cyclic: get rid of cyclic_init()

Currently, we must call cyclic_init() at some point before
cyclic_register() becomes possible. That turns out to be somewhat
awkward, especially with SPL, and has resulted in a watchdog callback
not being registered, thus causing the board to prematurely reset.

We already rely on gd->cyclic reliably being set to NULL by the asm
code that clears all of gd. Now that the cyclic list is a hlist, and
thus an empty list is represented by a NULL head pointer, and struct
cyclic_drv has no other members, we can just as well drop a level of
indirection and put the hlist_head directly in struct
global_data. This doesn't increase the size of struct global_data,
gets rid of an early malloc(), and generates slightly smaller code.

But primarily, this avoids having to call cyclic_init() early; the cyclic
infrastructure is simply ready to register callbacks as soon as we
enter C code.

We can still end up with schedule() being called from asm very early,
so we still need to check that gd itself has been properly initialized
[*], but once it has, gd->cyclic_list is perfectly fine to access, and
will just be an empty list.

As for cyclic_uninit(), it was never really the opposite of
cyclic_init() since it didn't free the struct cyclic_drv nor set
gd->cyclic to NULL. Rename it to cyclic_unregister_all() and use that
in test/, and also insert a call at the end of the board_init_f
sequence so that gd->cyclic_list is a fresh empty list before we enter
board_init_r().

A small piece of ugliness is that I had to add a cast in
cyclic_get_list() to silence a "discards 'volatile' qualifier"
warning, but that is completely equivalent to the existing handling of
the uclass_root_s list_head member.

[*] I'm not really sure where we guarantee that the register used for
gd contains 0 until it gets explicitly initialized, but that must be
the case, otherwise testing gd for being NULL would not make much sense.

Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-by: Stefan Roese <sr@denx.de>
Tested-by: Tim Harvey <tharvey@gateworks.com> # imx8mm-venice-*

common/board_f.c

@@ -839,7 +839,6 @@ static const init_fnc_t init_sequence_f[] = {
 	initf_malloc,
 	log_init,
 	initf_bootstage,	/* uses its own timer, so does not need DM */
-	cyclic_init,
 	event_init,
 #ifdef CONFIG_BLOBLIST
 	bloblist_init,
@@ -957,6 +956,16 @@ static const init_fnc_t init_sequence_f[] = {
 	do_elf_reloc_fixups,
 #endif
 	clear_bss,
+	/*
+	 * Deregister all cyclic functions before relocation, so that
+	 * gd->cyclic_list does not contain any references to pre-relocation
+	 * devices. Drivers will register their cyclic functions anew when the
+	 * devices are probed again.
+	 *
+	 * This should happen as late as possible so that the window where a
+	 * watchdog device is not serviced is as small as possible.
+	 */
+	cyclic_unregister_all,
 #if !defined(CONFIG_ARM) && !defined(CONFIG_SANDBOX) && \
 		!CONFIG_IS_ENABLED(X86_64)
 	jump_to_copy,

common/board_r.c

@@ -617,7 +617,6 @@ static init_fnc_t init_sequence_r[] = {
 #endif
 	initr_barrier,
 	initr_malloc,
-	cyclic_init,
 	log_init,
 	initr_bootstage,	/* Needs malloc() but has its own timer */
 #if defined(CONFIG_CONSOLE_RECORD)

common/cyclic.c

@@ -22,7 +22,8 @@ void hw_watchdog_reset(void);
 
 struct hlist_head *cyclic_get_list(void)
 {
-	return &gd->cyclic->cyclic_list;
+	/* Silence "discards 'volatile' qualifier" warning. */
+	return (struct hlist_head *)&gd->cyclic_list;
 }
 
 struct cyclic_info *cyclic_register(cyclic_func_t func, uint64_t delay_us,
@@ -30,11 +31,6 @@ struct cyclic_info *cyclic_register(cyclic_func_t func, uint64_t delay_us,
 {
 	struct cyclic_info *cyclic;
 
