On 12/11/2025 10:35, Chen-Yu Tsai wrote:

On Wed, Nov 12, 2025 at 4:14 PM Krzysztof Kozlowski [off-list ref] wrote:

quoted

On 11/11/2025 20:22, Douglas Anderson wrote:

quoted

Add barebones device trees for frankel (Pixel 10), blazer (Pixel 10
Pro), and mustang (Pixel 10 Pro XL). These device trees are enough to
boot to a serial prompt using an initramfs.

Many things can be noted about these device trees:

1. They are organized as "dts" files for the main SoC and "dtso"
   overlays for the boards. There is discussion about this in the
   bindings patch ("dt-bindings: arm: google: Add bindings for
   frankel/blazer/mustang").
2. They won't boot with the currently shipping bootloader. The current
   bootloader hardcodes several paths to nodes that it wants to update
   and considers it a fatal error if it can't find these nodes.
   Interested parties will need to wait for fixes to land and a new
   bootloader to be rolled out before attempting to use these.
3. They only add one revision (MP1) of each of frankel, blazer, and
   mustang. With this simple barebones device tree, there doesn't
   appear to be any difference between the revisions. More revisions
   will be added as needed in the future. The heuristics in the
   bootloader will pick the MP1 device tree if there are not any
   better matches.
4. They only add the dts for the B0 SoC for now. The A0 SoC support
   can be added later if we find the need.
5. Even newer versions of the bootloader will still error out if they
   don't find a UFS node to add calibration data to. Until UFS is
   supported, we provide a bogus UFS node for the bootloader. While
   the bootloader could be changed, there is no long-term benefit
   since eventually the device tree will have a UFS node.
6. They purposely choose to use the full 64-bit address and size cells
   for the root node and the `soc@0` node. Although I haven't tested
   the need for this, I presume the arguments made in commit
   bede7d2dc8f3 ("arm64: dts: qcom: sdm845: Increase address and size
   cells for soc") would apply here.
7. Though it looks as if the UART is never enabled, the bootloader
   knows to enable the UART when the console is turned on. Baud rate
   is configurable in the bootloader so is never hardcoded in the
   device tree.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---
To avoid fragmenting the discussion, IMO:
* Let's have the discussion about using the "dts" for SoC and the
  "dtso" for the boards in response to the bindings (patch #1).

That's discussion here, bindings are irrelevant to this.

quoted

* If we want to have a discussion about putting "board-id" and
  "model-id" at the root of the board overlays, we can have it
  here. I'll preemptively note that the "board-id" and "model-id"
  won't show up in the final combined device tree and they are just
  used by the tool (mkdtimg). We could change mkdtimg to parse the
  "compatible" strings of the overlays files (since I've put the IDs
  there too), but official the docs [1] seem to indicate that
  top-level properties like this are OK.

In order for these device trees to pass validation without warnings,
it's assumed you have my dtc patches:
* https://lore.kernel.org/r/20251110204529.2838248-1-dianders@chromium.org (local)
* https://lore.kernel.org/r/20251110204529.2838248-2-dianders@chromium.org (local)

[1] https://git.kernel.org/pub/scm/utils/dtc/dtc.git/tree/Documentation/dt-object-internal.txt?h=main

 arch/arm64/boot/dts/google/Makefile           |   9 +
 arch/arm64/boot/dts/google/lga-b0.dts         | 391 ++++++++++++++++++
 .../arm64/boot/dts/google/lga-blazer-mp1.dtso |  22 +
 .../boot/dts/google/lga-frankel-mp1.dtso      |  22 +
 .../boot/dts/google/lga-mustang-mp1.dtso      |  22 +
 .../boot/dts/google/lga-muzel-common.dtsi     |  17 +
 6 files changed, 483 insertions(+)
 create mode 100644 arch/arm64/boot/dts/google/lga-b0.dts
 create mode 100644 arch/arm64/boot/dts/google/lga-blazer-mp1.dtso
 create mode 100644 arch/arm64/boot/dts/google/lga-frankel-mp1.dtso
 create mode 100644 arch/arm64/boot/dts/google/lga-mustang-mp1.dtso
 create mode 100644 arch/arm64/boot/dts/google/lga-muzel-common.dtsi

diff --git a/arch/arm64/boot/dts/google/Makefile b/arch/arm64/boot/dts/google/Makefile
index a6b187e2d631..276001e91632 100644
--- a/arch/arm64/boot/dts/google/Makefile
+++ b/arch/arm64/boot/dts/google/Makefile

