Re: clk_set_parent() by name ?

[Jared McNeill <jmcneill%invisible.ca@localhost>]

On Mon, 19 Mar 2018, Manuel Bouyer wrote:

> On Mon, Mar 19, 2018 at 05:20:45PM -0300, Jared McNeill wrote:
> > I see what you mean now. The issue I have with clk_set_parent_byname is that
> > it pushes internals of the clk provider into device drivers. The names are
> > arbitrary and not consistent across ccu drivers, only really meant for
> > printing/debugging etc.
>
> Yes I understant that.
> On the other hand, the clock hierarchy knowledge in the display's driver
> is also quise soc-specific.

There are 5 different families of SoCs that share this DE implementation 
(sun4i, sun5i, sun6i, sun7i, sun9i). I don't really want to have SoC 
specific clock code in there..

> > If you're using static clock parents, you can just initialize them in your
> > ccu driver's attach function.
> >
> > If you need to dynamically adjust clock parents, do you have enough context
> > in the ccu driver on a clk_set_rate call to auto-select the correct parent?
>
> unfortunably no, not in all case.
> In allwinner/, the debe clocks are hardcoded to use pll5 as parent,
> we could probably do the same in sunxi.

Yeah I think that's reasonable.

> the video0/video1 clocks depends on the video mode, they will have to be setup
> either in the hdmi when we're using hdmi (this is where we know the video
> mode), or directly in the tcon when using the LCD outputs.
> But when using tcon without hdmi we have to reference to the video0/video1
> clocks in the device tree.

In Linux the TCON uses the two declared clocks (tcon-ch0 and tcon-ch1), 
and the clk framework automatically reparents. I think we can do the same 
without breaking abstractions here.

Cheers,
Jared