[PATCH v6 5/5] clk: Implement clk_unregister

Sylwester Nawrocki
2013-09-04T15:43:19Z

On 08/30/2013 04:53 PM, Sylwester Nawrocki wrote:
> clk_unregister() is currently not implemented and it is required when
> a clock provider module needs to be unloaded.
>
> Normally the clock supplier module is prevented to be unloaded by
> taking reference on the module in clk_get().
>
> For cases when the clock supplier module deinitializes despite the
> consumers of its clocks holding a reference on the module, e.g. when
> the driver is unbound through "unbind" sysfs attribute, there are
> empty clock ops added. These ops are assigned temporarily to struct
> clk and used until all consumers release the clock, to avoid invoking
> callbacks from the module which just got removed.
>
> Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
> Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
> ---
[...]
> /**
> * clk_unregister - unregister a currently registered clock
> * @clk: clock to unregister
> - *
> - * Currently unimplemented.
> */
> -void clk_unregister(struct clk *clk) {}
> +void clk_unregister(struct clk *clk)
> +{
> + unsigned long flags;
> +
> + clk_prepare_lock();
> +
> + if (!clk || IS_ERR(clk)) {
> + pr_err("%s: invalid clock: %p\n", __func__, clk);
> + goto out;
> + }

Actually this check could be done before taking the mutex. And to handle
NULL clocks properly it should be something like:

if (!clk || WARN_ON_ONCE(IS_ERR(clk)))
return;

I will hold on with posting a corrected version until there are any
further comments.

> + if (clk->ops == &clk_nodrv_ops) {
> + pr_err("%s: unregistered clock: %s\n", __func__, clk->name);
> + goto out;
> + }
> + /*
> + * Assign empty clock ops for consumers that might still hold
> + * a reference to this clock.
> + */
> + flags = clk_enable_lock();
> + clk->ops = &clk_nodrv_ops;
> + clk_enable_unlock(flags);
> +
> + if (!hlist_empty(&clk->children)) {
> + struct clk *child;
> +
> + /* Reparent all children to the orphan list. */
> + hlist_for_each_entry(child, &clk->children, child_node)
> + clk_set_parent(child, NULL);
> + }
> +
> + clk_debug_unregister(clk);
> +
> + hlist_del_init(&clk->child_node);
> +
> + if (clk->prepare_count)
> + pr_warn("%s: unregistering prepared clock: %s\n",
> + __func__, clk->name);
> +
> + kref_put(&clk->ref, __clk_release);
> +out:
> + clk_prepare_unlock();
> +}
> EXPORT_SYMBOL_GPL(clk_unregister);