Re: [PATCH 2/3] clk: let of_clk_get_parent_name() fail for invalid clock-indices

Masahiro Yamada
2015-11-22T06:03:50Z

Hi Stephen,

2015-11-21 2:45 GMT+09:00 Stephen Boyd <sboyd@codeaurora.org>:
> On 11/20, Masahiro Yamada wrote:
>> Currently, of_clk_get_parent_name() returns a wrong parent clock name
>> when "clock-indices" property exists and the given index is not found
>> in the property. In this case, NULL should be returned.
>>
>> For example,
>>
>> oscillator {
>> compatible = "myclocktype";
>> #clock-cells = <1>;
>> clock-indices = <1>, <3>;
>> clock-output-names = "clka", "clkb";
>> };
>>
>> Currently, of_clk_get_parent_name(np, 0) returns "clka", but should
>> return NULL because "clock-indices" does not contain <0>.
>
> What is np pointing at? Something like:
>
> consumer {
> clocks = <&oscillator 0>;
> };
>
> Which would be invalid DT because oscillator doesn't have an
> output for index 0?

You are right. My example was confusing.

oscillator: oscillator {
compatible = "myclocktype";
#clock-cells = <1>;
clock-indices = <1>, <3>;
clock-output-names = "clka", "clkb";
};

consumer {
compatible = "myclockconsumer";
clocks = <&oscillator 0>;
};

Currently, of_clk_get_parent_name(consumer_np, 0) returns "clks", but
should return NULL;

I will rephrase the git-log in v2.

>>
>> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
>> @@ -3068,17 +3065,20 @@ const char *of_clk_get_parent_name(struct device_node *np, int index)
>> return NULL;
>>
>> index = clkspec.args_count ? clkspec.args[0] : 0;
>> - count = 0;
>>
>> /* if there is an indices property, use it to transfer the index
>> * specified into an array offset for the clock-output-names property.
>> */
>> - of_property_for_each_u32(clkspec.np, "clock-indices", prop, vp, pv) {
>> - if (index == pv) {
>> - index = count;
>> - break;
>> - }
>> - count++;
>> + list = of_get_property(clkspec.np, "clock-indices", &len);
>> + if (list) {
>> + len /= sizeof(*list);
>> + for (i = 0; i < len; i++)
>> + if (index == be32_to_cpup(list++)) {
>> + index = i;
>> + break;
>> + }
>> + if (i == len)
>> + return NULL;
>> }
>
> Why can't we leave everything in place and check count == len at
> the end? i.e.
>
> of_property_for_each_u32(clkspec.np, "clock-indices", prop, vp, pv) {
> if (index == pv) {
> index = count;
> break;
> }
> count++;
> }
>
> if (count == of_property_count_u32_elems(clkspec.np, "clock-indices"))
> return NULL
>

Of course we can, although we have to mention "clock-indices" twice.

A good thing for of_get_property() is that we can get both the value
and the length
at the same time.

--
Best Regards
Masahiro Yamada