[PATCH v5 05/13] hw/core/resettable: add support for changing parent

[Damien Hedde <damien.hedde@greensocs.com>]

Add a function resettable_change_parent() to do the required
plumbing when changing the parent a of Resettable object.

We need to make sure that the reset state of the object remains
coherent with the reset state of the new parent.

We make the 2 following hypothesis:
+ when an object is put in a parent under reset, the object goes in
reset.
+ when an object is removed from a parent under reset, the object
leaves reset.

The added function avoid any glitch if both old and new parent are
already in reset.

Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
---
 hw/core/resettable.c    | 54 +++++++++++++++++++++++++++++++++++++++++
 hw/core/trace-events    |  1 +
 include/hw/resettable.h | 16 ++++++++++++
 3 files changed, 71 insertions(+)

diff --git a/hw/core/resettable.c b/hw/core/resettable.c
index c5e11cff4f..60d4285fcc 100644
--- a/hw/core/resettable.c
+++ b/hw/core/resettable.c
@@ -32,6 +32,14 @@ static void resettable_phase_exit(Object *obj, void *opaque, ResetType type);
  */
 static bool enter_phase_in_progress;
 
+/**
+ * exit_phase_in_progress:
+ * Flag telling whether we are currently in an enter phase where side
+ * effects are forbidden. This flag allows us to catch if
+ * resettable_change_parent() is called during exit phase.
+ */
+static unsigned exit_phase_in_progress;
+
 void resettable_reset(Object *obj, ResetType type)
 {
     trace_resettable_reset(obj, type);
@@ -58,7 +66,9 @@ void resettable_release_reset(Object *obj, ResetType type)
     /* TODO: change that assert when adding support for other reset types */
     assert(type == RESET_TYPE_COLD);
     trace_resettable_reset_release_begin(obj, type);
+    exit_phase_in_progress += 1;
     resettable_phase_exit(obj, NULL, type);
+    exit_phase_in_progress -= 1;
     trace_resettable_reset_release_end(obj);
 }
 
@@ -198,6 +208,50 @@ static void resettable_phase_exit(Object *obj, void *opaque, ResetType type)
     trace_resettable_phase_exit_end(obj, obj_typename, s->count);
 }
 
+/*
+ * resettable_get_count:
+ * Get the count of the Resettable object @obj. Return 0 if @obj is NULL.
+ */
+static uint32_t resettable_get_count(Object *obj)
+{
+    if (obj) {
+        ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
+        return rc->get_state(obj)->count;
+    }
+    return 0;
+}
+
+void resettable_change_parent(Object *obj, Object *newp, Object *oldp)
+{
+    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
+    ResettableState *s = rc->get_state(obj);
+    uint32_t newp_count = resettable_get_count(newp);
+    uint32_t oldp_count = resettable_get_count(oldp);
+
+    assert(!enter_phase_in_progress && !exit_phase_in_progress);
+    trace_resettable_change_parent(obj, oldp, oldp_count, newp, newp_count);
+
+    /*
+     * At most one of the two 'for' loop will be executed below
+     * in order to cope with the diff between the two count.
+     */
+    /* if newp is more reset than oldp */
+    for (uint32_t i = oldp_count; i < newp_count; i++) {
+        resettable_assert_reset(obj, RESET_TYPE_COLD);
+    }
+    /*
+     * if obj is leaving a bus under reset, we need to ensure
+     * hold phase is not pending.
+     */
+    if (oldp_count && s->hold_phase_pending) {
+        resettable_phase_hold(obj, NULL, RESET_TYPE_COLD);
+    }
+    /* if oldp is more reset than newp */
+    for (uint32_t i = newp_count; i < oldp_count; i++) {
+        resettable_release_reset(obj, RESET_TYPE_COLD);
+    }
+}
+
 void resettable_class_set_parent_phases(ResettableClass *rc,
                                         ResettableEnterPhase enter,
                                         ResettableHoldPhase hold,
diff --git a/hw/core/trace-events b/hw/core/trace-events
index 66081d0fb4..6d03ef7ff9 100644
--- a/hw/core/trace-events
+++ b/hw/core/trace-events
@@ -16,6 +16,7 @@ resettable_reset_assert_begin(void *obj, int cold) "obj=%p cold=%d"
 resettable_reset_assert_end(void *obj) "obj=%p"
 resettable_reset_release_begin(void *obj, int cold) "obj=%p cold=%d"
 resettable_reset_release_end(void *obj) "obj=%p"
+resettable_change_parent(void *obj, void *o, uint32_t oc, void *n, uint32_t nc) "obj=%p from=%p(%" PRIu32 ") to=%p(%" PRIu32 ")"
 resettable_phase_enter_begin(void *obj, const char *objtype, uint32_t count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
 resettable_phase_enter_exec(void *obj, const char *objtype, int type, int has_method) "obj=%p(%s) type=%d method=%d"
 resettable_phase_enter_end(void *obj, const char *objtype, uint32_t count) "obj=%p(%s) count=%" PRIu32
diff --git a/include/hw/resettable.h b/include/hw/resettable.h
index 6b24e1633b..f6d379669f 100644
--- a/include/hw/resettable.h
+++ b/include/hw/resettable.h
@@ -182,6 +182,22 @@ void resettable_release_reset(Object *obj, ResetType type);
  */
 bool resettable_is_in_reset(Object *obj);
 
+/**
+ * resettable_change_parent:
+ * Indicate that the parent of Ressettable @obj change from @oldp to @newp.
+ * All 3 objects must implements resettable interface. @oldp or @newp may be
+ * NULL.
+ *
+ * This function will adapt the reset state of @obj so that it is coherent
+ * with the reset state of @newp. It may trigger @resettable_assert_reset()
+ * or @resettable_release_reset(). It will do such things only if the reset
+ * state of @newp and @oldp are different.
+ *
+ * When using this function during reset, it must only be called during
+ * an hold phase method. Calling this during enter or exit phase is an error.
+ */
+void resettable_change_parent(Object *obj, Object *newp, Object *oldp);
+
 /**
  * resettable_class_set_parent_phases:
  *
-- 
2.23.0