Re: incompatible device trees between u-boot and linux

Re: incompatible device trees between u-boot and linux

[Tom Rini]

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On Wed, Aug 25, 2021 at 06:12:20PM +0300, Vladimir Oltean wrote:
> On Wed, Aug 25, 2021 at 10:26:10AM -0400, Tom Rini wrote:
> > On Wed, Aug 25, 2021 at 05:18:16PM +0300, Vladimir Oltean wrote:
> > > On Wed, Aug 25, 2021 at 10:00:45AM -0400, Tom Rini wrote:
> > > > On Wed, Aug 25, 2021 at 03:58:10PM +0200, Michael Walle wrote:
> > > >
> > > > > Hi,
> > > > >
> > > > > I noticed that there is a fallback to the u-boot device tree for linux
> > > > > (esp. EFI boot) if no other device tree was found, see [1]. It seems this
> > > > > is working fine for imx devices, for example, where you can just boot a
> > > > > stock installer iso via EFI. It will just work and it is quite a nice
> > > > > feature as a fallback.
> > > > >
> > > > > Now for the layerscape architecture, the ls1028a in my case, things are
> > > > > more difficult because the bindings differ between u-boot and linux - one
> > > > > which comes to mind is DSA and ethernet.
> > > > >
> > > > > Which begs the general question, is it encouraged to have both bindings
> > > > > diverge? To me it seems, that most bindings in u-boot are ad-hoc and there
> > > > > is no real review or alignment but just added as needed, which is ok if
> > > > > they are local to u-boot. But since they are nowadays passed to linux
> > > > > (by default!) I'm not so sure anymore.
> > > > >
> > > > > OTOH The whole structure around a .dts{,i} and -u-boot.dtsi looks like
> > > > > they should (could?) be shared between linux and u-boot.
> > > > >
> > > > > -michael
> > > > >
> > > > > [1]
> > > > > https://elixir.bootlin.com/u-boot/v2021.10-rc2/source/common/board_r.c#L471
> > > >
> > > > The U-Boot device tree is supposed to be able to be passed on to Linux
> > > > and Just Work.  The bindings are not supposed to be different between
> > > > the two (except for when we take the binding while it's being hashed out
> > > > upstream BUT THEN RESYNCED).
> > >
> > > You might need to spell that out a bit clearer.
> > >
> > > You are saying that both U-Boot and Linux are allowed to have their own
> > > custom properties (like 'u-boot,dm-spl' for U-Boot, and 'managed = "in-band-status"'
> > > for Linux), as long as the device tree files themselves are in sync, and
> > > the subset of the device tree blob understood by Linux (i.e. the U-Boot
> > > blob sans the U-Boot specifics) is compatible with the Linux DT blob?
> >
> > I don't know what about the Linux example makes it Linux specific.  But
> > yes, 'u-boot,dm-spl' is clearly in our namespace and should be ignored
> > by Linux.  The whole reason we have the -u-boot.dtsi automatic drop-in
> > logic (as much as it can be used is that device trees are device trees
>         ^
>         I don't think this parenthesis ever closes...

Ah, whoops.  Should have been "(as much as it can be used)" because it
does get #included instead in some cases, for reasons.

> 
> > and describe the hardware and developers don't need to write a device
> > tree for Linux and a device tree for U-Boot and a device tree for
> > FreeBSD and ...  So yes, you're supposed to use the device tree for a
>                 ^
>                 so I never get the answer to "the whole reason is...".
> 
> > platform and it works here and there and every where.
> 
> The fact that only Linux uses it makes it Linux specific.
> 
> > > To expand even further on that, it means we should put 'managed = "in-band-status"'
> > > in U-Boot, which is a Linux phylink device tree property, even if U-Boot
> > > does not use phylink?
> >
> > We should be able to drop in the device trees from Linux and use them.
> > Custodians should be re-syncing them periodically.  Some are, even.
> 
> Are you ready to take up device tree bindings for PTP timers, PCIe root
> complex event collectors, cascaded interrupt controllers, things which
> U-Boot will never ever need to support?
> 
> At least in Linux there is a policy to not add device tree nodes that do
> not have drivers. Is the same policy not true for U-Boot? At least your
> ./scripts/checkpatch.pl does have the same "check for DT compatible
> documentation" section as Linux. You might consider removing it if you
> want people to not strip the DTs they submit to U-Boot.
> 
> And why do we even maintain the device tree bindings in Linux at all?
> It seems rather counter-productive for both ends to do that, if it is
> expected that the kernel works with DT blobs provided by third parties too,
> and if all third parties need to resync with it (there are other boot
> loaders too beyond U-Boot, and other kernels beyond Linux). Somehow it
> doesn't feel right for the reference to be the Linux kernel. Maybe this
> is something that needs to be brought up with higher-level Linux maintainers.
> 
> I have no problem at all with structuring the device tree in the same
> way in U-Boot as in Linux, as long as that proves to not be a foolish
> endeavor.

