Re: [PATCH v4 0/9] Improve Qualcomm EUD driver and platform support

[Elson Serrao]

On 5/1/2026 10:06 AM, Elson Serrao wrote:
> Note: This v4 revision introduces a design change compared to v3.
> Based on discussion and feedback, the binding adopts a child-node-based
> model while preserving the legacy top-level 'ports' property. The
> child-node approach is required because EUD needs a separate OF graph
> per UTMI path to accurately describe per-path role switching.
> 
> Link to the discussion leading to this decision:
> https://lore.kernel.org/all/20260324172916.804229-1-elson.serrao@xxxxxxxxxxxxxxxx/
> 


Hi Dmitry,

Just following up on this series.

Could you please take a look at the updated design and share
your feedback? Does it align with what we discussed earlier:
https://lore.kernel.org/all/20260324172916.804229-1-elson.serrao@xxxxxxxxxxxxxxxx/

Please let me know if any further changes are needed.

Thanks,
Elson


> ---
> 
> The Embedded USB Debugger (EUD) is a High-Speed USB on-chip hub that
> provides debug and trace capabilities on Qualcomm platforms. The current
> EUD driver, however, lacks essential hardware resources such as PHY
> references and support for multi-port configurations. This series
> addresses those gaps and introduces the necessary device tree updates
> to enable testing and validation of the enhanced functionality.
> 
> Below is a high-level block diagram showing the EUD and its connections.
> 
> 
> 			              EUD Block
>  	                   +------------------------------+  
> 			   |                              |
> [Conn-0]-->[USB2PHY-0]---->|-------- Path 0 --------------|-->[USBCtrl-0]
> 			   |                              |  
> [Conn-1]-->[USB2PHY-1]---->|-------- Path 1 --------------|-->[USBCtrl-1]
> 			   |                              |
> 			   |      +------------------+    |
> 			   |      |  EUD Debug Hub   |    |
> 			   |      +------------------+    |
> 			   +------------------------------+
> 
> This work builds upon an earlier EUD driver submission:
> https://lore.kernel.org/all/20240730222439.3469-1-quic_eserrao@xxxxxxxxxxx/
> and extends it with support for multi-port use cases and proper handling
> of EUD operation across different USB roles.
> 
> The series has been validated on the Qualcomm Dragonwing Q6 platform
> (RB3 Gen2 board), confirming successful OpenOCD connectivity to the EUD
> interface. For detailed usage instructions, refer to Qualcomm’s Linux
> kernel debugging guide:
> https://docs.qualcomm.com/bundle/publicresource/topics/80-70020-12/debugging_linux_kernel.html#debug-using-openocd
> 
> ---
> Changes in v4:
> - [Patch 0001] Restructure the flattened ports representation to a child-node
>   based model.
>   - Preserve the top-level 'ports' property and add per-path child nodes,
>     so that each role-switch path is described using its own OF graph.
>     (Dmitry).
>   - Link to the discussion leading to this design decision:
>     https://lore.kernel.org/all/20260324172916.804229-1-elson.serrao@xxxxxxxxxxxxxxxx/
> - [Patch 0002] Use explicit port names when selecting the active EUD
>   port (Greg)
> - [Patch 0003] Use a scoped iterator when looping over child nodes and
>   drop redundant EUD path validation checks (Konrad). Preserve support
>   for the legacy top-level ports description.
> - [Patch 0004] Register role switch per path and forward the role switch
>   notifications to the USB controller.
> - [Patch 0006]  Add host mode co-ordination based on the role changes as
>   per the new design and drop the custom API that was used to get role
>   notifications.
> - [Patch 0008] Described the UTMI path as a child node with role switch
>   capability.
> - Link to v3: https://lore.kernel.org/all/20260309203337.803986-1-elson.serrao@xxxxxxxxxxxxxxxx/
> 
> Changes in RFC v3:
> - Replaced the per-path (eud-path@N) model with a flattened ports
>   representation based on the feedback.
> - Added port@2 and port@3 to support dual-port configurations.
> - Removed the EUD-local 'phys' and 'usb-role-switch' properties since PHY
>   and role-switch information is obtained from walking the OF graph.
> - Updated PHY discovery logic by fetching the PHY from the controller
>   node/fwnode, and exported a new API for the controller to report role
>   changes. The dwc3-qcom driver now uses this API to notify EUD on role
>   transitions.
> - Updated the DTS structure by moving the EUD-to-controller port mapping
>   into the base SoC DTSI, enabling EUD by default, and adjusting all board
>   DTS files accordingly, including adding the usb-role-switch provider
>   link on connector nodes.
> - Link to v2: https://lore.kernel.org/all/20260126233830.2193816-1-elson.serrao@xxxxxxxxxxxxxxxx/
> 
> Changes in v2:
> - Improved commit message of patch 0001 and 0003 with historical context
>   on why EUD worked without PHY references on single-path systems.
>   Expanded the usb-role-switch property description in the bindings file.
> - Link to v1: https://lore.kernel.org/all/20260116232106.2234978-1-elson.serrao@xxxxxxxxxxxxxxxx/
> ---
> 
> Elson Serrao (9):
>   dt-bindings: soc: qcom: eud: Add per-path child nodes for UTMI routing
>   usb: misc: qcom_eud: add sysfs attribute for port selection
>   usb: misc: qcom_eud: add per-path High-Speed PHY control
>   usb: misc: qcom_eud: add per-path role switch support
>   usb: misc: qcom_eud: improve enable_store API
>   usb: misc: qcom_eud: add host mode coordination
>   usb: misc: qcom_eud: fix virtual attach/detach event handling
>   arm64: dts: qcom: kodiak: Describe EUD UTMI path using child node
>   arm64: dts: qcom: Map USB connector to EUD on Kodiak boards
> 
>  Documentation/ABI/testing/sysfs-driver-eud    |  16 +
>  .../bindings/soc/qcom/qcom,eud.yaml           |  55 ++-
>  arch/arm64/boot/dts/qcom/kodiak.dtsi          |  35 +-
>  .../boot/dts/qcom/qcm6490-fairphone-fp5.dts   |  10 +-
>  .../dts/qcom/qcm6490-particle-tachyon.dts     |  10 +-
>  .../boot/dts/qcom/qcm6490-shift-otter.dts     |  10 +-
>  arch/arm64/boot/dts/qcom/qcs6490-rb3gen2.dts  |  10 +-
>  .../dts/qcom/qcs6490-thundercomm-rubikpi3.dts |  10 +-
>  .../boot/dts/qcom/sm7325-nothing-spacewar.dts |  10 +-
>  drivers/usb/misc/qcom_eud.c                   | 346 ++++++++++++++++--
>  10 files changed, 446 insertions(+), 66 deletions(-)
>