Re: [Qemu-devel] [PATCH V1 03/10] qemu-clk: allow to bind two clocks together

[Peter Maydell]

On 5 October 2016 at 23:10,  <address@hidden> wrote:
> From: KONRAD Frederic <address@hidden>
>
> This introduces the clock binding and the update part.
> When the qemu_clk_rate_update(qemu_clk, int) function is called:
>   * The clock callback is called on the qemu_clk so it can change the rate.
>   * The qemu_clk_rate_update function is called on all the driven clock.
>
> Signed-off-by: KONRAD Frederic <address@hidden>
> ---
>  include/qemu/qemu-clock.h | 66 
> +++++++++++++++++++++++++++++++++++++++++++++++
>  qemu-clock.c              | 56 ++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 122 insertions(+)
>
> diff --git a/include/qemu/qemu-clock.h b/include/qemu/qemu-clock.h
> index 1d56a2e..d575566 100644
> --- a/include/qemu/qemu-clock.h
> +++ b/include/qemu/qemu-clock.h
> @@ -27,15 +27,29 @@
>  #include "qemu/osdep.h"
>  #include "qom/object.h"
>
> +typedef uint64_t (*qemu_clk_on_rate_update_cb)(void *opaque, uint64_t rate);

I think it's more readable to have the typedef define
the function type, not the pointer-to-function type. (See for
instance CPReadFn, CPWriteFn in target-arm/cpu.h.) That way
your function pointers in structs and so on have type
"MyFnType *fn;" and are more obviously pointers.

(Also QEMU style says camelcase for types. QEMUClkRateUpdateCallback?)

> +
>  #define TYPE_CLOCK "qemu-clk"
>  #define QEMU_CLOCK(obj) OBJECT_CHECK(struct qemu_clk, (obj), TYPE_CLOCK)
>
> +typedef struct ClkList ClkList;
> +
>  typedef struct qemu_clk {
>      /*< private >*/
>      Object parent_obj;
>      char *name;            /* name of this clock in the device. */
> +    uint64_t in_rate;      /* rate of the clock which drive this pin. */
> +    uint64_t out_rate;     /* rate of this clock pin. */
> +    void *opaque;
> +    qemu_clk_on_rate_update_cb cb;
> +    QLIST_HEAD(, ClkList) bound;
>  } *qemu_clk;
>
> +struct ClkList {
> +    qemu_clk clk;
> +    QLIST_ENTRY(ClkList) node;
> +};
> +
>  /**
>   * qemu_clk_attach_to_device:
>   * @dev: the device on which the clock need to be attached.
> @@ -59,4 +73,56 @@ void qemu_clk_attach_to_device(DeviceState *dev, qemu_clk 
> clk,
>   */
>  qemu_clk qemu_clk_get_pin(DeviceState *dev, const char *name);
>
> +/**
> + * qemu_clk_bind_clock:
> + * @out: the clock output.
> + * @in: the clock input.
> + *
> + * Connect the clock together. This is unidirectional so a
> + * qemu_clk_update_rate will go from @out to @in.
> + *
> + */
> +void qemu_clk_bind_clock(qemu_clk out, qemu_clk in);

Hang on, I thought that passing a clock to
qemu_clk_attach_to_device() was going to be the thing
that connected the clock up...

> +
> +/**
> + * qemu_clk_unbound:
> + * @out: the clock output.
> + * @in: the clock input.
> + *
> + * Disconnect the clocks if they were bound together.
> + *
> + */
> +void qemu_clk_unbind(qemu_clk out, qemu_clk in);

Function prototype and comment don't match...

> +
> +/**
> + * qemu_clk_update_rate:
> + * @clk: the clock to update.
> + * @rate: the new rate.
> + *
> + * Update the @clk to the new @rate.
> + *
> + */
> +void qemu_clk_update_rate(qemu_clk clk, uint64_t rate);

What units is this 'rate' in ?

> +
> +/**
> + * qemu_clk_refresh:
> + * @clk: the clock to be refreshed.
> + *
> + * If a model alters the topology of a clock tree, it must call this function
> + * to refresh the clock tree.
> + *
> + */
> +void qemu_clk_refresh(qemu_clk clk);

...for which clock in the tree does it have to call the function?
All of them? Any one of them at random?

> +
> +/**
> + * qemu_clk_set_callback:
> + * @clk: the clock where to set the callback.
> + * @cb: the callback to associate to the callback.
> + * @opaque: the opaque data passed to the calback.
> + *
> + */
> +void qemu_clk_set_callback(qemu_clk clk,
> +                           qemu_clk_on_rate_update_cb cb,
> +                           void *opaque);
> +
>  #endif /* QEMU_CLOCK_H */
> diff --git a/qemu-clock.c b/qemu-clock.c
> index 0ba6caf..541f615 100644
> --- a/qemu-clock.c
> +++ b/qemu-clock.c
> @@ -37,6 +37,62 @@
>      }                                                                        
> \
>  } while (0);
>
> +void qemu_clk_refresh(qemu_clk clk)
> +{
> +    qemu_clk_update_rate(clk, clk->in_rate);
> +}
> +
> +void qemu_clk_update_rate(qemu_clk clk, uint64_t rate)
> +{
> +    ClkList *child;
> +
> +    clk->in_rate = rate;
> +    clk->out_rate = rate;
> +
> +    if (clk->cb) {
> +        clk->out_rate = clk->cb(clk->opaque, rate);
> +    }
> +
> +    DPRINTF("%s output rate updated to %" PRIu64 "\n",
> +            object_get_canonical_path(OBJECT(clk)),
> +            clk->out_rate);
> +
> +    QLIST_FOREACH(child, &clk->bound, node) {
> +        qemu_clk_update_rate(child->clk, clk->out_rate);
> +    }
> +}
> +
> +void qemu_clk_bind_clock(qemu_clk out, qemu_clk in)
> +{
> +    ClkList *child;
> +
> +    child = g_malloc(sizeof(child));
> +    assert(child);
> +    child->clk = in;
> +    QLIST_INSERT_HEAD(&out->bound, child, node);
> +    qemu_clk_update_rate(in, out->out_rate);
> +}
> +
> +void qemu_clk_unbind(qemu_clk out, qemu_clk in)
> +{
> +    ClkList *child, *next;
> +
> +    QLIST_FOREACH_SAFE(child, &out->bound, node, next) {
> +        if (child->clk == in) {
> +            QLIST_REMOVE(child, node);
> +            g_free(child);
> +        }
> +    }
> +}
> +
> +void qemu_clk_set_callback(qemu_clk clk,
> +                           qemu_clk_on_rate_update_cb cb,
> +                           void *opaque)
> +{
> +    clk->cb = cb;
> +    clk->opaque = opaque;
> +}
> +
>  void qemu_clk_attach_to_device(DeviceState *dev, qemu_clk clk,
>                                 const char *name)
>  {
> --
> 2.5.5
>


thanks
-- PMM