DT is ABI is hardware description and OS-agnostic has been the rule for
10+ years.  If that's no longer the case, can someone please tell me?

-- 
Tom

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Re: incompatible device trees between u-boot and linux

[Vladimir Oltean]

On Wed, Aug 25, 2021 at 11:24:08AM -0400, Tom Rini wrote:
> On Wed, Aug 25, 2021 at 06:12:20PM +0300, Vladimir Oltean wrote:
> > On Wed, Aug 25, 2021 at 10:26:10AM -0400, Tom Rini wrote:
> > > On Wed, Aug 25, 2021 at 05:18:16PM +0300, Vladimir Oltean wrote:
> > > > On Wed, Aug 25, 2021 at 10:00:45AM -0400, Tom Rini wrote:
> > > > > On Wed, Aug 25, 2021 at 03:58:10PM +0200, Michael Walle wrote:
> > > > >
> > > > > > Hi,
> > > > > >
> > > > > > I noticed that there is a fallback to the u-boot device tree for linux
> > > > > > (esp. EFI boot) if no other device tree was found, see [1]. It seems this
> > > > > > is working fine for imx devices, for example, where you can just boot a
> > > > > > stock installer iso via EFI. It will just work and it is quite a nice
> > > > > > feature as a fallback.
> > > > > >
> > > > > > Now for the layerscape architecture, the ls1028a in my case, things are
> > > > > > more difficult because the bindings differ between u-boot and linux - one
> > > > > > which comes to mind is DSA and ethernet.
> > > > > >
> > > > > > Which begs the general question, is it encouraged to have both bindings
> > > > > > diverge? To me it seems, that most bindings in u-boot are ad-hoc and there
> > > > > > is no real review or alignment but just added as needed, which is ok if
> > > > > > they are local to u-boot. But since they are nowadays passed to linux
> > > > > > (by default!) I'm not so sure anymore.
> > > > > >
> > > > > > OTOH The whole structure around a .dts{,i} and -u-boot.dtsi looks like
> > > > > > they should (could?) be shared between linux and u-boot.
> > > > > >
> > > > > > -michael
> > > > > >
> > > > > > [1]
> > > > > > https://elixir.bootlin.com/u-boot/v2021.10-rc2/source/common/board_r.c#L471
> > > > >
> > > > > The U-Boot device tree is supposed to be able to be passed on to Linux
> > > > > and Just Work.  The bindings are not supposed to be different between
> > > > > the two (except for when we take the binding while it's being hashed out
> > > > > upstream BUT THEN RESYNCED).
> > > >
> > > > You might need to spell that out a bit clearer.
> > > >
> > > > You are saying that both U-Boot and Linux are allowed to have their own
> > > > custom properties (like 'u-boot,dm-spl' for U-Boot, and 'managed = "in-band-status"'
> > > > for Linux), as long as the device tree files themselves are in sync, and
> > > > the subset of the device tree blob understood by Linux (i.e. the U-Boot
> > > > blob sans the U-Boot specifics) is compatible with the Linux DT blob?
> > >
> > > I don't know what about the Linux example makes it Linux specific.  But
> > > yes, 'u-boot,dm-spl' is clearly in our namespace and should be ignored
> > > by Linux.  The whole reason we have the -u-boot.dtsi automatic drop-in
> > > logic (as much as it can be used is that device trees are device trees
> >         ^
> >         I don't think this parenthesis ever closes...
>
> Ah, whoops.  Should have been "(as much as it can be used)" because it
> does get #included instead in some cases, for reasons.
>
> >
> > > and describe the hardware and developers don't need to write a device
> > > tree for Linux and a device tree for U-Boot and a device tree for
> > > FreeBSD and ...  So yes, you're supposed to use the device tree for a
> >                 ^
> >                 so I never get the answer to "the whole reason is...".
> >
> > > platform and it works here and there and every where.
> >
> > The fact that only Linux uses it makes it Linux specific.
> >
> > > > To expand even further on that, it means we should put 'managed = "in-band-status"'
> > > > in U-Boot, which is a Linux phylink device tree property, even if U-Boot
> > > > does not use phylink?
> > >
> > > We should be able to drop in the device trees from Linux and use them.
> > > Custodians should be re-syncing them periodically.  Some are, even.
> >
> > Are you ready to take up device tree bindings for PTP timers, PCIe root
> > complex event collectors, cascaded interrupt controllers, things which
> > U-Boot will never ever need to support?
> >
> > At least in Linux there is a policy to not add device tree nodes that do
> > not have drivers. Is the same policy not true for U-Boot? At least your
> > ./scripts/checkpatch.pl does have the same "check for DT compatible
> > documentation" section as Linux. You might consider removing it if you
> > want people to not strip the DTs they submit to U-Boot.
> >
> > And why do we even maintain the device tree bindings in Linux at all?
> > It seems rather counter-productive for both ends to do that, if it is
> > expected that the kernel works with DT blobs provided by third parties too,
> > and if all third parties need to resync with it (there are other boot
> > loaders too beyond U-Boot, and other kernels beyond Linux). Somehow it
> > doesn't feel right for the reference to be the Linux kernel. Maybe this
> > is something that needs to be brought up with higher-level Linux maintainers.
> >
> > I have no problem at all with structuring the device tree in the same
> > way in U-Boot as in Linux, as long as that proves to not be a foolish
> > endeavor.
>
> DT is ABI is hardware description and OS-agnostic has been the rule for
> 10+ years.  If that's no longer the case, can someone please tell me?

