include/hw/resettable.h

   1 /*
   2  * Resettable interface header.
   3  *
   4  * Copyright (c) 2019 GreenSocs SAS
   5  *
   6  * Authors:
   7  *   Damien Hedde
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  10  * See the COPYING file in the top-level directory.
  11  */
  12
  13 #ifndef HW_RESETTABLE_H
  14 #define HW_RESETTABLE_H
  15
  16 #include "qom/object.h"
  17
  18 #define TYPE_RESETTABLE_INTERFACE "resettable"
  19
  20 typedef struct ResettableClass ResettableClass;
  21 DECLARE_CLASS_CHECKERS(ResettableClass, RESETTABLE,
  22                        TYPE_RESETTABLE_INTERFACE)
  23
  24
  25 typedef struct ResettableState ResettableState;
  26
  27 /**
  28  * ResetType:
  29  * Types of reset.
  30  *
  31  * + Cold: reset resulting from a power cycle of the object.
  32  * + Wakeup: reset resulting from a wake-up from a suspended state.
  33  *
  34  * TODO: Support has to be added to handle more types. In particular,
  35  * ResettableState structure needs to be expanded.
  36  */
  37 typedef enum ResetType {
  38     RESET_TYPE_COLD,
  39     RESET_TYPE_SNAPSHOT_LOAD,
  40     RESET_TYPE_WAKEUP,
  41     RESET_TYPE_S390_CPU_INITIAL,
  42     RESET_TYPE_S390_CPU_NORMAL,
  43 } ResetType;
  44
  45 /*
  46  * ResettableClass:
  47  * Interface for resettable objects.
  48  *
  49  * See docs/devel/reset.rst for more detailed information about how QEMU models
  50  * reset. This whole API must only be used when holding the iothread mutex.
  51  *
  52  * All objects which can be reset must implement this interface;
  53  * it is usually provided by a base class such as DeviceClass or BusClass.
  54  * Every Resettable object must maintain some state tracking the
  55  * progress of a reset operation by providing a ResettableState structure.
  56  * The functions defined in this module take care of updating the
  57  * state of the reset.
  58  * The base class implementation of the interface provides this
  59  * state and implements the associated method: get_state.
  60  *
  61  * Concrete object implementations (typically specific devices
  62  * such as a UART model) should provide the functions
  63  * for the phases.enter, phases.hold and phases.exit methods, which
  64  * they can set in their class init function, either directly or
  65  * by calling resettable_class_set_parent_phases().
  66  * The phase methods are guaranteed to only only ever be called once
  67  * for any reset event, in the order 'enter', 'hold', 'exit'.
  68  * An object will always move quickly from 'enter' to 'hold'
  69  * but might remain in 'hold' for an arbitrary period of time
  70  * before eventually reset is deasserted and the 'exit' phase is called.
  71  * Object implementations should be prepared for functions handling
  72  * inbound connections from other devices (such as qemu_irq handler
  73  * functions) to be called at any point during reset after their
  74  * 'enter' method has been called.
  75  *
  76  * Users of a resettable object should not call these methods
  77  * directly, but instead use the function resettable_reset().
  78  *
  79  * @phases.enter: This phase is called when the object enters reset. It
  80  * should reset local state of the object, but it must not do anything that
  81  * has a side-effect on other objects, such as raising or lowering a qemu_irq
  82  * line or reading or writing guest memory. It takes the reset's type as
  83  * argument.
  84  *
  85  * @phases.hold: This phase is called for entry into reset, once every object
  86  * in the system which is being reset has had its @phases.enter method called.
  87  * At this point devices can do actions that affect other objects.
  88  *
  89  * @phases.exit: This phase is called when the object leaves the reset state.
  90  * Actions affecting other objects are permitted.
  91  *
  92  * @get_state: Mandatory method which must return a pointer to a
  93  * ResettableState.
  94  *
  95  * @child_foreach: Executes a given callback on every Resettable child. Child
  96  * in this context means a child in the qbus tree, so the children of a qbus
  97  * are the devices on it, and the children of a device are all the buses it
  98  * owns. This is not the same as the QOM object hierarchy. The function takes
  99  * additional opaque and ResetType arguments which must be passed unmodified to
 100  * the callback.