-	if (!gd->cyclic) {
-		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");
@@ -47,7 +43,7 @@ struct cyclic_info *cyclic_register(cyclic_func_t func, uint64_t delay_us,
 	cyclic->name = strdup(name);
 	cyclic->delay_us = delay_us;
 	cyclic->start_time_us = timer_get_us();
-	hlist_add_head(&cyclic->list, &gd->cyclic->cyclic_list);
+	hlist_add_head(&cyclic->list, cyclic_get_list());
 
 	return cyclic;
 }
@@ -71,7 +67,7 @@ void cyclic_run(void)
 		return;
 
 	gd->flags |= GD_FLG_CYCLIC_RUNNING;
-	hlist_for_each_entry_safe(cyclic, tmp, &gd->cyclic->cyclic_list, list) {
+	hlist_for_each_entry_safe(cyclic, tmp, cyclic_get_list(), list) {
 		/*
 		 * Check if this cyclic function needs to get called, e.g.
 		 * do not call the cyclic func too often
@@ -113,31 +109,17 @@ void schedule(void)
 	 * schedule() might get called very early before the cyclic IF is
 	 * ready. Make sure to only call cyclic_run() when it's initalized.
 	 */
-	if (gd && gd->cyclic)
+	if (gd)
 		cyclic_run();
 }
 
-int cyclic_uninit(void)
+int cyclic_unregister_all(void)
 {
 	struct cyclic_info *cyclic;
 	struct hlist_node *tmp;
 
-	hlist_for_each_entry_safe(cyclic, tmp, &gd->cyclic->cyclic_list, list)
+	hlist_for_each_entry_safe(cyclic, tmp, cyclic_get_list(), list)
 		cyclic_unregister(cyclic);
 
 	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_HLIST_HEAD(&gd->cyclic->cyclic_list);
-
-	return 0;
-}

include/asm-generic/global_data.h

@@ -481,9 +481,9 @@ struct global_data {
 #endif
 #ifdef CONFIG_CYCLIC
 	/**
-	 * @cyclic: cyclic driver data
+	 * @cyclic_list: list of registered cyclic functions
 	 */
-	struct cyclic_drv *cyclic;
+	struct hlist_head cyclic_list;
 #endif
 	/**
 	 * @dmtag_list: List of DM tags

include/cyclic.h

@@ -14,15 +14,6 @@
 #include <linux/list.h>
 #include <asm/types.h>
 
-/**
- * struct cyclic_drv - Cyclic driver internal data
- *
- * @cyclic_list: Cylic list node
- */
-struct cyclic_drv {
-	struct hlist_head cyclic_list;
-};
-
 /**
  * struct cyclic_info - Information about cyclic execution function
  *
@@ -75,18 +66,11 @@ struct cyclic_info *cyclic_register(cyclic_func_t func, uint64_t delay_us,
 int cyclic_unregister(struct cyclic_info *cyclic);
 
 /**
- * cyclic_init() - Set up cyclic functions
- *
- * Init a list of cyclic functions, so that these can be added as needed
- */
-int cyclic_init(void);
-
-/**
- * cyclic_uninit() - Clean up cyclic functions
+ * cyclic_unregister_all() - Clean up cyclic functions
  *
  * This removes all cyclic functions
  */
-int cyclic_uninit(void);
+int cyclic_unregister_all(void);
 
 /**
  * cyclic_get_list() - Get cyclic list pointer
@@ -134,12 +118,7 @@ static inline void schedule(void)
 {
 }
 
-static inline int cyclic_init(void)
-{
-	return 0;
-}
-
-static inline int cyclic_uninit(void)
+static inline int cyclic_unregister_all(void)
 {
 	return 0;
 }

test/test-main.c

@@ -287,7 +287,6 @@ static int dm_test_restore(struct device_node *of_root)
 static int test_pre_run(struct unit_test_state *uts, struct unit_test *test)
 {
 	ut_assertok(event_init());
-	ut_assertok(cyclic_init());
 
 	if (test->flags & UT_TESTF_DM)
 		ut_assertok(dm_test_pre_run(uts));
@@ -347,7 +346,7 @@ static int test_post_run(struct unit_test_state *uts, struct unit_test *test)
 	ut_unsilence_console(uts);
 	if (test->flags & UT_TESTF_DM)
 		ut_assertok(dm_test_post_run(uts));
-	ut_assertok(cyclic_uninit());
+	ut_assertok(cyclic_unregister_all());
 	ut_assertok(event_uninit());
 
 	free(uts->of_other);