[PATCH RFC net-next 0/9] net: introduce Qualcomm XPCS support and add Nord Ethernet plumbing

Hi,

This is an early RFC which adds the XPCS and ETHQOS plumbing required
to enable 10 Gigabit Ethernet on the Qualcomm Nord SoC. This is the
first time USXGMII together with an external PCS is being supported by
the dwmac-qcom-ethqos driver.

This platform was somewhat tricky to work on, with several new pieces
having to come together across the MAC, XPCS and SerDes layers. Any
feedback would be appreciated, particularly around the XPCS modelling
and the generic stmmac register-layout changes.

The overall hardware path looks like this:

  +------------------+      +------------------+      +------------------+      +------------------+
  |    DW25GMAC      | ---> |  Synopsys XPCS   | ---> | QCOM SGMII PHY   | ===> | Ext PHY / Switch |
  | + QCOM ETHQOS    |      | + QCOM wrapper   |      |    (SerDes)      |      | USX/10GBASE-R    |
  +------------------+      +------------------+      +------------------+      +------------------+

The series can be broadly divided into two areas:

1. Qualcomm XPCS support

Nord integrates a Synopsys DesignWare XPCS, but exposes the PCS,
PMA/PMD and MII MMD register regions through separate direct-MMIO
windows instead of the standard contiguous or indirect XPCS mappings.
Patches 1 through 5 add the binding, generic platform register-access
hooks, the Qualcomm MMD-to-MMIO translation, and the runtime-PM handling
needed for the CSR clock.

The XPCS also uses Clause 37 control and status for USXGMII, while the
generic XPCS support currently handles USXGMII using Clause 73. Patch 2
adds the required Clause 37 USXGMII configuration and link-state path.

Using a small Qualcomm-specific access layer around the existing XPCS
core was the most straightforward way I could find to model this IP.
The core already uses synthetic IDs for the NXP integrations and has
vendor-specific hooks for other XPCS implementations, so this series
follows a similar approach. I am very much open to suggestions if there
is a cleaner way to represent the non-standard register mapping.

2. DW25GMAC and Qualcomm ETHQOS support

Patches 6 through 9 add the Nord ETHQOS binding and driver support. The
Nord integration has sparse, platform-specific MTL queue and DMA channel
addresses, as well as a relocated timestamp register bank. The series
therefore adds optional XGMAC register-layout data while preserving the
standard layout for existing platforms.

The ETHQOS driver then selects the XPCS provided through pcs-handle and
adds the Nord wrapper programming required for USXGMII, including the
EEE clock vote needed for PCS link-up and the platform-specific SerDes
loopback control.

This series has an obvious dependency on Jitendra Vegiraju's DW25GMAC
work:
https://lore.kernel.org/netdev/20260402213629.1996133-1-jitendra.vegiraju@broadcom.com/ (local)

I understand that a v10 of that series is planned. While bringing up
Nord, I also needed a few fixes on top of the DW25GMAC series. Those are
not included here; I will share them separately with Jitendra in case
they are useful for the next revision.

Testing:
Initial testing was done on the Nord Ride SX platform, where both
Ethernet ports connect to the on-board MV-Q6223 switch using fixed-link
USXGMII at 10 Gbps. The testing tree included the DW25GMAC dependency
and the additional fixups mentioned above.

Signed-off-by: Mohd Ayaan Anwar <mohd.anwar@oss.qualcomm.com>
---
Mohd Ayaan Anwar (9):
      dt-bindings: net: pcs: add Qualcomm Nord XPCS
      net: pcs: xpcs: add USXGMII Clause 37 autoneg support
      net: pcs: xpcs: add custom platform register accessors
      net: pcs: xpcs: add Qualcomm Nord platform support
      net: pcs: xpcs: initialize runtime PM as suspended
      dt-bindings: net: qcom,ethqos: add Qualcomm Nord
      net: stmmac: support custom XGMAC register layouts
      net: stmmac: qcom-ethqos: support external PCS
      net: stmmac: qcom-ethqos: add Qualcomm Nord support

 .../devicetree/bindings/net/pcs/snps,dw-xpcs.yaml  |  17 +++
 .../devicetree/bindings/net/qcom,ethqos.yaml       |  57 ++++++--
 .../devicetree/bindings/net/snps,dwmac.yaml        |   2 +
 drivers/net/ethernet/stmicro/stmmac/common.h       |   1 +
 .../ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c    | 162 ++++++++++++++++++++-
 .../net/ethernet/stmicro/stmmac/dwmac-socfpga.c    |   2 +-
 drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h     |  94 ++++++++----
 .../net/ethernet/stmicro/stmmac/dwxgmac2_core.c    |  34 +++--
 drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c | 128 +++++++++-------
 drivers/net/ethernet/stmicro/stmmac/hwif.c         |   5 +-
 .../net/ethernet/stmicro/stmmac/stmmac_ethtool.c   |   5 +-
 drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c   |  15 +-
 drivers/net/pcs/Makefile                           |   3 +-
 drivers/net/pcs/pcs-xpcs-plat.c                    |  47 +++++-
 drivers/net/pcs/pcs-xpcs-qcom.c                    |  86 +++++++++++
 drivers/net/pcs/pcs-xpcs-qcom.h                    |  16 ++
 drivers/net/pcs/pcs-xpcs.c                         | 126 ++++++++++++++++
 drivers/net/pcs/pcs-xpcs.h                         |  15 ++
 include/linux/pcs/pcs-xpcs.h                       |   2 +
 include/linux/stmmac.h                             |  11 ++
 20 files changed, 707 insertions(+), 121 deletions(-)
---
base-commit: 6598456d72e48d779445bfec8f72114747f8b8d7
change-id: 20260923-qcom_xpcs_nord_emac-bf296eb48e4b

Best regards,
-- 
Mohd Ayaan Anwar [off-list ref]