Merge branch 'net-lan966x-add-support-for-pcie-fdma'

Daniel Machon says:

====================
net: lan966x: add support for PCIe FDMA

When lan966x operates as a PCIe endpoint, the driver currently uses
register-based I/O for frame injection and extraction. This approach is
functional but slow, topping out at around 33 Mbps on an Intel x86 host
with a lan966x PCIe card.

This series adds FDMA (Frame DMA) support for the PCIe path. When
operating as a PCIe endpoint, the internal FDMA engine on lan966x cannot
directly access host memory, so DMA buffers are allocated as contiguous
coherent memory and mapped through the PCIe Address Translation Unit
(ATU). The ATU provides outbound windows that translate internal FDMA
addresses to PCIe bus addresses, allowing the FDMA engine to read and
write host memory. Because the ATU requires contiguous address regions,
page_pool and normal per-page DMA mappings cannot be used. Instead,
frames are transferred using memcpy between the ATU-mapped buffers and
the network stack. With this, throughput increases from ~33 Mbps to
~620 Mbps for default MTU.

Patch 1 adds the shared drivers/net/ethernet/microchip/fdma/ directory
to the Sparx5 SoC MAINTAINERS entry.

Patches 2-4 prepare the shared FDMA library: patch 2 renames the
contiguous dataptr helpers for clarity, patch 3 adds PCIe ATU region
management and coherent DMA allocation with ATU mapping, and patch 4
gives the descriptor fields an explicit little-endian type, since on the
PCIe path the descriptors are written by the host CPU.

Patches 5-8 refactor the lan966x FDMA code to support both platform
and PCIe paths: extracting the LLP register write into a helper,
exporting shared functions, introducing a dedicated device for DMA
operations, and adding an ops dispatch table selected at probe time.

Patches 9-10 harden the existing FDMA path for the PCIe endpoint
lifecycle: patch 9 clears latched FDMA error/interrupt stickies after
the switch reset so they don't assert as soon as interrupts are
enabled, and patch 10 adds a shutdown() callback that quiesces the
FDMA engine on host warm reboot (on the PCIe card the FDMA survives
host reset and would otherwise keep the shared INTx asserted into
the next probe).

Patch 11 adds the core PCIe FDMA implementation with RX/TX using
contiguous ATU-mapped buffers. Patches 12 and 13 extend it with MTU
change and XDP support respectively. XDP_PASS, XDP_TX, XDP_DROP and
XDP_ABORTED are supported; XDP_REDIRECT is deliberately not, because
the PCIe data path does not use page_pool.

Patches 14-15 update the lan966x PCI device tree overlay to extend the
cpu register mapping to cover the ATU register space and add the FDMA
interrupt.

Patches 1-13 touch MAINTAINERS and drivers/net/ethernet/microchip/, and
are for the netdev tree.

Patches 14-15 touch drivers/misc/lan966x_pci.dtso, and are for the
char-misc tree.
====================

Link: https://patch.msgid.link/20260928-lan966x-pci-fdma-v9-0-a17caf60f89a@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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