[PATCH V3 2/3] clk: Fixup errorhandling for clk_set_parent

[Rajagopal Venkat]

On 27 March 2013 15:20, Ulf Hansson <ulf.hansson at stericsson.com> wrote:
> From: Ulf Hansson <ulf.hansson at linaro.org>
>
> Fixup the broken feature of allowing reparent of a clk to the
> orhpan list and vice verse. When operating on a single-parent
> clk, the .set_parent callback for the clk hw is optional to
> implement, but for a multi-parent clk it is mandatory.
>
> Moreover improve the errorhandling by verifying the prerequisites
> before triggering clk notifiers. This will prevent unnecessary
> rollback with ABORT_RATE_CHANGE.
>
> Signed-off-by: Ulf Hansson <ulf.hansson at linaro.org>
> Cc: Rajagopal Venkat <rajagopal.venkat at linaro.org>
> ---
>  drivers/clk/clk.c |   56 ++++++++++++++++++++++++++++++++++-------------------
>  1 file changed, 36 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 97d681b..6fa301b 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -1269,15 +1269,10 @@ void __clk_reparent(struct clk *clk, struct clk *new_parent)
>         __clk_recalc_rates(clk, POST_RATE_CHANGE);
>  }
>
> -static int __clk_set_parent(struct clk *clk, struct clk *parent)
> +static u8 clk_fetch_parent_index(struct clk *clk, struct clk *parent)
>  {
> -       struct clk *old_parent;
> -       unsigned long flags;
> -       int ret = -EINVAL;
>         u8 i;
>
> -       old_parent = clk->parent;
> -
>         if (!clk->parents)
>                 clk->parents = kzalloc((sizeof(struct clk*) * clk->num_parents),
>                                                                 GFP_KERNEL);
> @@ -1297,11 +1292,14 @@ static int __clk_set_parent(struct clk *clk, struct clk *parent)
>                 }
>         }
>
> -       if (i == clk->num_parents) {
> -               pr_debug("%s: clock %s is not a possible parent of clock %s\n",
> -                               __func__, parent->name, clk->name);
> -               goto out;
> -       }
> +       return i;
> +}
> +
> +static int __clk_set_parent(struct clk *clk, struct clk *parent, u8 p_index)
> +{
> +       unsigned long flags;
> +       int ret = 0;
> +       struct clk *old_parent = clk->parent;
>
>         /* migrate prepare and enable */
>         if (clk->prepare_count)
> @@ -1314,7 +1312,8 @@ static int __clk_set_parent(struct clk *clk, struct clk *parent)
>         spin_unlock_irqrestore(&enable_lock, flags);
>
>         /* change clock input source */
> -       ret = clk->ops->set_parent(clk->hw, i);
> +       if (parent && clk->ops->set_parent)
> +               ret = clk->ops->set_parent(clk->hw, p_index);

What if clk->ops->set_parent() fails? should this clk undefined state
be handled?

>
>         /* clean up old prepare and enable */
>         spin_lock_irqsave(&enable_lock, flags);
> @@ -1325,7 +1324,6 @@ static int __clk_set_parent(struct clk *clk, struct clk *parent)
>         if (clk->prepare_count)
>                 __clk_unprepare(old_parent);
>
> -out:
>         return ret;
>  }
>
> @@ -1344,11 +1342,14 @@ out:
>  int clk_set_parent(struct clk *clk, struct clk *parent)
>  {
>         int ret = 0;
> +       u8 p_index = 0;
> +       unsigned long p_rate = 0;
>
>         if (!clk || !clk->ops)
>                 return -EINVAL;
>
> -       if (!clk->ops->set_parent)
> +       /* verify ops for for multi-parent clks */
> +       if ((clk->num_parents > 1) && (!clk->ops->set_parent))
>                 return -ENOSYS;

Should this check be moved to clk registration path? clk ops
validation is done in __clk_init().

>
>         /* prevent racing with updates to the clock topology */
> @@ -1357,19 +1358,34 @@ int clk_set_parent(struct clk *clk, struct clk *parent)
>         if (clk->parent == parent)
>                 goto out;
>
> +       /* check that we are allowed to re-parent if the clock is in use */
> +       if ((clk->flags & CLK_SET_PARENT_GATE) && clk->prepare_count) {
> +               ret = -EBUSY;
> +               goto out;
> +       }
> +
> +       /* try finding the new parent index */
> +       if (parent) {
> +               p_index = clk_fetch_parent_index(clk, parent);
> +               p_rate = parent->rate;
> +               if (p_index == clk->num_parents) {
> +                       pr_debug("%s: clk %s can not be parent of clk %s\n",
> +                                       __func__, parent->name, clk->name);
> +                       ret = -EINVAL;
> +                       goto out;
> +               }
> +       }
> +
>         /* propagate PRE_RATE_CHANGE notifications */
>         if (clk->notifier_count)
> -               ret = __clk_speculate_rates(clk, parent->rate);
> +               ret = __clk_speculate_rates(clk, p_rate);
>
>         /* abort if a driver objects */
>         if (ret == NOTIFY_STOP)
>                 goto out;
>
> -       /* only re-parent if the clock is not in use */
> -       if ((clk->flags & CLK_SET_PARENT_GATE) && clk->prepare_count)
> -               ret = -EBUSY;
> -       else
> -               ret = __clk_set_parent(clk, parent);
> +       /* do the re-parent */
> +       ret = __clk_set_parent(clk, parent, p_index);
>
>         /* propagate ABORT_RATE_CHANGE if .set_parent failed */
>         if (ret) {
> --
> 1.7.10
>
In addition, this fix is required to allow reparenting of clk to orphan list.

---
 drivers/clk/clk.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index fb5d08a..ec436e0 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1221,7 +1221,7 @@ void __clk_reparent(struct clk *clk, struct clk
*new_parent)
        struct dentry *new_parent_d;
 #endif

-       if (!clk || !new_parent)
+       if (!clk)
                return;

        hlist_del(&clk->child_node);
-- 
1.7.10.4


-- 
Regards,
Rajagopal