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

[Peter Maydell <peter.maydell@linaro.org>]

On Fri, 18 Oct 2019 at 16:07, Damien Hedde <damien.hedde@greensocs.com> 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 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;

This is another global that I don't think we should have.
Is it also just for asserts ?


> +
>  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

"loops"

> +     * in order to cope with the diff between the two count.

"difference". "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 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.

"is changing from"

> + * All 3 objects must implements resettable interface. @oldp or @newp may be

"implement"

> + * 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.

"a hold phase"

> + */
> +void resettable_change_parent(Object *obj, Object *newp, Object *oldp);
> +

thanks
-- PMM