linux-kernel - Re: [PATCH v2 35/65] clk: ux500: sysctrl: Add a determine

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Date:   Thu, 10 Nov 2022 14:05:16 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Maxime Ripard <maxime@...no.tech>, Stephen Boyd <sboyd@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
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Subject: Re: [PATCH v2 35/65] clk: ux500: sysctrl: Add a determine_rate hook

On Thu, 10 Nov 2022 at 12:39, Linus Walleij <linus.walleij@...aro.org> wrote:
>
> On Thu, Nov 10, 2022 at 12:29 PM Ulf Hansson <ulf.hansson@...aro.org> wrote:
> > On Fri, 4 Nov 2022 at 14:32, Maxime Ripard <maxime@...no.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.

It's definitely not working, but the corresponding clocks ("ulpclk",
"intclk", "audioclk", etc) are being registered in ab8500_reg_clks().

What seems to be missing is a DT conversion for these clocks, so they
can be consumed properly. Right?

Kind regards
Uffe