On 12/09, Kuninori Morimoto wrote:
>
> Hi Stephen
>
> > > @@ -111,14 +112,13 @@ int asoc_simple_card_parse_clk(struct device_node
> > > *node,
> > > * or "system-clock-frequency = <xxx>"
> > > * or device's module clock.
> > > */
> > > - clk = of_clk_get(node, 0);
> > > + clk = devm_get_clk_from_child(dev, node, NULL);
> > > if (!IS_ERR(clk)) {
> > > simple_dai->sysclk = clk_get_rate(clk);
> > > - simple_dai->clk = clk;
> > > } else if (!of_property_read_u32(node, "system-clock-frequency", &val))
> > > {
> > > simple_dai->sysclk = val;
> > > } else {
> > > - clk = of_clk_get(dai_of_node, 0);
> > > + clk = devm_get_clk_from_child(dev, dai_of_node, NULL);
> >
> >
> > I was confused for a minute about how the second of_clk_get()
> > call with the dai_link node could work. Is that documented
> > anywhere or used by anyone? It seems like it's at least another
> > child node of the sound node (which is dev here) so it seems ok.
>
> Documentation/devicetree/bindings/sound/simple-card.txt
> explains 1st of_clk_get will be used as "if needed",
> 2nd of_clk_get will be used as "not needed pattern".
> 1st pattern will use specific clock, 2nd pattern will use
> "cpu" or "codec" clock.
> 2nd one was added by someone (I forgot), and many driver is
> based on this feature.
>
Can you point to some dts file in the kernel that falls into the
devm_get_clk_from_child(dev, dai_of_node, NULL) part?
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