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

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Date:   Fri, 11 Nov 2022 10:20:34 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Maxime Ripard <maxime@...no.tech>, Stephen Boyd <sboyd@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Chen-Yu Tsai <wens@...e.org>, Daniel Vetter <daniel@...ll.ch>,
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Subject: Re: [PATCH v2 35/65] clk: ux500: sysctrl: Add a determine_rate hook

On Thu, Nov 10, 2022 at 2:05 PM Ulf Hansson <ulf.hansson@...aro.org> wrote:
> 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?

Yeps that and a few more things, I have a scratch rewrite here:
https://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-stericsson.git/log/?h=ux500-audio-rewrite

I remember Lee said he had audio working with the mainline kernel
on Snowball at one point, unfortunately I think that was before we
started with the DT conversions and then we probably broke it.

Yours,
Linus Walleij