Add clk_list_freq() methods

[br]

Summary

Add clk_list_freq() methods

This is needed for the interface between cpufreq and SCMI.

In the SCMI scenario available CPU frequencies are not described in the DTS file, we have to get them by querying SCMI.

Test Plan

Tested on ARM Morello platform

[mmel]

I don't think this feature is appropriate for a generic layer. Practically no physical clock can implement it. A PLL can typically produce trillions of discrete frequencies, which makes it practically impossible to enumerate.

IMHO you should add it to scmi_clknode_methods as a custom function (with an appropriate prefix ) Simply create an .m file for the method definition and add this new method to the method table.

[br]

In D37325#849561, @mmel wrote:

I don't think this feature is appropriate for a generic layer. Practically no physical clock can implement it. A PLL can typically produce trillions of discrete frequencies, which makes it practically impossible to enumerate.

IMHO you should add it to scmi_clknode_methods as a custom function (with an appropriate prefix ) Simply create an .m file for the method definition and add this new method to the method table.

Does it mean I don't need to alter extres/clk at all?
structs clk and clknode are defined in clk.c so I can't really use it outside generic layer.
So I will still need some wrappers similar to currently proposed clk_list_freq() or clknode_list_freq() that could dereference clk_t *