linux-kernel - Re: [PATCH 01/22] arm64: dts: qcom: sm8150: add base dts file

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Date:   Wed, 14 Aug 2019 10:44:39 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Stephen Boyd <sboyd@...nel.org>
Cc:     Andy Gross <agross@...nel.org>, Vinod Koul <vkoul@...nel.org>,
        linux-arm-msm@...r.kernel.org, sibis@...eaurora.org,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/22] arm64: dts: qcom: sm8150: add base dts file

On Wed 14 Aug 09:58 PDT 2019, Stephen Boyd wrote:

> Quoting Vinod Koul (2019-08-14 05:49:51)
> > diff --git a/arch/arm64/boot/dts/qcom/sm8150.dtsi b/arch/arm64/boot/dts/qcom/sm8150.dtsi
[..]
> > +       clocks {
> > +               xo_board: xo-board {
> > +                       compatible = "fixed-clock";
> > +                       #clock-cells = <0>;
> > +                       clock-frequency = <19200000>;
> 
> Is it 19.2 or 38.4 MHz? It seems like lately there are dividers, but I
> guess it doesn't really matter in the end.
> 

As with previous platforms, the board's XO feeds the PMIC at 38.4MHz and
the SoC's CXO_IN pin (i.e. bi_tcxo) is fed from the PMIC's LNBBCLK1,
which is ticking at 19.2MHz.

[..]
> > +               gcc: clock-controller@...000 {
> > +                       compatible = "qcom,gcc-sm8150";
> > +                       reg = <0x00100000 0x1f0000>;
> > +                       #clock-cells = <1>;
> > +                       #reset-cells = <1>;
> > +                       #power-domain-cells = <1>;
> > +                       clock-names = "bi_tcxo", "sleep_clk";
> > +                       clocks = <&xo_board>, <&sleep_clk>;

So this first one should actually be <&rpmhcc LNBBCLK1>.

But while we now should handle this gracefully in the clock driver I
think we still have problems with the cascading probe deferral that
follows - last time I tried to do this the serial driver probe deferred
past user space initialization and the system crashed as we didn't have
a /dev/console.

So, I think we should s/xo_board/lnbbclk1/ (at 19.2MHz) to make it
represent the schematics and then once we have rpmhcc and validated that
the system handles this gracefully we can switch it out.

Regards,
Bjorn