[PATCH v8 11/13] clk: qcom: gdsc: Use PM clocks to control gdsc clocks

Rajendra Nayak rnayak at codeaurora.org
Fri Nov 27 00:29:40 PST 2015

Hi Stephen,

>> +static int gdsc_attach(struct generic_pm_domain *domain, struct device
>> *dev)
>> +{
>> +	int ret, i = 0, j = 0;
>> +	struct gdsc *sc = domain_to_gdsc(domain);
>> +	struct of_phandle_args clkspec;
>> +	struct device_node *np = dev->of_node;
>> +
>> +	if (!sc->clock_count)
>> +		return 0;
>> +
>> +	ret = pm_clk_create(dev);
>> +	if (ret) {
>> +		dev_dbg(dev, "pm_clk_create failed %d\n", ret);
>> +		return ret;
>> +	}
>> +
>> +	sc->clks = devm_kcalloc(dev, sc->clock_count, sizeof(sc->clks),
>> +				       GFP_KERNEL);
>> +	if (!sc->clks)
>> +		return -ENOMEM;
>> +
>> +	while (!of_parse_phandle_with_args(np, "clocks", "#clock-cells", i,
>> +					   &clkspec)) {
>> +		if (match(clkspec.args[0], sc->clocks, sc->clock_count)) {
> I'm lost. I was hoping we could just make up a clkspec on the
> stack and pass it over to of_clk_get_from_provider() without
> having to go through the np of the client device. The point being
> to avoid forcing this code from knowing about the consumer
> binding or connection name choice for each device. Instead, it
> assumes that it's a #clock-cells=<1> binding and gets the clocks
> by passing the 1 cell data without calling
> of_parse_phandle_with_args().
> Now, one downside of that approach is that it's DT centric (also
> of_clk_get_from_provider() is not an exported symbol yet). So I'm
> really starting to lean towards exposing __clk_create_clk() (or
> some better named "provider" function) that will allow clk
> providers to turn their clk_hw structure into a struct clk
> pointer. That avoids the DT centric design, and avoids binding
> the provider to the connection ids too.

Stephen, I started to relook at these patches, avoiding the DT centric
design and implementing a clk helper API as you suggested above.

While this would work for GDSCs with just one device, its hard to scale
if we ever run into GDSCs with multiple devices (In which case you
need to know which device within the GDSC needs which clocks)

Do you think its a fair limitation (one device per gdsc) to live with?
because I can't seem to figure how a non DT centric design would otherwise


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