Re: of_clk_add_(hw_)providers multipule times for one node?

Stephen Boyd
2016-08-04T21:25:56Z

+Rob in case he has any insight

On 07/09, Masahiro Yamada wrote:
> Hi.
>
> I think the current code allows to add
> clk_providers multiple times against one DT node.
>
> Are there cases that really need to do so?

If we have clk drivers that have a device driver structure and
also use CLK_OF_DECLARE then we could get into a situation where
they register two providers for the same device node. I can't
think of any other situation where this would happen though.

>
>
> I am thinking the behavior of __of_clk_get_from_provider() is strange.
>
>
> The result of __of_clk_get_from_provider() has three patterns:
>
> [1] success
> [2] return -EPROBE_DEFER
> [3] return -EINVAL (if clkspec == NULL)
>
>
> [3] is a rare case.
> So, almost all error cases are treated as -EPROBE_DEFER.
>

It used to return the last provider's error, but I accidentally
changed that behavior when adding clk_hw providers in commit
0861e5b8cf80 (clk: Add clk_hw OF clk providers, 2016-02-05).
Nobody seems to have complained though, so you're the first to
have reported this.

>
>
> A strange scenario
> ------------------
>
> If a too big clock index is passed in clkspec,
> of_clk_src_onecell_get() returns -EINVAL. This is reasonable.
>
>
> But, __of_clk_get_from_provider() tries to search next nodes despite
> that it has already failed to get a clk.
>
> Then, it reaches the end of list_for_each_entry() loop, and returns
> -EPROBE_DEFER. This is not deferred probe at all! In this case,
> __of_clk_get_from_provider() should return -EINVAL.
>
>
> If this is a bug, I am happy to volunteer to fix it.
>
>

Right, a behavior change that shouldn't have happened. How about
this patch?

-----8<-----
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index d584004f7af7..cd8106b17cf4 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -3125,7 +3125,7 @@ struct clk *__of_clk_get_from_provider(struct of_phandle_args *clkspec,
{
struct of_clk_provider *provider;
struct clk *clk = ERR_PTR(-EPROBE_DEFER);
- struct clk_hw *hw = ERR_PTR(-EPROBE_DEFER);
+ struct clk_hw *hw;

if (!clkspec)
return ERR_PTR(-EINVAL);
@@ -3133,12 +3133,13 @@ struct clk *__of_clk_get_from_provider(struct of_phandle_args *clkspec,
/* Check if we have such a provider in our array */
mutex_lock(&of_clk_mutex);
list_for_each_entry(provider, &of_clk_providers, link) {
- if (provider->node == clkspec->np)
+ if (provider->node == clkspec->np) {
hw = __of_clk_get_hw_from_provider(provider, clkspec);
- if (!IS_ERR(hw)) {
clk = __clk_create_clk(hw, dev_id, con_id);
+ }

- if (!IS_ERR(clk) && !__clk_get(clk)) {
+ if (!IS_ERR(clk)) {
+ if (!__clk_get(clk)) {
__clk_free_clk(clk);
clk = ERR_PTR(-ENOENT);
}

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