[PATCH v3 0/7] PCI: endpoint: Remote DMA support via vNTB

Hi,

This series lets an RC use endpoint-local DesignWare eDMA read channels
through vNTB. It keeps the export within pci-epf-vntb and ntb_hw_epf
rather than defining a generic remote-DMA ABI or using a separate PCI
DMA function.

On the endpoint, pci-epf-vntb reserves the complete eDMA read direction
and exposes those channels as a group. HDMA is not yet supported,
keeping the series minimal.

The DMA feature is opt-in through the pci-epf-vntb configfs attribute
'dma_bar', which is -1 by default. Without it, no DMA extension is
exported. pci-epf-ntb is unchanged.

Base and dependency
===================

This series is based on next-20260827 (3d83758432b5) plus:

  [PATCH v2 0/3] dmaengine: dw-edma: Prepare channels for remote use
  https://lore.kernel.org/r/20260828163611.2691264-1-den@valinux.co.jp/ (local)

The prerequisite is for the dmaengine tree and is not part of
pci/endpoint. linux-next provides a common buildable base for both
series. Once the prerequisite lands, this series can be rebased onto
pci/endpoint.

Best regards,
Koichiro
---
Changes in v3:
  - Rework DMA BAR setup around pci_epf_assign_bar_space() and submaps.
    Allocate backing only for uncovered BAR ranges. This handles the BAR
    backing alignment issue in pci-epf-vntb instead of adding a generic
    pci_epf_alloc_space() workaround. (Sashiko)
    https://lore.kernel.org/r/nvgnu3enktslxuiv7kdapcotoaxlfqhivar4jbf2tqvrk4otz5@exapzemrq37q/ (local)
  - Set up a shared DMA/MW BAR only once, preserve MW translations, and
    simplify error paths. (Sashiko)
  - Make dma_bar the explicit opt-in and drop use_dma and automatic BAR
    selection. Split BAR sharing into its own patch, then document the
    final interface at the end of the series instead of updating the
    documentation twice.
  - Validate peer-provided DW eDMA region offsets before MMIO mapping.
    (Sashiko)
  - Include several other minor cleanups and refactorings.

Changes in v2:
  - Rewrite most of v1 and move the dw-edma preparation into the
    companion series. Drop the generic pci-ep-dma API, auxiliary-bus
    child/frontend, test ntb client, and preparatory MW-state
    refactoring.
    See individual patch trailers for provenance.
  - Replace v1's post-registration channel-ID cache with driver-supplied
    static IDs. (Frank)
    https://lore.kernel.org/r/abMcgQOHDD55Yv0e@lizhi-Precision-Tower-5810/ (local)
  - Let pci-epf-vntb reserve channels with dma_request_channel() and
    configure interrupt routing with dmaengine_slave_config(). This
    removes the PCI EPC DMA delegation API. (Frank)
    https://lore.kernel.org/r/ao2nHoCwfTEEiFSr@SMW015318/ (local)
  - Drop v1's dma_offset and dma_num_chans attributes. use_dma now enables
    export of the complete eDMA read direction as a group.

v2: https://lore.kernel.org/r/20260828170932.2735807-1-den@valinux.co.jp/ (local)
v1: https://lore.kernel.org/r/20260312165005.1148676-1-den@valinux.co.jp/ (local)

Related PCI DMA EPF v7:
  https://lore.kernel.org/r/20260813063757.3131865-1-den@valinux.co.jp/ (local)


Koichiro Den (7):
  PCI: endpoint: Add DMA auxiliary resource metadata
  PCI: dwc: Expose endpoint DMA resources
  PCI: endpoint: pci-epf-vntb: Move epf_ntb_is_bar_used() up
  PCI: endpoint: pci-epf-vntb: Export endpoint DMA channels
  PCI: endpoint: pci-epf-vntb: Allow DMA and MW to share a BAR
  NTB: ntb_hw_epf: Discover vNTB-embedded DMA
  Documentation: PCI: endpoint: Document vNTB DMA export

 Documentation/PCI/endpoint/pci-vntb-howto.rst |  24 +-
 drivers/ntb/hw/epf/ntb_hw_epf.c               | 362 ++++++++-
 .../pci/controller/dwc/pcie-designware-ep.c   | 107 ++-
 drivers/pci/endpoint/functions/pci-epf-vntb.c | 716 ++++++++++++++++--
 include/linux/pci-epc.h                       |  34 +-
 5 files changed, 1166 insertions(+), 77 deletions(-)

-- 
2.51.0