hw/core: add Resettable support to BusClass and DeviceClass

This commit adds support of Resettable interface to buses and devices:
+ ResettableState structure is added in the Bus/Device state
+ Resettable methods are implemented.
+ device/bus_is_in_reset function defined

This commit allows to transition the objects to the new
multi-phase interface without changing the reset behavior at all.
Object single reset method can be split into the 3 different phases
but the 3 phases are still executed in a row for a given object.
From the qdev/qbus reset api point of view, nothing is changed.
qdev_reset_all() and qbus_reset_all() are not modified as well as
device_legacy_reset().

Transition of an object must be done from parent class to child class.
Care has been taken to allow the transition of a parent class
without requiring the child classes to be transitioned at the same
time. Note that SysBus and SysBusDevice class do not need any transition
because they do not override the legacy reset method.

Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20200123132823.1117486-5-damien.hedde@greensocs.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 97 insertions, 0 deletions

diff --git a/hw/core/bus.c b/hw/core/bus.c
index 7f3d2a3dbd..2698f715bd 100644
--- a/hw/core/bus.c
+++ b/hw/core/bus.c
@@ -68,6 +68,28 @@ int qbus_walk_children(BusState *bus,
     return 0;
 }
 
+bool bus_is_in_reset(BusState *bus)
+{
+    return resettable_is_in_reset(OBJECT(bus));
+}
+
+static ResettableState *bus_get_reset_state(Object *obj)
+{
+    BusState *bus = BUS(obj);
+    return &bus->reset;
+}
+
+static void bus_reset_child_foreach(Object *obj, ResettableChildCallback cb,
+                                    void *opaque, ResetType type)
+{
+    BusState *bus = BUS(obj);
+    BusChild *kid;
+
+    QTAILQ_FOREACH(kid, &bus->children, sibling) {
+        cb(OBJECT(kid->child), opaque, type);
+    }
+}
+
 static void qbus_realize(BusState *bus, DeviceState *parent, const char *name)
 {
     const char *typename = object_get_typename(OBJECT(bus));
@@ -199,12 +221,83 @@ static char *default_bus_get_fw_dev_path(DeviceState *dev)
     return g_strdup(object_get_typename(OBJECT(dev)));
 }
 
+/**
+ * bus_phases_reset:
+ * Transition reset method for buses to allow moving
+ * smoothly from legacy reset method to multi-phases
+ */
+static void bus_phases_reset(BusState *bus)
+{
+    ResettableClass *rc = RESETTABLE_GET_CLASS(bus);
+
+    if (rc->phases.enter) {
+        rc->phases.enter(OBJECT(bus), RESET_TYPE_COLD);
+    }
+    if (rc->phases.hold) {
+        rc->phases.hold(OBJECT(bus));
+    }
+    if (rc->phases.exit) {
+        rc->phases.exit(OBJECT(bus));
+    }
+}
+
+static void bus_transitional_reset(Object *obj)
+{
+    BusClass *bc = BUS_GET_CLASS(obj);
+
+    /*
+     * This will call either @bus_phases_reset (for multi-phases transitioned
+     * buses) or a bus's specific method for not-yet transitioned buses.
+     * In both case, it does not reset children.
+     */
+    if (bc->reset) {
+        bc->reset(BUS(obj));
+    }
+}
+
+/**
+ * bus_get_transitional_reset:
+ * check if the bus's class is ready for multi-phase
+ */
+static ResettableTrFunction bus_get_transitional_reset(Object *obj)
+{
+    BusClass *dc = BUS_GET_CLASS(obj);
+    if (dc->reset != bus_phases_reset) {
+        /*
+         * dc->reset has been overridden by a subclass,
+         * the bus is not ready for multi phase yet.
+         */
+        return bus_transitional_reset;
+    }
+    return NULL;
+}
+
 static void bus_class_init(ObjectClass *class, void *data)
 {
     BusClass *bc = BUS_CLASS(class);
+    ResettableClass *rc = RESETTABLE_CLASS(class);
 
     class->unparent = bus_unparent;
     bc->get_fw_dev_path = default_bus_get_fw_dev_path;
+
+    rc->get_state = bus_get_reset_state;
+    rc->child_foreach = bus_reset_child_foreach;
+
+    /*
+     * @bus_phases_reset is put as the default reset method below, allowing
+     * to do the multi-phase transition from base classes to leaf classes. It
+     * allows a legacy-reset Bus class to extend a multi-phases-reset
+     * Bus class for the following reason:
+     * + If a base class B has been moved to multi-phase, then it does not
+     *   override this default reset method and may have defined phase methods.
+     * + A child class C (extending class B) which uses
+     *   bus_class_set_parent_reset() (or similar means) to override the
+     *   reset method will still work as expected. @bus_phases_reset function
+     *   will be registered as the parent reset method and effectively call
+     *   parent reset phases.
+     */
+    bc->reset = bus_phases_reset;
+    rc->get_transitional_function = bus_get_transitional_reset;
 }
 
 static void qbus_finalize(Object *obj)
@@ -223,6 +316,10 @@ static const TypeInfo bus_info = {
     .instance_init = qbus_initfn,
     .instance_finalize = qbus_finalize,
     .class_init = bus_class_init,
+    .interfaces = (InterfaceInfo[]) {
+        { TYPE_RESETTABLE_INTERFACE },
+        { }
+    },
 };
 
 static void bus_register_types(void)