linux-kernel - Re: [PATCH 1/2] arm64: dts: mt8173: elm: Set uart0 to mmio32 iotype

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Message-ID: <CAJMQK-gVO53a1SnsjsJPu-ZR-NoNb4TGXrOpb-naD71pmjExCw@mail.gmail.com>
Date:   Thu, 10 Sep 2020 16:44:39 +0800
From:   Hsin-Yi Wang <hsinyi@...omium.org>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Devicetree List <devicetree@...r.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] arm64: dts: mt8173: elm: Set uart0 to mmio32 iotype

On Thu, Sep 10, 2020 at 4:16 PM Enric Balletbo i Serra
<enric.balletbo@...labora.com> wrote:
>
> Hi Hsin-Yi,
>
> On 10/9/20 9:57, Hsin-Yi Wang wrote:
> > On Thu, Sep 10, 2020 at 3:20 PM Enric Balletbo i Serra
> > <enric.balletbo@...labora.com> wrote:
> >>
> >> Hi Hsin-Yi,
> >>
> >> On 10/9/20 7:46, Hsin-Yi Wang wrote:
> >>> Set uart0 iotype to mmio32 to make earlycon work with stdout-path.
> >>>
> >>> Signed-off-by: Hsin-Yi Wang <hsinyi@...omium.org>
> >>> ---
> >>>  arch/arm64/boot/dts/mediatek/mt8173-elm.dtsi | 2 ++
> >>>  1 file changed, 2 insertions(+)
> >>>
> >>> diff --git a/arch/arm64/boot/dts/mediatek/mt8173-elm.dtsi b/arch/arm64/boot/dts/mediatek/mt8173-elm.dtsi
> >>> index a5a12b2599a4a..d54e62f72c65d 100644
> >>> --- a/arch/arm64/boot/dts/mediatek/mt8173-elm.dtsi
> >>> +++ b/arch/arm64/boot/dts/mediatek/mt8173-elm.dtsi
> >>> @@ -1160,6 +1160,8 @@ &thermal {
> >>>  };
> >>>
> >>>  &uart0 {
> >>> +     reg-io-width = <4>;
> >>> +     reg-shift = <2>;
> >>
> >> I am wondering if these properties are common enough to go to mt8173.dtsi
> >> instead of here.
> >>
> > Since stdout-path is set on elm.dtsi (using uart0), so I add this
> > attribute here.
> >
>
> Why needs to be defined in the same place that stdout-path is set?
>
> My guess is that reg-io-width and reg-shift are SoC specific, as they define how
> the IO access to the register is done. In fact, I think that these properties
> should be added in all the uarts, not only the one that has defined the stdout-path.
>
Okay, I'll apply them to all uart. Thanks.