usb: cdns3: support configurations without DRD block

This series adds support for Cadence USBSSP controllers in hardware
layouts where the Dual-Role Device (DRD) register block is either
missing or inaccessible.

In such configurations, the controller is hardwired to a single role
(either host or device) and the driver must skip all OTG/DRD register
accesses to avoid bus errors or incorrect role detection.

The solution introduces a new 'cdns,no-drd' property that can be passed
via DT or software nodes. When set, the driver:
1. Skips DRD register mapping and IRQ requests.
2. Uses a different BAR indexing logic for PCI-based configurations
   (32-bit addressing layout).
3. Hardwires the role based on 'dr_mode'.

Signed-off-by: Pawel Laszczak <pawell@cadence.com>
---
Note: This series is based on current linux-next. I am aware of Peter
Chen's recent refactoring series ("usb: cdns3: plat: Expose platform
core driver as library"). Although there is a minor conflict in
cdns3-plat.c, Peter has already provided an Acked-by for this version.
I am happy to provide a rebased v8 as soon as Peter's changes land in
linux-next if required.
---
v7:
- Rename 'no_drd' to 'cdns,no-drd' (added vendor prefix).
- Update commit message to reflect property renaming and schema changes.
- Simplify 'reg-names' using a single enum for items.
- Revert 'interrupt-names' to a list of constants for strict ordering.
- Move 'reg' item descriptions to if/else blocks for better accuracy.
- Clean up 'if' logic (remove redundant 'true' check and 'dr_mode'
  requirement).
- Add explicit 'items' list for 'interrupt-names' in the 'else' block.
- Fix "uninitialized variable" warning in cdns_drd_host_on() by
  initializing 'ret' to 0.

v6:
- Fixed validation error for 'interrupt-names' by correcting
  the items definition.
- Adjusted 'minItems'/'maxItems' to properly support the optional
 'wakeup' interrupt.
- Fixed 'too long' schema error in examples.

v5:
- Implemented strict conditional validation using if-then-else logic.
- Enforced 2 register/interrupt items and required 'dr_mode'
  (host or peripheral) when 'no_drd' is present.
- Enforced the standard 3 register/interrupt items (otg, host, dev)
  when 'no_drd' is absent to ensure backward compatibility.
- Updated 'reg-names' and 'interrupt-names' to use enums in the main
  properties section to support flexible resource ordering during
  validation.

v4:
  - Added DT binding documentation for the 'no_drd' property.
  - Relaxed 'reg' and 'interrupts' requirements in the DT schema (minItems 2)
    to allow configurations where the OTG/DRD register block is missing.
  - Moved PCI_DEVICE_ID_CDNS_UDC_USBSSP from pci_ids.h to cdnsp-pci.c
    to keep the global PCI ID list clean.

v3:
  - Improved descriptions and comments for better clarity.
  - Introduced the 'no_drd' property to indicate missing DRD register block.
  - Added support for fixed host-only and device-only configurations.
  - Ensured cdns_otg_disable_irq is called only when no_drd is false.
  - Updated cdns_drd_gadget_on/off to ensure PHY mode is correctly
    handled even if DRD is disabled.

v2:
  - Changed otg_irq to be optional.
  - Added cdns->no_drd check in cdns_power_is_lost.
  - Added cdns->no_drd check in cdns_get_id.

---
Pawel Laszczak (2):
      dt-bindings: usb: cdns3: Add cdns,no-drd property
      usb: cdnsp: Add support for device-only configuration

 .../devicetree/bindings/usb/cdns,usb3.yaml         | 62 ++++++++++++++++++----
 drivers/usb/cdns3/cdns3-plat.c                     | 26 +++++----
 drivers/usb/cdns3/cdnsp-pci.c                      | 47 ++++++++++++----
 drivers/usb/cdns3/core.c                           |  3 +-
 drivers/usb/cdns3/core.h                           |  4 ++
 drivers/usb/cdns3/drd.c                            | 46 ++++++++++++++--
 6 files changed, 155 insertions(+), 33 deletions(-)
---
base-commit: e98d21c170b01ddef366f023bbfcf6b31509fa83
change-id: 20260512-b4-no_drd_config-f530f1f16d8a

Best regards,
--  
Pawel Laszczak <pawell@cadence.com>