cyclic: Add basic support for cyclic function execution infrastruture

Add the basic infrastructure to periodically execute code, e.g. all
100ms. Examples for such functions might be LED blinking etc. The
functions that are hooked into this cyclic list should be small timewise
as otherwise the execution of the other code that relies on a high
frequent polling (e.g. UART rx char ready check) might be delayed too
much. This patch also adds the Kconfig option
CONFIG_CYCLIC_MAX_CPU_TIME_US, which configures the max allowed time
for such a cyclic function. If it's execution time exceeds this time,
this cyclic function will get removed from the cyclic list.

How is this cyclic functionality executed?
The following patch integrates the main function responsible for
calling all registered cyclic functions cyclic_run() into the
common WATCHDOG_RESET macro. This guarantees that cyclic_run() is
executed very often, which is necessary for the cyclic functions to
get scheduled and executed at their configured periods.

This cyclic infrastructure will be used by a board specific function on
the NIC23 MIPS Octeon board, which needs to check periodically, if a
PCIe FLR has occurred.

Signed-off-by: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>

1 files changed, 123 insertions, 0 deletions

diff --git a/common/cyclic.c b/common/cyclic.c
new file mode 100644
index 00000000000..cd5dcb1f2b9
--- /dev/null
+++ b/common/cyclic.c
@@ -0,0 +1,123 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * A general-purpose cyclic execution infrastructure, to allow "small"
+ * (run-time wise) functions to be executed at a specified frequency.
+ * Things like LED blinking or watchdog triggering are examples for such
+ * tasks.
+ *
+ * Copyright (C) 2022 Stefan Roese <sr@denx.de>
+ */
+
+#include <cyclic.h>
+#include <log.h>
+#include <malloc.h>
+#include <time.h>
+#include <linux/errno.h>
+#include <linux/list.h>
+#include <asm/global_data.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+struct list_head *cyclic_get_list(void)
+{
+	return &gd->cyclic->cyclic_list;
+}
+
+struct cyclic_info *cyclic_register(cyclic_func_t func, uint64_t delay_us,
+				    const char *name, void *ctx)
+{
+	struct cyclic_info *cyclic;
+
+	if (!gd->cyclic->cyclic_ready) {
+		pr_debug("Cyclic IF not ready yet\n");
+		return NULL;
+	}
+
+	cyclic = calloc(1, sizeof(struct cyclic_info));
+	if (!cyclic) {
+		pr_debug("Memory allocation error\n");
+		return NULL;
+	}
+
+	/* Store values in struct */
+	cyclic->func = func;
+	cyclic->ctx = ctx;
+	cyclic->name = strdup(name);
+	cyclic->delay_us = delay_us;
+	cyclic->start_time_us = timer_get_us();
+	list_add_tail(&cyclic->list, &gd->cyclic->cyclic_list);
+
+	return cyclic;
+}
+
+int cyclic_unregister(struct cyclic_info *cyclic)
+{
+	list_del(&cyclic->list);
+	free(cyclic);
+
+	return 0;
+}
+
+void cyclic_run(void)
+{
+	struct cyclic_info *cyclic, *tmp;
+	uint64_t now, cpu_time;
+
+	/* Prevent recursion */
+	if (gd->cyclic->cyclic_running)
+		return;
+
+	gd->cyclic->cyclic_running = true;
+	list_for_each_entry_safe(cyclic, tmp, &gd->cyclic->cyclic_list, list) {
+		/*
+		 * Check if this cyclic function needs to get called, e.g.
+		 * do not call the cyclic func too often
+		 */
+		now = timer_get_us();
+		if (time_after_eq64(now, cyclic->next_call)) {
+			/* Call cyclic function and account it's cpu-time */
+			cyclic->next_call = now + cyclic->delay_us;
+			cyclic->func(cyclic->ctx);
+			cyclic->run_cnt++;
+			cpu_time = timer_get_us() - now;
+			cyclic->cpu_time_us += cpu_time;
+
+			/* Check if cpu-time exceeds max allowed time */
+			if (cpu_time > CONFIG_CYCLIC_MAX_CPU_TIME_US) {
+				pr_err("cyclic function %s took too long: %lldus vs %dus max, disabling\n",
+				       cyclic->name, cpu_time,
+				       CONFIG_CYCLIC_MAX_CPU_TIME_US);
+
+				/* Unregister this cyclic function */
+				cyclic_unregister(cyclic);
+			}
+		}
+	}
+	gd->cyclic->cyclic_running = false;
+}
+
+int cyclic_uninit(void)
+{
+	struct cyclic_info *cyclic, *tmp;
+
+	list_for_each_entry_safe(cyclic, tmp, &gd->cyclic->cyclic_list, list)
+		cyclic_unregister(cyclic);
+	gd->cyclic->cyclic_ready = false;
+
+	return 0;
+}
+
+int cyclic_init(void)
+{
+	int size = sizeof(struct cyclic_drv);
+
+	gd->cyclic = (struct cyclic_drv *)malloc(size);
+	if (!gd->cyclic)
+		return -ENOMEM;
+
+	memset(gd->cyclic, '\0', size);
+	INIT_LIST_HEAD(&gd->cyclic->cyclic_list);
+	gd->cyclic->cyclic_ready = true;
+
+	return 0;
+}