[ARM64][Raspberry Pi 5][RP1] Dom0 firmware clocks + RP1 OF node missing under Xen, VC4/DRM never probes

[Alap A <alumulti@xxxxxxxxx>]

Hello Xen Developers,

I am working on Xen bring-up on a Raspberry Pi 5 (BCM2712 + RP1 over PCIe) and am stuck with Dom0 firmware clocks, RP1, and VC4/DRM not probing correctly. I am hoping for guidance on the intended DT/Xen model for RP1 and Raspberry Pi firmware devices under Xen.

Setup

• Board: Raspberry Pi 5 (BCM2712, RP1 southbridge over PCIe)

• Xen: 4.17.0 (xen-troops build)

• Dom0 kernel:

  • Linux 6.19.0-rc5 (mainline)

  • Also tested Raspberry Pi downstream 6.6

• Bootloader: U-Boot

• Goal: Dom0 owns display/graphics; DomU gets a virtual display

Problem Summary

Dom0 never gets /dev/dri. The VC4/V3D/HVS DRM stack fails due to missing clocks/firmware and RP1 not binding.

Key Dom0 dmesg errors:

raspberrypi-clk soc@107c000000:firmware:clocks: probe with driver raspberrypi-clk failed with error -22
platform 1002000000.v3d: deferred probe pending: platform: supplier soc@107c000000:firmware:clocks not ready
vc4_hvs 107c580000.hvs: Couldn't get core clock
vc4-drm axi:gpu: failed to bind 107c580000.hvs (ops vc4_hvs_ops): -2
rp1_pci 0002:01:00.0: Missing of_node for device
rp1_pci 0002:01:00.0: probe with driver rp1_pci failed with error -22

As a result:

• raspberrypi-clk never binds

• firmware clock/reset providers don’t come up

• RP1 PCI device has no OF node

• VC4 DRM never probes → no /dev/dri

Device Tree / Overlay Details

Xen DT Overlay

I am using a Xen DT overlay based on xen-troops that enables HDMI, V3D, firmware, clocks, reset, vcio, and assigns devices without IOMMU. This overlay relies heavily on symbol fixups (__fixups__) and target = <0xffffffff> fragments.

Excerpt:

• Enables:

  • hdmi0, hdmi1, v3d, vc4, hvs, pixelvalve*

  • firmware, firmware_clocks, reset, vcio

  • rp1_clocks, bcm_reset, pcie_rescal

• Uses xen,force-assign-without-iommu on most nodes

(Full file: bcm2712-raspberrypi5-xen.dtso)

HDMI / Dom0 Passthrough Overlay

This overlay sets up /chosen multiboot nodes, UART for Xen console, and forces PCIe assignment.

Key parts:

dom0 {
  compatible = "multiboot,kernel\0multiboot,module";
  reg = <0x8000000 0x20000000 0x00 0x2000000>;
};

(Full file: hdmi-passthrough-dom0.dtso)

Boot Logs

Full Xen + Dom0 boot logs showing:

• raspberrypi-clk failing with -EINVAL

• rp1_pci missing of_node

• VC4/HVS/V3D deferring and timing out

(Full log: bootlogs3.txt)

Observations

1. Firmware node exists and is enabled in the DT passed to Dom0:

   /soc@107c000000/firmware {
       compatible = "raspberrypi,bcm2835-firmware", "simple-mfd";
       clocks { compatible = "raspberrypi,firmware-clocks"; status = "okay"; };
       reset  { compatible = "raspberrypi,firmware-reset";  status = "okay"; };
       vcio   { compatible = "raspberrypi,vcio";            status = "okay"; };
   };
   

   Despite this, raspberrypi-clk fails probing very early with -22.

2. RP1 enumerates correctly on PCIe:

   0002:01:00.0 Ethernet controller: Raspberry Pi Ltd RP1 PCIe 2.0 South Bridge [1de4:0001]
   

   But Linux reports:

   rp1_pci ... Missing of_node for device
   

   Which prevents:

   • rp1-clk

   • GPIO

   • reset

   • HDMI PHY

   • downstream display pipeline

3. I attempted U-Boot DT overlays to attach an OF node at:

   /axi/pcie@1000120000/pci@0,0/dev@0,0
   

   but overlays frequently fail with:

   FDT_ERR_NOTFOUND
   

   unless I rely on symbol-based fixups.

Questions

1. What is the intended DT model for RP1 under Xen on Raspberry Pi 5?

   • Should RP1 be represented as a proper OF node under the PCI endpoint in the Xen DT?

   • Or is Xen expected to synthesize this mapping internally?

2. Is raspberrypi,firmware-clocks supported in Dom0 under Xen on Pi 5?

   • The driver probes but returns -EINVAL even when the DT node exists and is enabled.

3. Are there known patches/branches for Xen or DT that enable VC4/DRM on Pi 5?

   • Specifically for firmware clocks, RP1, and HVS/V3D dependencies.

Reproduction Summary

Boot flow:

1. U-Boot loads bcm2712-rpi-5-b.dtb

2. Applies bcm2712-raspberrypi5-xen.dtbo

3. Applies hdmi-passthrough-dom0.dtbo

4. Boots Xen

5. Loads Dom0 kernel as multiboot module

Result: Dom0 boots, but RP1 and firmware clocks do not bind, so VC4/DRM never comes up.

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Any guidance on the correct DT/Xen integration model for BCM2712/RP1 would be greatly appreciated. If there is a reference DT, patch series, or recommended branch, I’d be happy to test and report back.

Best regards,
Alap