+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);
 			}

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project