So if Michael's board with DT provided by U-Boot doesn't work for some
stupid reason like "Linux expects the pcie node to be under /soc", or
"Linux wants all PCIe BARs of a RCIEP ECAM to be spelled out in the
'ranges' property, because it's too dumb to detect them itself", or
something like that, I've got no argument against that, let's go ahead
and resync U-Boot with Linux.

But "DT is ABI is hardware description" is a pretty vague truism that
does not actually help here.

Will you accept device trees with devices for which a driver will never
probe in U-Boot, and will you remove the checkpatch warnings about those,
to not discourage people from submitting them prior to the actual public
review?

If a U-Boot driver will be written for a device that does not have a
driver yet in Linux, then the Linux driver will be written but with
DT bindings incompatible with what was established in U-Boot, will you
wake up the U-Boot developer from the grave and ask them to resync the
driver to follow Linux? Or will you accept drivers at all for hardware
that is not supported by Linux?

I also think there are various degrees of what it means "to work" with a
device tree provided directly by U-Boot. Distros like Arch Linux ARM
have a package for device tree blobs, and it is expected that these are
updated by the distro, and U-Boot just loads them. As Michael points out,
the DT provided by U-Boot is just a fallback. The OS should boot to
prompt and have a network connection to set itself up properly again.
But we need to draw a harder line on what we _actually_ desire to work
beyond that.

