Re: [PATCH v6 2/2] mmc: host: meson-mx-sdhc: new driver for the Amlogic Meson SDHC host

[Ulf Hansson]

On Tue, 5 May 2020 at 18:05, Jerome Brunet <jbrunet@xxxxxxxxxxxx> wrote:
>
>
> On Tue 05 May 2020 at 10:17, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
>
> > [...]
> >
> >> >> > +
> >> >> > +     return devm_of_clk_add_hw_provider(dev, of_clk_hw_onecell_get,
> >> >> > +                                        onecell_data);
> >> >>
> >> >> I think registering a provider for a module that does not provide clocks
> >> >> to any other device is a bit overkill.
> >> >>
> >> >> I understand the matter is getting the per-user clk* pointer.
> >> >> Since this is the module registering the clock, you can use clk_hw->clk
> >> >> to get it.
> >> >>
> >> >> Once you have the clk* of the leaf clocks, you don't even need to keep
> >> >> track of the clk_hw* since you are using devm_
> >> >>
> >> >> Afterward, we should propably discuss with Stephen if something should
> >> >> be added in CCF to get a struct clk* from struct clk_hw*.
> >> >>
> >> >
> >> > [...]
> >> >
> >> > Hmm.
> >> >
> >> > I am not sure the above is a good idea, at all. Unless, I am
> >> > misunderstanding your point, which may be the case.
> >> >
> >> > I think above "shortcuts" could lead to abuse of the clock framework
> >> > and its internal data structures. When going forward, this could make
> >> > it unnecessary harder to maintain the clock framework.
> >> >
> >> > I know, it's not my responsibility, but from my experience with MMC
> >> > and SDIO interfaces, is that those have been too easy abuse - since
> >> > most of the data structures and interfaces have been exported. Now,
> >> > it's hard to roll back that, if you see what I mean.
> >>
> >> Indeed, it worth clarifying this first.
> >>
> >> With clk_register deprecated in favor of clk_hw_register, we are likely
> >> to see that case rise elsewhere.
> >>
> >
> > So, according to the separate discussion [1], I think we can let
> > Martin decide what option to implement at this point.
> >
> > 1. Implement the "clk_hw_get_clk()" approach. The preferred option,
> > but requires wider changes of the clock subsystem as well.
> >
> > 2. Keep the existing approach, with devm_clk_get(). I am fine with
> > this as well, we can always switch to 1) later on.
>
> I have a problem with this approach.
> The dt-bindings would include "#clock-cells = <1>" for a device that
> does not actually provide and only needs it has a temporary work around.
> Those bindings are supposed to be stable ...

I agree, the bindings need to be stable.

What is the problem of keeping "#clock-cells = <1>" around, when we
move to a clk_hw_get_clk() approach in the next step?

>
> I have proposed 2 other short term solutions, let's see how it goes

Yes, seems like we need to wait for Stephen's input then.

Kind regards
Uffe