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Date:   Fri, 18 Nov 2022 23:05:11 +0100
From:   Frank Wunderlich <frank-w@public-files.de>
To:     Rob Herring <robh+dt@kernel.org>,
        Frank Wunderlich <linux@fw-web.de>
CC:     linux-mediatek@lists.infradead.org,
        Ryder Lee <ryder.lee@mediatek.com>,
        Jianjun Wang <jianjun.wang@mediatek.com>,
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        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Chunfeng Yun <chunfeng.yun@mediatek.com>,
        Kishon Vijay Abraham I <kishon@ti.com>,
        Vinod Koul <vkoul@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Paolo Abeni <pabeni@redhat.com>,
        Lorenzo Bianconi <lorenzo@kernel.org>,
        Bo Jiao <Bo.Jiao@mediatek.com>, linux-pci@vger.kernel.org,
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Subject: Re: [PATCH v6 11/11] arm64: dts: mt7986: add BPI-R3 nand/nor overlays
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Am 18=2E November 2022 22:39:52 MEZ schrieb Rob Herring <robh+dt@kernel=2Eo=
rg>:
>On Fri, Nov 18, 2022 at 1:01 PM Frank Wunderlich <linux@fw-web=2Ede> wrot=
e:
>>
>> From: Frank Wunderlich <frank-w@public-files=2Ede>
>>
>> Add devicetree overlays for using nand and nor on BPI-R3=2E
>
>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=2E Selecting what h/w to use is a separate
>problem and overlays aren't a great solution for that=2E

It is not the decision about bootdevice,more available devices=2E

Only 1 spi device (nand OR nor) is available
at boottime as they share same spi bus and
chipselect is set via hw jumper=2E
Both nodes have reg 0,which is imho not
supported in linux=2E

I choosed overlays to add the right spi
device on the right mmc device where
similar selection happens (see patch 10)=2E
Either sd OR emmc can be used (1 mmc
controller,first 4bits from bus switched by
hardware jumper)=2EBut for mmc i use it as
base fdt because i see mmc as primary
device which holds rootfs too=2E Nand/nor is
imho helping device for accessing emmc or
like rescue system (only uboot)=2E

I probe in uboot if emmc is available (mmc
 partconf) and choose emmc else sd=2E For
 spi i try with sf command to check for nor,if
 this does not work i apply nand overlay=2E

>> Signed-off-by: Frank Wunderlich <frank-w@public-files=2Ede>
>> ---
>> maybe rename to dtso?
>>
>> "kbuild: Allow DTB overlays to built from =2Edtso named source files"
>> https://git=2Ekernel=2Eorg/pub/scm/linux/kernel/git/robh/linux=2Egit/co=
mmit/?h=3Ddt/next&id=3D363547d2191cbc32ca954ba75d72908712398ff2

Should i do this?

>> more comments about the dt overlay-support:
>>
>> https://patchwork=2Ekernel=2Eorg/comment/25092116/
>> https://patchwork=2Ekernel=2Eorg/comment/25085681/

Daniel suggest define sd/emmc as overlay too=2E=2E=2Ewith way you mention =
below we could create 4 full fdt without applying overlays in uboot=2E

>> --- a/arch/arm64/boot/dts/mediatek/Makefile
>> +++ b/arch/arm64/boot/dts/mediatek/Makefile
>> @@ -8,6 +8,8 @@ dtb-$(CONFIG_ARCH_MEDIATEK) +=3D mt6797-x20-dev=2Edtb
>>  dtb-$(CONFIG_ARCH_MEDIATEK) +=3D mt7622-rfb1=2Edtb
>>  dtb-$(CONFIG_ARCH_MEDIATEK) +=3D mt7622-bananapi-bpi-r64=2Edtb
>>  dtb-$(CONFIG_ARCH_MEDIATEK) +=3D mt7986a-bananapi-bpi-r3-emmc=2Edtb
>> +dtb-$(CONFIG_ARCH_MEDIATEK) +=3D mt7986a-bananapi-bpi-r3-nand=2Edtbo
>> +dtb-$(CONFIG_ARCH_MEDIATEK) +=3D mt7986a-bananapi-bpi-r3-nor=2Edtbo
>
>These need rules to apply them to the base dtb(s)=2E You just need:
>
>full=2Edtb :=3D base=2Edtb overlay=2Edtb
>dtb-y +=3D full=2Edtb

I would prefer to do this in bootloader to allow all 4 possible configurat=
ions:

Sd+nand
Sd+nor
Emmc+nand
Emmc+nor

>Rob

Hi,
regards Frank