linux-kernel - Re: [PATCH] arm64: dts: rockchip: Add 32k clk on rk3399-gru

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Date:   Wed, 28 Nov 2018 14:45:59 +0100
From:   Heiko Stübner <heiko@...ech.de>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Derek Basehore <dbasehore@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        devicetree@...r.kernel.org, Tony Xie <tony.xie@...k-chips.com>,
        Chris <zyw@...k-chips.com>, ayaka@...lik.info,
        "nickey.yang" <nickey.yang@...k-chips.com>,
        郑舜乾 <zhengsq@...k-chips.com>,
        Klaus Goger <klaus.goger@...obroma-systems.com>,
        Brian Norris <briannorris@...omium.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH] arm64: dts: rockchip: Add 32k clk on rk3399-gru

Am Mittwoch, 28. November 2018, 01:42:36 CET schrieb Doug Anderson:
> Hi,
> 
> On Tue, Nov 27, 2018 at 3:23 PM Derek Basehore <dbasehore@...omium.org> 
wrote:
> > This adds the 32k clock to the RK3399 Gru board file. Even though it's
> > not directly used, muxes will end up traversing the entire clk tree on
> > calls to determine_rate if it doesn't exist. This is because the 32k
> > clk is listed as a possible parent on some clks. Since the clk doesn't
> > know about the 32k clk (it was never registered), it triggers a global
> > search for it. This can happen about 40 times per second, which isn't
> > great for power.
> 
> I seem to remember Heiko requesting something be added to the commit
> 
> message.  Ah yes, he said:
> > That would also be a great part of the commit message, like
> > "...on Gru boards the 32kHz clock gets produced by a Silego oscillator"
> > or so when you move it over to rk3399-gru.dtsi .
> 
> Presumably Heiko could add that to the commit message when he applies
> the patch, so maybe wait to see if he wants you to respin it?
> 
> > Signed-off-by: Derek Basehore <dbasehore@...omium.org>
> > ---
> > 
> >  arch/arm64/boot/dts/rockchip/rk3399-gru.dtsi | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/arch/arm64/boot/dts/rockchip/rk3399-gru.dtsi
> > b/arch/arm64/boot/dts/rockchip/rk3399-gru.dtsi index
> > ca07f6032200..a07aa4c570c0 100644
> > --- a/arch/arm64/boot/dts/rockchip/rk3399-gru.dtsi
> > +++ b/arch/arm64/boot/dts/rockchip/rk3399-gru.dtsi
> > @@ -14,6 +14,13 @@
> > 
> >                 stdout-path = "serial2:115200n8";
> >         
> >         };
> > 
> > +       ap_rtc_clk: ap-rtc-clk {
> > +               compatible = "fixed-clock";
> > +               clock-frequency = <32768>;
> > +               clock-output-names = "xin32k";
> > +               #clock-cells = <0>;
> > +       };
> > +
> > 
> >         /*
> >         
> >          * Power Tree
> 
> Really this should be below the power tree, AKA right above
> "gpio-keys".  Convention has typically been that only "special" nodes
> like "chosen" go all the way at the top here.  Then the power tree
> (parents first), then other nodes.
> 
> In the Chrome OS tree we had an "/* END REGULATORS */ comment to try
> to separate out the power tree from the rest of the nodes, but I guess
> Heiko didn't like that when this went upstream so now you just have to
> know the convention.  :-P
> 
> Possibly Heiko would re-sort this for you himself when applying the
> change if he agrees with my understanding of the conventions.

We hashed out the dt-conventions somewhat together during veyron
times, so I'd be surprised if we didn't agree on them :-D .

In any case, I've adapted the commit message to add the Silego part,
moved the clock to the correct position and applied the result with
your Reviewed-by for 4.21.


Heiko