On 15/12/2021 12:16, Pavel Machek wrote:
Hi!
The function mux_get_parent() uses qcom_find_src_index() to find the
parent clock index, which is incorrect: qcom_find_src_index() uses src
enum for the lookup, while mux_get_parent() should use cfg field (which
corresponds to the register value). Add qcom_find_cfg_index() function
doing this kind of lookup and use it for mux parent lookup.
This appears to have problems with error handling.
+++ b/drivers/clk/qcom/clk-regmap-mux.c
@@ -36,7 +36,7 @@ static u8 mux_get_parent(struct clk_hw *
val &= mask;
if (mux->parent_map)
- return qcom_find_src_index(hw, mux->parent_map, val);
+ return qcom_find_cfg_index(hw, mux->parent_map, val);
return val;
}
So this returns u8.
+int qcom_find_cfg_index(struct clk_hw *hw, const struct parent_map *map, u8 cfg)
+{
+ int i, num_parents = clk_hw_get_num_parents(hw);
+
+ for (i = 0; i < num_parents; i++)
+ if (cfg == map[i].cfg)
+ return i;
+
+ return -ENOENT;
+}
In case of error, -ENOENT will be cast to u8 in caller. I don't
believe that is correct.
Unfortunately there is no way to return proper error code from
clk_ops->get_parent() callback. However returning -ENOENT would
translate to 254. Then clk_core_get_parent_by_index() would determine
that there is no such parent and return NULL. A call to clk_set_parent
would reparent the clock.
Returning some sensible default (e.g. 0) would be much worse, since then
the clock subsystem would assume that the clock has correct parent. A
call to clk_set_parent would always result in ops->set_parent() call,
reparenting the clock correctly.
Most probably it would be correct to make ops->get_parent() return int
instead of u8 (either an index or an -ERROR). However this was out of
scope for this patch.
--
With best wishes
Dmitry
