linux-kernel - Re: [PATCH 7/7] arm64: dts: qcom: sc7180: Use 'ranges' in arm,armv7-timer-mem node

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Message-ID: <CAD=FV=UGRqeAr8vVUfx3ADyxNLJRz3g=YhWNX1adgepx_kADrA@mail.gmail.com>
Date:   Mon, 16 Dec 2019 22:14:35 -0800
From:   Doug Anderson <dianders@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Vinod Koul <vkoul@...nel.org>,
        Kiran Gunda <kgunda@...eaurora.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Sandeep Maheswaram <sanm@...eaurora.org>,
        Amit Kucheria <amit.kucheria@...aro.org>,
        Maulik Shah <mkshah@...eaurora.org>,
        Taniya Das <tdas@...eaurora.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH 7/7] arm64: dts: qcom: sc7180: Use 'ranges' in
 arm,armv7-timer-mem node

Hi,

On Thu, Dec 12, 2019 at 1:55 PM Stephen Boyd <swboyd@...omium.org> wrote:
>
> Quoting Douglas Anderson (2019-12-12 11:35:43)
> > Running `make dtbs_check` yells:
> >
> >   arch/arm64/boot/dts/qcom/sc7180-idp.dt.yaml: timer@...20000: #size-cells:0:0: 1 was expected
> >
> > It appears that someone was trying to assert the fact that sub-nodes
> > describing frames would never have a size that's more than 32-bits
> > big.  That's certainly true in the case of sc7180.
> >
> > I guess this is a hint that it's time to do the thing that nobody
> > seems to do but that "writing-bindings.txt" says we should all do.
> > Specifically it says: "DO use non-empty 'ranges' to limit the size of
> > child buses/devices".  That means we should probably limit the
>
> It got cut off here. I'm waiting to find out what it is!!

I was going to say that I should use ranges to limit the address cells
in addition to the size cells, but then I think I must have got
distracted and forgot to finish my


> > I believe that this patch is the way to do it and there should be no
> > bad side effects here.  I believe that since we're far enough down
> > (not trying to describe an actual device, just some sub-pieces) that
> > this won't cause us to run into the problems that caused us to
> > increase the soc-level #address-cells and #size-cells to 2 in sdm845
> > in commit bede7d2dc8f3 ("arm64: dts: qcom: sdm845: Increase address
> > and size cells for soc").
> >
> > I can at least confirm that "arch_mem_timer" seems to keep getting
> > interrupts in "/proc/interrupts" after this change.
> >
> > Fixes: 90db71e48070 ("arm64: dts: sc7180: Add minimal dts/dtsi files for SC7180 soc")
> > Signed-off-by: Douglas Anderson <dianders@...omium.org>
> > ---
>
> This pattern exists in most of the qcom dts files. Can you fix all the
> arm,armv7-timer-mem nodes. Maybe the binding has the same problem too in
> the example.

Yeah.  I'm a little scared to go and do this for every qcom device
tree file since I have no good way to test them, but I suppose I can
give it a shot.  I was kinda thinking that, in general, it would make
sense for folks to tackle one SoC at a time and make that SoC clean
and test it.

In any case, your idea about updating the example seemed wise to me,
so I sent out:

https://lore.kernel.org/r/20191216220512.1.I7dbd712cfe0bdf7b53d9ef9791072b7e9c6d3c33@changeid

I'll put this patch on hold until Rob gives his thoughts on that one
so we can really make sure we're supposed to be using ranges in this
way.

-Doug