Re: clk: clk_register is deprecated

[Stephen Boyd <sboyd@kernel.org>]

Quoting Jerome Brunet (2020-04-30 05:24:41)
> Hi Stephen,
> 
> We have a question regarding drivers which register clocks in CCF and
> later need to use these clocks.
> 
> So far, these drivers had been using clk_register() to get a 'struct
> clk*' they could later use with the linux/clk.h API.
> 
> Now that this clk_register() is deprecated in favor of
> clk_hw_register(), how are these driver supposed to get the per-user
> "struct clk*" they need ?
> 
> In this mmc thread [0] Martin proposed to go through a provider. I think
> it is overkill, especially for a device which will not provide its clocks
> to any other device.
> 
> They other way available is "hw->clk". I suspect it is not recommended
> to do so, is it ?
> 
> If not, what would be the recommended way to get the "struct clk*" from
> a newly registered "struct clk_hw *" ? Should we add something new to
> clk-provider.h API ?
> 

Yes we should add a clk_hw_get_clk() API that takes a device pointer and
a string name, mirroring the clk_get() API but cutting out the part
where we have to go through the provider to find it.

This is so that one day in "the future" we can remove hw->clk and make
that an internal detail that struct clk_hw can't see because we go
through the clk_hw::clk_core pointer instead.