Re: [PATCH v4 1/7] dt-bindings: clk: at91: add an I2S mux clock

[Codrin Ciubotariu]

On 31.05.2018 18:56, Rob Herring wrote:
> On Thu, May 31, 2018 at 10:31 AM, Stephen Boyd <sboyd@xxxxxxxxxx> wrote:
> > Quoting Rob Herring (2018-05-31 07:20:57)
> > > On Thu, May 31, 2018 at 5:25 AM, Codrin Ciubotariu
> > > <codrin.ciubotariu@xxxxxxxxxxxxx> wrote:
> > > > On 31.05.2018 03:58, Rob Herring wrote:
> > > > > On Fri, May 25, 2018 at 03:34:22PM +0300, Codrin Ciubotariu wrote:
> > > > > > The I2S mux clock can be used to select the I2S input clock. The
> > > > > > available parents are the peripheral and the generated clocks.
> > > > > >
> > > > > > Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@xxxxxxxxxxxxx>
> > > > > > ---
> > > > > >    .../devicetree/bindings/clock/at91-clock.txt       | 34
> > > > > > ++++++++++++++++++++++
> > > > > >    1 file changed, 34 insertions(+)
> > > > > >
> > > > > > diff --git a/Documentation/devicetree/bindings/clock/at91-clock.txt
> > > > > > b/Documentation/devicetree/bindings/clock/at91-clock.txt
> > > > > > index 51c259a..1c46b3c 100644
> > > > > > --- a/Documentation/devicetree/bindings/clock/at91-clock.txt
> > > > > > +++ b/Documentation/devicetree/bindings/clock/at91-clock.txt
> > > > > > @@ -90,6 +90,8 @@ Required properties:
> > > > > >          "atmel,sama5d2-clk-audio-pll-pmc"
> > > > > >                  at91 audio pll output on AUDIOPLLCLK that feeds the PMC
> > > > > >                  and can be used by peripheral clock or generic clock
> > > > > > +       "atmel,sama5d2-clk-i2s-mux":
> > > > > > +               at91 I2S clock source selection
> > > > >
> > > > >
> > > > > Is this boolean or takes some values. If latter, what are valid values?
> > > >
> > > >
> > > > This is the compatible string of the clock driver.
> > >
> > > Ah, now I remember. AT91 uses fine grained clock nodes in DT. Is there
> > > still a plan to fix this?
> >
> > I'm also interested in a plan.
> >
> > > > > > +               compatible = "atmel,sama5d2-clk-i2s-mux";
> > > > > > +               #address-cells = <1>;
> > > > > > +               #size-cells = <0>;
> > > > >
> > > > >
> > > > > How do you address this block? My guess is you don't because it is just
> > > > > part of some other block and you are just creating this node to
> > > > > instantiate a driver. Just make the node for the actual h/w block a
> > > > > clock provider and define the clock ids (0 and 1).
> > > >
> > > >
> > > > This block is not addressed, but its children are. The register we access in
> > > > this driver is not part of other block. It's a SFR register, accessed
> > > > through syscon and it has nothing to do with the I2S IP (see SAMA5D2 DS,
> > > > page 1256, fig. 44-1: I2SC Block Diagram) that is the consumer of this
> > > > clock. Adding a clock-id property in the I2S node would be just like v3 of
> > > > this series, with the difference that we use clock-id instead of alias id to
> > > > set the clock parent, which is not how you suggested back then.
> > >
> > > I wasn't suggesting a clock-id property, but a clock specifier (i.e.
> > > make #clock-cells 1).
> > >
> > > But AT91 clocks are all a mess, so I don't know what to tell you.
> >
> > If #clock-cells of 1 works then we should go with that. It's still weird
> > that we need random nodes to add more clks, but I guess that's how it's
> > going to be for each at91 clk driver until it changes to be one big
> > provider node.
>
> Seems to me that clock additions could use a new binding and we start
> with a new driver that handles these few clocks initially. But I
> haven't looked whether both can coexist.

Mark already applied to broonie/sound.git the I2S bindings that have a 
phandle to this clock. If I am to change #clock-cells to 1, I will have 
to change the bindings to include the clock-id.
Which approach should I take now?

Thanks and best regards,
Codrin