Re: [PATCH v1 2/4] dt-bindings: clock: Add support for the MSM8998 mmcc

[Jeffrey Hugo]

On 2/5/2019 3:16 PM, Stephen Boyd wrote:
> Quoting Jeffrey Hugo (2019-02-05 14:08:43)
> > On 2/5/2019 3:02 PM, Stephen Boyd wrote:
> > > Quoting Jeffrey Hugo (2019-01-30 08:35:59)
> > > > Document the multimedia clock controller found on MSM8998
> > > >
> > > > Signed-off-by: Jeffrey Hugo <jhugo@xxxxxxxxxxxxxx>
> > > > ---
> > > >    Documentation/devicetree/bindings/clock/qcom,mmcc.txt | 7 +++++++
> > > >    1 file changed, 7 insertions(+)
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/clock/qcom,mmcc.txt b/Documentation/devicetree/bindings/clock/qcom,mmcc.txt
> > > > index 8b0f784..ae85bca 100644
> > > > --- a/Documentation/devicetree/bindings/clock/qcom,mmcc.txt
> > > > +++ b/Documentation/devicetree/bindings/clock/qcom,mmcc.txt
> > > > @@ -10,11 +10,18 @@ Required properties :
> > > >                           "qcom,mmcc-msm8960"
> > > >                           "qcom,mmcc-msm8974"
> > > >                           "qcom,mmcc-msm8996"
> > > > +                       "qcom,mmcc-msm8998"
> > > >    
> > > >    - reg : shall contain base register location and length
> > > >    - #clock-cells : shall contain 1
> > > >    - #reset-cells : shall contain 1
> > > >    
> > > > +For MSM8998 only:
> > > > +       - clocks: a list of phandles and clock-specifier pairs,
> > > > +                 one for each entry in clock-names.
> > > > +       - clock-names: "xo" for the xo clock,
> > > > +                      "gpll0" for the global pll 0 clock.
> > >
> > > Wouldn't the DSI plls also be listed here? And anything else that is
> > > external to this clock controller?
> >
> > We can't get the DSI plls from DT as far as I am aware (upstream).  That
> > is why I mentioned in the cover letter we need to rely on the global
> > namespace.
>
> Why not? Because the DSI PLL isn't a clk provider? Or it doesn't have
> #clock-cells? Please try to use the DSI PLLs from DT or at least specify
> them in the binding as optional clocks that may not matter if DSI is not
> enabled for example.

I had thought that there wasn't a DT node that exposed those (I find it 
very odd how the DSI PLLs get inited), but upon checking again, I see 
what I have missed.  I'll need to incorporate them now.

> > Also, the DSI plls, etc present a chicken and egg situation, as the plls
> > require mmcc, and mmcc requires the plls.  I forsee an unsolvable
> > EPROBE_DEFER issue.
>
> We've "solved" that problem with orphan clks and the clk parent rewrite
> series. Maybe you can try it out to help flush out any bugs lurking
> there.

Thanks for the reference in your other reply.  Will have a look.

--
Jeffrey Hugo
Qualcomm Datacenter Technologies as an affiliate of Qualcomm 
Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.