via a pended function call).

#ifdef CONFIG_K_TIMER_DISPATCH_ISR
static void IRAM_ATTR k_work_delayable_timer_expiry(struct k_timer *timer)
#else
static void k_work_delayable_timer_expiry(struct k_timer *timer)
#endif
{
	struct k_work_delayable *dwork = CONTAINER_OF(timer, struct k_work_delayable, timer);
	if (dwork->queue) {
		k_work_submit_to_queue(dwork->queue, &dwork->work);
	} else {
		k_work_submit(&dwork->work);
	}
}

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[Copilot]

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 3 comments.

Comments suppressed due to low confidence (1)

components/zkernel/src/k_timer.c:88

• With ISR dispatch enabled, esp_timer_stop() does not wait for an in-flight callback to finish, but k_timer_start() proceeds to reset/update shared fields (status, first_interval_pending, is_periodic, period_us, etc.). This can race with k_timer_esp_callback() running on another core and, in particular, period_us is a non-atomic 64-bit value that may be torn. To match Zephyr’s restart/stop semantics safely under ESP_TIMER_ISR, add proper synchronization (e.g., a per-timer portMUX/spinlock used by both the ISR callback and start/stop paths, and/or an in_callback flag that start/stop waits out in task context).

	/* Stop any in-flight timer. With ESP_TIMER_TASK dispatch,
	 * esp_timer_stop blocks until the callback finishes; with
	 * ESP_TIMER_ISR dispatch it only removes the timer from the
	 * armed list (the ISR callback may still be executing on
	 * another core). Callers must not restart a timer whose
	 * callback is still running — same constraint as upstream Zephyr. */
	if (__atomic_load_n(&timer->running, __ATOMIC_ACQUIRE)) {
		esp_timer_stop(timer->handle);
	}

	__atomic_store_n(&timer->status, 0, __ATOMIC_RELAXED);
	__atomic_store_n(&timer->first_interval_pending, false, __ATOMIC_RELAXED);
	__atomic_store_n(&timer->is_periodic, !k_timeout_is_no_wait(period), __ATOMIC_RELEASE);

[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.