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From:   Doug Anderson <dianders@chromium.org>
Date:   Fri, 16 Nov 2018 10:23:59 -0800
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Subject: Re: [PATCH] arm64: dts: rockchip: rk3399: Add xin32k clk
To:     Derek Basehore <dbasehore@chromium.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@lists.infradead.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        devicetree@vger.kernel.org, Tony Xie <tony.xie@rock-chips.com>,
        Chris <zyw@rock-chips.com>, ayaka@soulik.info,
        "nickey.yang" <nickey.yang@rock-chips.com>,
        =?UTF-8?B?6YOR6Iic5Lm+?= <zhengsq@rock-chips.com>,
        Klaus Goger <klaus.goger@theobroma-systems.com>,
        Brian Norris <briannorris@chromium.org>,
        Enric Balletbo i Serra <enric.balletbo@collabora.com>,
        =?UTF-8?Q?Heiko_St=C3=BCbner?= <heiko@sntech.de>,
        Mark Rutland <mark.rutland@arm.com>,
        Rob Herring <robh+dt@kernel.org>
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Hi,

On Fri, Nov 16, 2018 at 9:39 AM dbasehore . <dbasehore@chromium.org> wrote:
>
> On Fri, Nov 16, 2018 at 8:01 AM Doug Anderson <dianders@chromium.org> wrote:
> >
> > Hi,
> >
> > On Thu, Nov 15, 2018 at 9:17 PM Derek Basehore <dbasehore@chromium.org> wrote:
> > >
> > > This adds the xin32k clock to the RK3399 CPU. 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.
> > >
> > > Signed-off-by: Derek Basehore <dbasehore@chromium.org>
> > > ---
> > >  arch/arm64/boot/dts/rockchip/rk3399.dtsi | 7 +++++++
> > >  1 file changed, 7 insertions(+)
> >
> > nit: I would have expected ${SUBJECT} to have v2 in it somewhere.
> >
> >
> > > diff --git a/arch/arm64/boot/dts/rockchip/rk3399.dtsi b/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> > > index 99e7f65c1779..3d09472978f8 100644
> > > --- a/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> > > +++ b/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> >
> > Aww crud.  I was at the airport yesterday and so I didn't notice that
> > you were touching rk3399, not rk3399-gru.  This belongs in the gru
> > device tree file, not in the top level rk3399.  As you have written
> > this it will break rk3399 boards that have an rk808 on them, AKA:
>
> Should this be moved to the rk3399.dtsi file? The RK3399 assumes that
> this clk exists (same as the 24MHz clk which is in rk3399.dtsi). While
> it can function without it defined, it really shouldn't. We can just
> assign the existing labels in the dts files you pointed out.

No, it should be in the board files.  Each board may produce the 32k
clock through a different component.  On gru-based devices we produce
the 32k clock through a silego part.  On some other ones we produce it
from rk808.

Technically you could say that we don't _truly_ need to model this
clock and we could have just inserted a dummy/fixed 32k clock in the
clk-rk3399.c file.  ...but we did model it so that means we should
probably model it semi-properly.

If a given board forgets to provide a 32k clock then that's a bug for
them like it was for us.

-Doug