@@ -1 +1,10 @@
 # SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause)
+
+dtb-$(CONFIG_ARCH_GOOGLE) += \
+     lga-blazer-mp1.dtb \
+     lga-frankel-mp1.dtb \
+     lga-mustang-mp1.dtb
+
+lga-blazer-mp1-dtbs          := lga-b0.dtb lga-blazer-mp1.dtbo
+lga-frankel-mp1-dtbs         := lga-b0.dtb lga-frankel-mp1.dtbo
+lga-mustang-mp1-dtbs         := lga-b0.dtb lga-mustang-mp1.dtbo

diff --git a/arch/arm64/boot/dts/google/lga-b0.dts b/arch/arm64/boot/dts/google/lga-b0.dts
new file mode 100644
index 000000000000..83c2db4f20ef
--- /dev/null
+++ b/arch/arm64/boot/dts/google/lga-b0.dts

@@ -0,0 +1,391 @@
+// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
+/*
+ * Google Tensor G5 (laguna) SoC rev B0
+ *
+ * Copyright 2024-2025 Google LLC.
+ */
+
+/dts-v1/;
+
+#include <dt-bindings/interrupt-controller/arm-gic.h>
+#include <dt-bindings/interrupt-controller/irq.h>
+
+/ {
+     model = "Google Tensor G5 rev B0";
+     compatible = "google,soc-id-0005-rev-10", "google,lga";

So that's SoC, thus must not be a DTS file, but DTSI.

...


...

quoted

diff --git a/arch/arm64/boot/dts/google/lga-frankel-mp1.dtso b/arch/arm64/boot/dts/google/lga-frankel-mp1.dtso
new file mode 100644
index 000000000000..133494de7a9b
--- /dev/null
+++ b/arch/arm64/boot/dts/google/lga-frankel-mp1.dtso

And that's a board, so DTS.

quoted

@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
+/*
+ * Google Pixel 10 (frankel) MP 1
+ *
+ * Copyright 2024-2025 Google LLC.
+ */
+
+/dts-v1/;
+/plugin/;
+
+#include "lga-muzel-common.dtsi"
+
+/ {
+     board-id = <0x070306>;
+     board-rev = <0x010000>;

Undocumented ABI, which you cannot document because these properties are
not allowed. You cannot have them.

This is part of the discussion I want to have at Plumbers. But I suppose
we can start here.

Then the patch should be called RFC as not yet ready for merging. :)

The Android DTB partition format uses six 32-bit integers for matching,
as opposed to a compatible string used in FIT images. Two of the integers
are the "id" and "rev" numbers in the example above. The remaining four
are custom and left up to the (vendor) bootloader implementation.

The values for these fields need to be stored somewhere with the .dts.
The compiled DTB is useless if the user cannot build a proper image for
the bootloader to consume, and that involves putting in the right numbers
in these fields. The android "mkdtimg" tool can either take the values
from some known properties within the DTB, or have them fed to it
externally.

So if we don't want these numbers in the dts itself, then we should come
up with some format to store them beside the dts files.

Re-iterating comment from Rob long time ago: adding such new properties
is fine, but they must come for more than one user and be universal
across these users.

And of course the ABI needs to be documented which did not happen here.

I indeed said incorrectly that "properties are not allowed". The
properties could be allowed if we document them according to above Rob's
comment, but that did not happen.

Adding these properties per one SoC vendor is not really allowed, like
qcom,board-id and qcom,msm-id, but maybe you intend to make it generic.

On a similar note, we would have a similar problem with FIT images and
overlays. The FIT image format maps a (series of) compatible string(s)
to one DTB and any number of overlays. If overlays are involved, then
the compatible string cannot come from the DTB itself, and the mapping
must be stored somewhere.

I recall, although cannot find now references to, a email talk on the
list saying that such overlays should have their own compatible, thus
solving this mapping problem.


Best regards,
Krzysztof