Re: incompatible device trees between u-boot and linux

[Tom Rini]

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On Wed, Aug 25, 2021 at 06:43:23PM +0300, Vladimir Oltean wrote:
> On Wed, Aug 25, 2021 at 11:24:08AM -0400, Tom Rini wrote:
> > On Wed, Aug 25, 2021 at 06:12:20PM +0300, Vladimir Oltean wrote:
> > > On Wed, Aug 25, 2021 at 10:26:10AM -0400, Tom Rini wrote:
> > > > On Wed, Aug 25, 2021 at 05:18:16PM +0300, Vladimir Oltean wrote:
> > > > > On Wed, Aug 25, 2021 at 10:00:45AM -0400, Tom Rini wrote:
> > > > > > On Wed, Aug 25, 2021 at 03:58:10PM +0200, Michael Walle wrote:
> > > > > >
> > > > > > > Hi,
> > > > > > >
> > > > > > > I noticed that there is a fallback to the u-boot device tree for linux
> > > > > > > (esp. EFI boot) if no other device tree was found, see [1]. It seems this
> > > > > > > is working fine for imx devices, for example, where you can just boot a
> > > > > > > stock installer iso via EFI. It will just work and it is quite a nice
> > > > > > > feature as a fallback.
> > > > > > >
> > > > > > > Now for the layerscape architecture, the ls1028a in my case, things are
> > > > > > > more difficult because the bindings differ between u-boot and linux - one
> > > > > > > which comes to mind is DSA and ethernet.
> > > > > > >
> > > > > > > Which begs the general question, is it encouraged to have both bindings
> > > > > > > diverge? To me it seems, that most bindings in u-boot are ad-hoc and there
> > > > > > > is no real review or alignment but just added as needed, which is ok if
> > > > > > > they are local to u-boot. But since they are nowadays passed to linux
> > > > > > > (by default!) I'm not so sure anymore.
> > > > > > >
> > > > > > > OTOH The whole structure around a .dts{,i} and -u-boot.dtsi looks like
> > > > > > > they should (could?) be shared between linux and u-boot.
> > > > > > >
> > > > > > > -michael
> > > > > > >
> > > > > > > [1]
> > > > > > > https://elixir.bootlin.com/u-boot/v2021.10-rc2/source/common/board_r.c#L471
> > > > > >
> > > > > > The U-Boot device tree is supposed to be able to be passed on to Linux
> > > > > > and Just Work.  The bindings are not supposed to be different between
> > > > > > the two (except for when we take the binding while it's being hashed out
> > > > > > upstream BUT THEN RESYNCED).
> > > > >
> > > > > You might need to spell that out a bit clearer.
> > > > >
> > > > > You are saying that both U-Boot and Linux are allowed to have their own
> > > > > custom properties (like 'u-boot,dm-spl' for U-Boot, and 'managed = "in-band-status"'
> > > > > for Linux), as long as the device tree files themselves are in sync, and
> > > > > the subset of the device tree blob understood by Linux (i.e. the U-Boot
> > > > > blob sans the U-Boot specifics) is compatible with the Linux DT blob?
> > > >
> > > > I don't know what about the Linux example makes it Linux specific.  But
> > > > yes, 'u-boot,dm-spl' is clearly in our namespace and should be ignored
> > > > by Linux.  The whole reason we have the -u-boot.dtsi automatic drop-in
> > > > logic (as much as it can be used is that device trees are device trees
> > >         ^
> > >         I don't think this parenthesis ever closes...
> >
> > Ah, whoops.  Should have been "(as much as it can be used)" because it
> > does get #included instead in some cases, for reasons.
> >
> > >
> > > > and describe the hardware and developers don't need to write a device
> > > > tree for Linux and a device tree for U-Boot and a device tree for
> > > > FreeBSD and ...  So yes, you're supposed to use the device tree for a
> > >                 ^
> > >                 so I never get the answer to "the whole reason is...".
> > >
> > > > platform and it works here and there and every where.
> > >
> > > The fact that only Linux uses it makes it Linux specific.
> > >
> > > > > To expand even further on that, it means we should put 'managed = "in-band-status"'
> > > > > in U-Boot, which is a Linux phylink device tree property, even if U-Boot
> > > > > does not use phylink?
> > > >
> > > > We should be able to drop in the device trees from Linux and use them.
> > > > Custodians should be re-syncing them periodically.  Some are, even.
> > >
> > > Are you ready to take up device tree bindings for PTP timers, PCIe root
> > > complex event collectors, cascaded interrupt controllers, things which
> > > U-Boot will never ever need to support?
> > >
> > > At least in Linux there is a policy to not add device tree nodes that do
> > > not have drivers. Is the same policy not true for U-Boot? At least your
> > > ./scripts/checkpatch.pl does have the same "check for DT compatible
> > > documentation" section as Linux. You might consider removing it if you
> > > want people to not strip the DTs they submit to U-Boot.
> > >
> > > And why do we even maintain the device tree bindings in Linux at all?
> > > It seems rather counter-productive for both ends to do that, if it is
> > > expected that the kernel works with DT blobs provided by third parties too,
> > > and if all third parties need to resync with it (there are other boot
> > > loaders too beyond U-Boot, and other kernels beyond Linux). Somehow it
> > > doesn't feel right for the reference to be the Linux kernel. Maybe this
> > > is something that needs to be brought up with higher-level Linux maintainers.
> > >
> > > I have no problem at all with structuring the device tree in the same
> > > way in U-Boot as in Linux, as long as that proves to not be a foolish
> > > endeavor.
> >
> > DT is ABI is hardware description and OS-agnostic has been the rule for
> > 10+ years.  If that's no longer the case, can someone please tell me?
> 
> So if Michael's board with DT provided by U-Boot doesn't work for some
> stupid reason like "Linux expects the pcie node to be under /soc", or
> "Linux wants all PCIe BARs of a RCIEP ECAM to be spelled out in the
> 'ranges' property, because it's too dumb to detect them itself", or
> something like that, I've got no argument against that, let's go ahead
> and resync U-Boot with Linux.
> 
> But "DT is ABI is hardware description" is a pretty vague truism that
> does not actually help here.

