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

[Frank Wunderlich]

Hi

> Gesendet: Sonntag, 20. November 2022 um 17:12 Uhr
> Von: "Rob Herring" <robh at kernel.org>
> On Sat, Nov 19, 2022 at 08:19:52AM +0100, Frank Wunderlich wrote:
> > Am 8. November 2022 15:45:49 MEZ schrieb Rob Herring <robh+dt at kernel.org>:
> > >On Fri, Nov 18, 2022 at 4:05 PM Frank Wunderlich
> > ><frank-w at public-files.de> wrote:
> > >>
> > >> Am 18. November 2022 22:39:52 MEZ schrieb Rob Herring <robh+dt at kernel.org>:
> > >> >On Fri, Nov 18, 2022 at 1:01 PM Frank Wunderlich <linux at fw-web.de> wrote:
> > >> >>
> > >> >> From: Frank Wunderlich <frank-w at public-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.
> > >>
> > >> It is not the decision about bootdevice,more available devices.
> > >>
> > >> Only 1 spi device (nand OR nor) is available
> > >> at boottime as they share same spi bus and
> > >> chipselect is set via hw jumper.
> > >> Both nodes have reg 0,which is imho not
> > >> supported in linux.
> > >
> > >As long as one is set to disabled, it should be fine.
> > >
> > >
> > >> I choosed overlays to add the right spi
> > >> device on the right mmc device where
> > >> similar selection happens (see patch 10).
> > >> Either sd OR emmc can be used (1 mmc
> > >> controller,first 4bits from bus switched by
> > >> hardware jumper).But for mmc i use it as
> > >> base fdt because i see mmc as primary
> > >> device which holds rootfs too. Nand/nor is
> > >> imho helping device for accessing emmc or
> > >> like rescue system (only uboot).
> > >
> > >No way to read the jumper state or know what you booted from I gues?
> > >
> > >> I probe in uboot if emmc is available (mmc
> > >>  partconf) and choose emmc else sd. For
> > >>  spi i try with sf command to check for nor,if
> > >>  this does not work i apply nand overlay.
> > >
> > >Instead of applying overlays, wouldn't just changing 'status' be easier?
> >
> > It will be easier,but requires dts for all
> >  combinations,we have have sd/emmc
> >  combination twice (once for nand
> >  enabling,once for nor) and we have then 4
> >  full dts instead of smaller overlays in fit.
>
> No, I mean can't you have 1 dtb with everything, but nand, nor, emmc,
> and sd are all disabled. Then at boot change 'status' for what's
> enabled.

at least for sd/emmc: no, as they share same mmc-node with different settings (bus-width,speed,...).

for nand/nor i'm not sure if spi can have 2 childs with same unit-address/reg even if disabled.
Then i do not know how to enable a dts-node in uboot...only know (not long time) how to apply overlay ;)

> > So i should add spi subnodes both disabled
> >  in base dtsi and create 4 dts (sd-nand,sd-nor,emmc-nand,emmc-nor) with
> >  mmc node and enabling the right spi node?
> > >>
> > >> >> Signed-off-by: Frank Wunderlich <frank-w at public-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
> > >>
> > >> Should i do this?
> > >
> > >Yes. .dts -> .dtbo is going to be removed.
> >
> > Do this if still using overlays,will test new way.
> >
> > Maybe we can apply parts 1-9 first?
>
> Sure.

i would wait for them applied before posting next version, i hope they can go into 6.2. Then it is easier because depencies are all in.

overlay was only for discussion the right way...my preferred way was mmc in board dts and spi as overlay,
daniel preferred base fdt without them all and 4 overlays. another way already discussed were 4 full fdt, but
how to get all 4 combinations with less files and not defining mmc/spi device twice? i see only the overlay
version and combining via Makefile.

what is your preferred way (except all devices in 1 dts which is afair not possible, daniel please correct me if
i'm wrong)?

> >
> > >> >> more comments about the dt overlay-support:
> > >> >>
> > >> >> https://patchwork.kernel.org/comment/25092116/
> > >> >> https://patchwork.kernel.org/comment/25085681/
> > >>
> > >> Daniel suggest define sd/emmc as overlay too...with way you mention below we could create 4 full fdt without applying overlays in uboot.
> > >
> > >Yes, but if you are going to do that, then you can just do all this
> > >with includes.
> >
> > This is a third way if i understand correctly
> >
> > Make all of them as overlay (dtso?) but
> >  build dtb by combining them in makefile.
> >
> > This looks the best way because it avoids
> >  redundand code for mmc node and allows
> >  my current spi config (not the status way
> >  which may break due to same unit address).
> >
> > I guess my base dtsi is then a dts too?
>
> Yes, it can be.
>
> >
> > Or should these overlays only duplicated and either include sd dts or emmc dts (but this creates again redundant code)?
> > >> >> --- 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
> > >>
> > >> I would prefer to do this in bootloader to allow all 4 possible configurations:
> > >>
> > >> Sd+nand
> > >> Sd+nor
> > >> Emmc+nand
> > >> Emmc+nor
> > >
> > >That's fine. The purpose here is to document what the overlays apply
> > >to, check that they actually apply, and validate them when applied
> > >(unless someone wants to figure out all the issues with validating
> > >just an overlay and make that work). You for example have an
> > >undocumented compatible in yours (denx,fit).
> >
> > Oh,need to check,copied partitions from my
> >  uboot dts...maybe there is a linux version
> >  for marking it as fit partition,else i drop
> >  completely.
>
> You just need to document it. But the first thing I'm going to say, is
> 'u-boot' is the vendor, not 'denx'. So 'u-boot,fit'.

imho it is not needed in linux, so i drop it.

regards Frank