[v7,05/11] hw/core/resettable: add support for changing parent

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 avoids any glitch if both old and new parent are
already in reset.

Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/hw/resettable.h | 16 +++++++++++
 hw/core/resettable.c    | 62 +++++++++++++++++++++++++++++++++++++++--
 hw/core/trace-events    |  1 +
 3 files changed, 77 insertions(+), 2 deletions(-)

On 1/15/20 1:36 PM, Damien Hedde wrote:
> 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 avoids any glitch if both old and new parent are
> already in reset.
> 
> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   include/hw/resettable.h | 16 +++++++++++
>   hw/core/resettable.c    | 62 +++++++++++++++++++++++++++++++++++++++--
>   hw/core/trace-events    |  1 +
>   3 files changed, 77 insertions(+), 2 deletions(-)
> 
> diff --git a/include/hw/resettable.h b/include/hw/resettable.h
> index 58b3df4c22..3c87ab86c7 100644
> --- a/include/hw/resettable.h
> +++ b/include/hw/resettable.h
> @@ -194,6 +194,22 @@ 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 is changing from @oldp to @newp.
> + * All 3 objects must implement 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
> + * a 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:
>    *
> diff --git a/hw/core/resettable.c b/hw/core/resettable.c
> index 9133208487..e99bb30058 100644
> --- a/hw/core/resettable.c
> +++ b/hw/core/resettable.c
> @@ -28,12 +28,16 @@ static void resettable_phase_exit(Object *obj, void *opaque, ResetType type);
>    * enter_phase_in_progress:
>    * True if we are currently in reset enter phase.
>    *
> - * Note: This flag is only used to guarantee (using asserts) that the reset
> - * API is used correctly. We can use a global variable because we rely on the
> + * exit_phase_in_progress:
> + * count the number of exit phase we are in.
> + *
> + * Note: These flags are only used to guarantee (using asserts) that the reset
> + * API is used correctly. We can use global variables because we rely on the
>    * iothread mutex to ensure only one reset operation is in a progress at a
>    * given time.
>    */
>   static bool enter_phase_in_progress;
> +static unsigned exit_phase_in_progress;
>   
>   void resettable_reset(Object *obj, ResetType type)
>   {
> @@ -65,7 +69,9 @@ void resettable_release_reset(Object *obj, ResetType type)
>       trace_resettable_reset_release_begin(obj, type);
>       assert(!enter_phase_in_progress);
>   
> +    exit_phase_in_progress += 1;
>       resettable_phase_exit(obj, NULL, type);
> +    exit_phase_in_progress -= 1;
>   
>       trace_resettable_reset_release_end(obj);
>   }
> @@ -206,6 +212,58 @@ 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)

In patch #3 I suggested to use 'unsigned' instead (and add the new 
ResettableState::count field here with the rest of this current patch).

Using 'unsigned' imply trivial format string update in trace events, so 
regardless:

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> +{
> +    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);
> +
> +    /*
> +     * Ensure we do not change parent when in enter or exit phase.
> +     * During these phases, the reset subtree being updated is partly in reset
> +     * and partly not in reset (it depends on the actual position in
> +     * resettable_child_foreach()s). We are not able to tell in which part is a
> +     * leaving or arriving device. Thus we cannot set the reset count of the
> +     * moving device to the proper value.
> +     */
> +    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' loops will be executed below
> +     * in order to cope with the difference between the two counts.
> +     */
> +    /* 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 a2e43f1120..80e6325ab0 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
>