I'm saying that because it's what's been said for what feels like 10+
years.  I don't want to think how many countless hours have been spent
on that point at conferences over the years.  It's not even a Linux
thing.  I would swear you can (or could, unless it got broken) take the
same DTB for some platforms and boot Linux or FreeBSD or some other BSD
or maybe even VxWorks and it works.

> Will you accept device trees with devices for which a driver will never
> probe in U-Boot,

Yes, I will absolutely take device trees that have devices we don't need
in U-Boot since the point is, and many SoC vendors are doing (and the
ones that aren't are, I am not happy about / with) right now.

> and will you remove the checkpatch warnings about those,
> to not discourage people from submitting them prior to the actual public
> review?

With respect to checkpatch.pl, maybe I'm just missing the line in
question?  Or maybe it's a kernel-related warning we need to disable in
our .checkpatch.conf.  But I don't want to side-track over this part.

> If a U-Boot driver will be written for a device that does not have a
> driver yet in Linux, then the Linux driver will be written but with
> DT bindings incompatible with what was established in U-Boot, will you
> wake up the U-Boot developer from the grave and ask them to resync the
> driver to follow Linux? Or will you accept drivers at all for hardware
> that is not supported by Linux?

What I've said for years (but yes, I've missed changes, maybe the yaml
dt binding stuff would help so I could make CI fail or at least require
manual override?) is that U-Boot will take immature bindings but it's on
the developer to re-sync once the bindings are fully reviewed.  This is
to help with the chicken-and-egg problem.  But old bindings are not
intended to be supported, once it's finalized.  That is part of the
bargain.

> I also think there are various degrees of what it means "to work" with a
> device tree provided directly by U-Boot. Distros like Arch Linux ARM
> have a package for device tree blobs, and it is expected that these are
> updated by the distro, and U-Boot just loads them. As Michael points out,
> the DT provided by U-Boot is just a fallback. The OS should boot to
> prompt and have a network connection to set itself up properly again.
> But we need to draw a harder line on what we _actually_ desire to work
> beyond that.

Every distribution has a package for device tree binaries, because
that's how you get a device tree on the still vast majority of platforms
that don't ship one in-flash (RPis being the modern exception) and to my
knowledge none of them are happy about having to build and pass and make
sure the right one is used on a given board at boot.  So yes, U-Boot
being able to pass a device tree on to the next stage is one of those
things to help everything Just Work and be boring.

