Re: [PATCH v2 35/65] clk: ux500: sysctrl: Add a determine_rate hook

Linus Walleij
2022-11-10T11:40:12Z

On Thu, Nov 10, 2022 at 12:29 PM Ulf Hansson <ulf.hansson@linaro.org> wrote:
> On Fri, 4 Nov 2022 at 14:32, Maxime Ripard <maxime@cerno.tech> wrote:
> >
> > The UX500 sysctrl "set_parent" clocks implement a mux with a set_parent
> > hook, but doesn't provide a determine_rate implementation.
> >
> > This is a bit odd, since set_parent() is there to, as its name implies,
> > change the parent of a clock. However, the most likely candidate to
> > trigger that parent change is a call to clk_set_rate(), with
> > determine_rate() figuring out which parent is the best suited for a
> > given rate.
> >
> > The other trigger would be a call to clk_set_parent(), but it's far less
> > used, and it doesn't look like there's any obvious user for that clock.
>
> If I recall correctly, that is the use case we did target for these
> types of clocks. See sound/soc/ux500/ux500_ab85xx.c, for example.

Hm I am trying to get that driver to work ... from time to time.
It's just that ALSA SoC DT has changed to much that it turns out
into a complete rewrite :/

So in sound/soc/ux500/mop500_ab8500.c
I see this:

status = clk_set_parent(drvdata->clk_ptr_intclk, clk_ptr);
if (status)
(...)

and there is elaborate code to switch between "SYSCLK" and
"ULPCLK" (ulta-low power clock). Just like you say... however
a clock named SYSCLK or ULPCLK does not appear in the
code in drivers/clk/ux500 or any DT bindings so... it seems to
be non-working for the time being.

Yours,
Linus Walleij