 101  */
 102 typedef void (*ResettableEnterPhase)(Object *obj, ResetType type);
 103 typedef void (*ResettableHoldPhase)(Object *obj, ResetType type);
 104 typedef void (*ResettableExitPhase)(Object *obj, ResetType type);
 105 typedef ResettableState * (*ResettableGetState)(Object *obj);
 106 typedef void (*ResettableChildCallback)(Object *, void *opaque,
 107                                         ResetType type);
 108 typedef void (*ResettableChildForeach)(Object *obj,
 109                                        ResettableChildCallback cb,
 110                                        void *opaque, ResetType type);
 111 typedef struct ResettablePhases {
 112     ResettableEnterPhase enter;
 113     ResettableHoldPhase hold;
 114     ResettableExitPhase exit;
 115 } ResettablePhases;
 116 struct ResettableClass {
 117     InterfaceClass parent_class;
 118
 119     /* Phase methods */
 120     ResettablePhases phases;
 121
 122     /* State access method */
 123     ResettableGetState get_state;
 124
 125     /* Hierarchy handling method */
 126     ResettableChildForeach child_foreach;
 127 };
 128
 129 /**
 130  * ResettableState:
 131  * Structure holding reset related state. The fields should not be accessed
 132  * directly; the definition is here to allow further inclusion into other
 133  * objects.
 134  *
 135  * @count: Number of reset level the object is into. It is incremented when
 136  * the reset operation starts and decremented when it finishes.
 137  * @hold_phase_pending: flag which indicates that we need to invoke the 'hold'
 138  * phase handler for this object.
 139  * @exit_phase_in_progress: true if we are currently in the exit phase
 140  */
 141 struct ResettableState {
 142     unsigned count;
 143     bool hold_phase_pending;
 144     bool exit_phase_in_progress;
 145 };
 146
 147 /**
 148  * resettable_state_clear:
 149  * Clear the state. It puts the state to the initial (zeroed) state required
 150  * to reuse an object. Typically used in realize step of base classes
 151  * implementing the interface.
 152  */
 153 static inline void resettable_state_clear(ResettableState *state)
 154 {
 155     memset(state, 0, sizeof(ResettableState));
 156 }
 157
 158 /**
 159  * resettable_reset:
 160  * Trigger a reset on an object @obj of type @type. @obj must implement
 161  * Resettable interface.
 162  *
 163  * Calling this function is equivalent to calling @resettable_assert_reset()
 164  * then @resettable_release_reset().
 165  */
 166 void resettable_reset(Object *obj, ResetType type);
 167
 168 /**
 169  * resettable_assert_reset:
 170  * Put an object @obj into reset. @obj must implement Resettable interface.
 171  *
 172  * @resettable_release_reset() must eventually be called after this call.
 173  * There must be one call to @resettable_release_reset() per call of
 174  * @resettable_assert_reset(), with the same type argument.
 175  *
 176  * NOTE: Until support for migration is added, the @resettable_release_reset()
 177  * must not be delayed. It must occur just after @resettable_assert_reset() so
 178  * that migration cannot be triggered in between. Prefer using
 179  * @resettable_reset() for now.
 180  */
 181 void resettable_assert_reset(Object *obj, ResetType type);
 182
 183 /**
 184  * resettable_release_reset:
 185  * Release the object @obj from reset. @obj must implement Resettable interface.
 186  *
 187  * See @resettable_assert_reset() description for details.
 188  */
 189 void resettable_release_reset(Object *obj, ResetType type);
 190
 191 /**
 192  * resettable_is_in_reset:
 193  * Return true if @obj is under reset.
 194  *
 195  * @obj must implement Resettable interface.
 196  */
 197 bool resettable_is_in_reset(Object *obj);
 198
 199 /**
 200  * resettable_change_parent:
 201  * Indicate that the parent of Ressettable @obj is changing from @oldp to @newp.
 202  * All 3 objects must implement resettable interface. @oldp or @newp may be
 203  * NULL.
 204  *
 205  * This function will adapt the reset state of @obj so that it is coherent
 206  * with the reset state of @newp. It may trigger @resettable_assert_reset()
 207  * or @resettable_release_reset(). It will do such things only if the reset
 208  * state of @newp and @oldp are different.
 209  *
 210  * When using this function during reset, it must only be called during
 211  * a hold phase method. Calling this during enter or exit phase is an error.
 212  */
 213 void resettable_change_parent(Object *obj, Object *newp, Object *oldp);
 214
 215 /**
 216  * resettable_cold_reset_fn:
 217  * Helper to call resettable_reset((Object *) opaque, RESET_TYPE_COLD).
 218  *
 219  * This function is typically useful to register a reset handler with
 220  * qemu_register_reset.
 221  */
 222 void resettable_cold_reset_fn(void *opaque);
 223
 224 /**
 225  * resettable_class_set_parent_phases:
 226  *
 227  * Save @rc current reset phases into @parent_phases and override @rc phases
 228  * by the given new methods (@enter, @hold and @exit).
 229  * Each phase is overridden only if the new one is not NULL allowing to
 230  * override a subset of phases.
 231  */
 232 void resettable_class_set_parent_phases(ResettableClass *rc,
 233                                         ResettableEnterPhase enter,
 234                                         ResettableHoldPhase hold,
 235                                         ResettableExitPhase exit,
 236                                         ResettablePhases *parent_phases);
 237
 238 #endif