-- 
Tom

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Re: incompatible device trees between u-boot and linux

[Vladimir Oltean]

On Wed, Aug 25, 2021 at 04:09:50PM -0400, Tom Rini wrote:
> I'm saying that because it's what's been said for what feels like 10+
> years.  I don't want to think how many countless hours have been spent
> on that point at conferences over the years.  It's not even a Linux
> thing.  I would swear you can (or could, unless it got broken) take the
> same DTB for some platforms and boot Linux or FreeBSD or some other BSD
> or maybe even VxWorks and it works.

So I absolutely do not oppose the greater goal, and if you say that
other silicon vendors do it, then shame on us really, NXP should step up
their game and be way stricter during internal review and such for things
that matter.

I'm afraid it's something that must trickle down from the management and
maintainership level before it could be effective.

In any case, it doesn't sound absurd at all, with a bit of passion it
could be done on all Layerscapes. I would be absolutely glad to help on
the Ethernet / DSA side of things (which I believe is the reason why
Michael summoned me into this thread), but I don't believe that's where
the problem is right now. When I added the DM_DSA uclass to U-Boot I did
my best to pick a reasonable subset of Linux DSA, and with compatible
device tree bindings. Also maintaining the Linux side of things, I did
provide feedback to Tim Harvey for the Microchip KSZ switches as to
what is the subset supported by U-Boot that would also be DT-compatible
with Linux. If it turns out that I failed at that, I am willing to
rework what we have.

I have been known on a few occasions to say "U-Boot does not parse this
part of the device tree, you can just strip it away", but I will keep my
mouth shut from now on.

Re: incompatible device trees between u-boot and linux

[Michael Walle]

Am 2021-08-26 01:03, schrieb Vladimir Oltean:
> On Wed, Aug 25, 2021 at 04:09:50PM -0400, Tom Rini wrote:
> In any case, it doesn't sound absurd at all, with a bit of passion it
> could be done on all Layerscapes. I would be absolutely glad to help on
> the Ethernet / DSA side of things (which I believe is the reason why
> Michael summoned me into this thread),

;) and because I thought you might be interested in the answer to the
initial question. After all, you also worked on the device trees in 
linux
and u-boot.

> but I don't believe that's where
> the problem is right now. When I added the DM_DSA uclass to U-Boot I 
> did
> my best to pick a reasonable subset of Linux DSA, and with compatible
> device tree bindings. Also maintaining the Linux side of things, I did
> provide feedback to Tim Harvey for the Microchip KSZ switches as to
> what is the subset supported by U-Boot that would also be DT-compatible
> with Linux. If it turns out that I failed at that, I am willing to
> rework what we have.

I started to convert the u-boot device tree yesterday - and it doesn't
look too bad for now. I was already able to copy the kernel soc dtsi
and u-boot is still booting and working.

Theres still one catch at the moment, AFAIK in linux you can put the
PHYs either in the mdio controller node or in a "mdio" subnode within
the ethernet controller node. I'm not sure wether the latter works in
u-boot, but [1] looks promising. At least, linux dtbs are using the
mdio subnodes and u-boot put the phys into the mdio controller node.

Maybe sharing the device tree between linux and u-boot isn't that hard
for the ls1028a after all and its just that nobody did it for now.
Renaming the reference here and there and introducing the linux
compatible strings may do it. I'll come back to you if there are
problems with ethernet (or DSA).

-michael

> I have been known on a few occasions to say "U-Boot does not parse this
> part of the device tree, you can just strip it away", but I will keep 
> my
> mouth shut from now on.

[1] https://lists.denx.de/pipermail/u-boot/2020-May/410169.html

Re: incompatible device trees between u-boot and linux

[Vladimir Oltean]

