Messages in this thread | | | Date | Wed, 15 Dec 2021 18:54:41 +0100 | From | Pavel Machek <> | Subject | Re: [PATCH 4.19 29/74] clk: qcom: regmap-mux: fix parent clock lookup |
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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.
Yeah, I guess it happens to work.
> 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.
Well ~0 would be sensible in this case. And a comment with explanation.
> 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.
Yep, I believe that should happen, long-term.
Best regards, Pavel -- DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany [unhandled content-type:application/pgp-signature] | |