linux-kernel - Re: [PATCH v6 11/11] arm64: dts: mt7986: add BPI-R3 nand/nor overlays

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Message-ID: <CAL_JsqKiRzRToSzk3q+csWR5DEZjZpQWChqZ3mH8MLruvfe=Dw@mail.gmail.com>
Date:   Fri, 18 Nov 2022 15:39:52 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Frank Wunderlich <linux@...web.de>
Cc:     linux-mediatek@...ts.infradead.org,
        Frank Wunderlich <frank-w@...lic-files.de>,
        Ryder Lee <ryder.lee@...iatek.com>,
        Jianjun Wang <jianjun.wang@...iatek.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Kishon Vijay Abraham I <kishon@...com>,
        Vinod Koul <vkoul@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Bo Jiao <Bo.Jiao@...iatek.com>, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-phy@...ts.infradead.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH v6 11/11] arm64: dts: mt7986: add BPI-R3 nand/nor overlays

On Fri, Nov 18, 2022 at 1:01 PM Frank Wunderlich <linux@...web.de> wrote:
>
> From: Frank Wunderlich <frank-w@...lic-files.de>
>
> Add devicetree overlays for using nand and nor on BPI-R3.

Can you not tell at runtime which one you booted from? If not, how
does one choose which overlay to apply? If you can, why not populate
both nodes and enable the right one? IMO, if all h/w is present, it
should all be in the DT. Selecting what h/w to use is a separate
problem and overlays aren't a great solution for that.


> Signed-off-by: Frank Wunderlich <frank-w@...lic-files.de>
> ---
> maybe rename to dtso?
>
> "kbuild: Allow DTB overlays to built from .dtso named source files"
> https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git/commit/?h=dt/next&id=363547d2191cbc32ca954ba75d72908712398ff2
>
> more comments about the dt overlay-support:
>
> https://patchwork.kernel.org/comment/25092116/
> https://patchwork.kernel.org/comment/25085681/
> ---
> v4:
> - drop compile-comment from overlays
> - add author-information to dt-overlays
> ---
>  arch/arm64/boot/dts/mediatek/Makefile         |  2 +
>  .../mediatek/mt7986a-bananapi-bpi-r3-nand.dts | 55 +++++++++++++++
>  .../mediatek/mt7986a-bananapi-bpi-r3-nor.dts  | 69 +++++++++++++++++++
>  3 files changed, 126 insertions(+)
>  create mode 100644 arch/arm64/boot/dts/mediatek/mt7986a-bananapi-bpi-r3-nand.dts
>  create mode 100644 arch/arm64/boot/dts/mediatek/mt7986a-bananapi-bpi-r3-nor.dts
>
> diff --git a/arch/arm64/boot/dts/mediatek/Makefile b/arch/arm64/boot/dts/mediatek/Makefile
> index e8902f2cc58f..d42208c4090d 100644
> --- a/arch/arm64/boot/dts/mediatek/Makefile
> +++ b/arch/arm64/boot/dts/mediatek/Makefile
> @@ -8,6 +8,8 @@ dtb-$(CONFIG_ARCH_MEDIATEK) += mt6797-x20-dev.dtb
>  dtb-$(CONFIG_ARCH_MEDIATEK) += mt7622-rfb1.dtb
>  dtb-$(CONFIG_ARCH_MEDIATEK) += mt7622-bananapi-bpi-r64.dtb
>  dtb-$(CONFIG_ARCH_MEDIATEK) += mt7986a-bananapi-bpi-r3-emmc.dtb
> +dtb-$(CONFIG_ARCH_MEDIATEK) += mt7986a-bananapi-bpi-r3-nand.dtbo
> +dtb-$(CONFIG_ARCH_MEDIATEK) += mt7986a-bananapi-bpi-r3-nor.dtbo

These need rules to apply them to the base dtb(s). You just need:

full.dtb := base.dtb overlay.dtb
dtb-y += full.dtb

Rob