On Thu, Aug 26, 2021 at 09:35:12AM +0200, Michael Walle wrote:
> Am 2021-08-26 01:03, schrieb Vladimir Oltean:
> > On Wed, Aug 25, 2021 at 04:09:50PM -0400, Tom Rini wrote:
> > In any case, it doesn't sound absurd at all, with a bit of passion it
> > could be done on all Layerscapes. I would be absolutely glad to help on
> > the Ethernet / DSA side of things (which I believe is the reason why
> > Michael summoned me into this thread),
> 
> ;) and because I thought you might be interested in the answer to the
> initial question. After all, you also worked on the device trees in linux
> and u-boot.
> 
> > but I don't believe that's where
> > the problem is right now. When I added the DM_DSA uclass to U-Boot I did
> > my best to pick a reasonable subset of Linux DSA, and with compatible
> > device tree bindings. Also maintaining the Linux side of things, I did
> > provide feedback to Tim Harvey for the Microchip KSZ switches as to
> > what is the subset supported by U-Boot that would also be DT-compatible
> > with Linux. If it turns out that I failed at that, I am willing to
> > rework what we have.
> 
> I started to convert the u-boot device tree yesterday - and it doesn't
> look too bad for now. I was already able to copy the kernel soc dtsi
> and u-boot is still booting and working.
> 
> Theres still one catch at the moment, AFAIK in linux you can put the
> PHYs either in the mdio controller node or in a "mdio" subnode within
> the ethernet controller node. I'm not sure wether the latter works in
> u-boot, but [1] looks promising. At least, linux dtbs are using the
> mdio subnodes and u-boot put the phys into the mdio controller node.

Please change Linux for that, move the PHYs from the per-port MDIO node
to the PF 3 central MDIO controller node. Due to hardware reasons, the
per-port MDIO controller registers are in fact de-featured and should be
hidden from new LS1028A reference manuals.

> Maybe sharing the device tree between linux and u-boot isn't that hard
> for the ls1028a after all and its just that nobody did it for now.
> Renaming the reference here and there and introducing the linux
> compatible strings may do it. I'll come back to you if there are
> problems with ethernet (or DSA).
> 
> -michael
> 
> > I have been known on a few occasions to say "U-Boot does not parse this
> > part of the device tree, you can just strip it away", but I will keep my
> > mouth shut from now on.
> 
> [1] https://lists.denx.de/pipermail/u-boot/2020-May/410169.html

Re: incompatible device trees between u-boot and linux

[Michael Walle]

Am 2021-08-26 18:32, schrieb Vladimir Oltean:
> On Thu, Aug 26, 2021 at 09:35:12AM +0200, Michael Walle wrote:
>> Theres still one catch at the moment, AFAIK in linux you can put the
>> PHYs either in the mdio controller node or in a "mdio" subnode within
>> the ethernet controller node. I'm not sure wether the latter works in
>> u-boot, but [1] looks promising. At least, linux dtbs are using the
>> mdio subnodes and u-boot put the phys into the mdio controller node.
> 
> Please change Linux for that, move the PHYs from the per-port MDIO node
> to the PF 3 central MDIO controller node. Due to hardware reasons, the
> per-port MDIO controller registers are in fact de-featured and should 
> be
> hidden from new LS1028A reference manuals.

Care to share some more details? There should be some more information
besides "for hardware reasons" which should go into the commit message.
Is there an erratum?

In fact, I guess in Rev0 of the RM it has already been removed, at least
from the port memory map (in the RevB RM it was still present).

-michael

Re: incompatible device trees between u-boot and linux

[Vladimir Oltean]

On Sun, Aug 29, 2021 at 01:12:30AM +0200, Michael Walle wrote:
> Am 2021-08-26 18:32, schrieb Vladimir Oltean:
> > On Thu, Aug 26, 2021 at 09:35:12AM +0200, Michael Walle wrote:
> > > Theres still one catch at the moment, AFAIK in linux you can put the
> > > PHYs either in the mdio controller node or in a "mdio" subnode within
> > > the ethernet controller node. I'm not sure wether the latter works in
> > > u-boot, but [1] looks promising. At least, linux dtbs are using the
> > > mdio subnodes and u-boot put the phys into the mdio controller node.
> >
> > Please change Linux for that, move the PHYs from the per-port MDIO node
> > to the PF 3 central MDIO controller node. Due to hardware reasons, the
> > per-port MDIO controller registers are in fact de-featured and should be
> > hidden from new LS1028A reference manuals.
>
> Care to share some more details? There should be some more information
> besides "for hardware reasons" which should go into the commit message.
> Is there an erratum?
>
> In fact, I guess in Rev0 of the RM it has already been removed, at least
> from the port memory map (in the RevB RM it was still present).
>
> -michael

It's a long and boring explanation, PM sent.