Bug#883580: debian-installer: arm64: please ship dtb files

[Ian Campbell]

On Wed, 2017-12-06 at 07:53 +0100, Andre Heider wrote:
> 
> I don't know what devices you work on, but I have a couple of different 
> consumer armhf and arm64 devices, spread out over different 
> architectures. All their device trees are updated every single kernel 
> release. Often it's for new drivers like mmc, pci, net, dri etc., which 
> obviously the installer could make use of. Bindings are merged with the 
> driver, so of course I want the dtb matching its kernel!

Note also that at least some ARM subarch maintainers explicitly require
that the DTB should be kept in sync with the kernel, i.e. that newer
kernels may not necessarily work with older dtbs (that is kernel
supplied ones, quite apart from what the manufacturer may have
provided):

http://lists.infradead.org/pipermail/linux-arm-kernel/2015-October/373922.html

Ian.

Bug#883580: debian-installer: arm64: please ship dtb files

[Hermann Lauer]

Hello All,

On Tue, Dec 05, 2017 at 10:47:12PM +0100, Karsten Merker wrote:
> > Please don't ship dtb files at all, including the kernel images.
...
> it appears to me that this argument assumes a situation that we
> simply don't have for many devices.  A lot of the ARM-based
> devices that Debian supports don't come with any preinstalled
> firmware at all.  Many of them don't even have permanent onboard
> storage (such as an SPI NOR flash) in which such a firmware could
> be stored, so the firmware is commonly a user-supplied u-boot
> image on an SD card.
> 
> In practice, for most of the devices supported by Debian/armhf,
> the canonical source for the devicetree _is_ the Linux kernel. 
> The SoC-manufacturers commonly ship years-old, often
> pre-devicetree android kernels and stone-aged hacked-up u-boot
> versions without any notion of device-tree for their hardware and
> don't really care about mainline Linux.  ...
+1

And additionally fiddling with devicetree should be encouraged IMHO as
it allows to do unusual things with those SoC boards, eg. sharing
an IR RX with an UART TX - how should the vendor decide in such cases ?

Also look at the ACPI situation - even main Server vendors firmware
contains bugs not fixed during the livetime of the systems.

So please let the linux kernel tree be the device-tree reference.
Thanks for all the work on device-tree,
 greetings
  Hermann

-- 
Netzwerkadministration/Zentrale Dienste, Interdiziplinaeres 
Zentrum fuer wissenschaftliches Rechnen der Universitaet Heidelberg
IWR; INF 205; 69120 Heidelberg; Tel: (06221)54-14405 Fax: -14427
Email: hermann.la...@iwr.uni-heidelberg.de

Bug#883580: debian-installer: arm64: please ship dtb files

[Andre Heider]

On Tue, 5 Dec 2017 14:07:46 + Leif Lindholm 
 wrote:

Please don't ship dtb files at all, including the kernel images.

If firmware does not come with hardware description, that is a
shortcoming of the firmware. If a newer kernel cannot be booted with
an existing device tree, then that is a bug and the kernel should be
patched.


Ok, so in your world a distribution should not ship any dtb files, 
because the manufacturer's firmware is bug-free and feature complete on 
day one.


That's nice, but doesn't sound like the real world at all.

> By all means, put a tree of verified actually working device trees
> somewhere for platforms known to be provided with bad versions from
> their manufacturer.

That tree is the sum of the dtb files of the corresponding kernel, which 
this bug report is about. Those may not adhere to your definition of 
verified, but please don't forget that there're two separate worlds out 
there: upstream and downstream. Debian's current way of booting a kernel 
release with its dtb ensures those world never collide, and I think that 
is a very wise choice.


I don't know what devices you work on, but I have a couple of different 
consumer armhf and arm64 devices, spread out over different 
architectures. All their device trees are updated every single kernel 
release. Often it's for new drivers like mmc, pci, net, dri etc., which 
obviously the installer could make use of. Bindings are merged with the 
driver, so of course I want the dtb matching its kernel!

Bug#883580: debian-installer: arm64: please ship dtb files

[Leif Lindholm]

X-Debbugs-CC: glik...@secretlab.ca

Please don't ship dtb files at all, including the kernel images.

If firmware does not come with hardware description, that is a
shortcoming of the firmware. If a newer kernel cannot be booted with
an existing device tree, then that is a bug and the kernel should be
patched.

By all means, put a tree of verified actually working device trees
somewhere for platforms known to be provided with bad versions from
their manufacturer.

Bug#883580: debian-installer: arm64: please ship dtb files

[Andre Heider]

Source: debian-installer

Some arm64 devices (like espressobin) boot using u-boot and not using 
efi. For these the kernel's corresponding dtb is required to boot.


I only checked the latest daily netboot.tar.gz, and while armhf ships 
those files, arm64 does not.


When fishing out the dtb out of the binary kernel package and using that 
for netboot, the installer works just fine - including its flash-kernel 
run, which makes the freshly installed system bootable using dtb.