net: lan966x: add FDMA LLP register write helper

The FDMA Link List Pointer (LLP) register points to the first DCB in the
chain and must be written before the channel is activated. This tells
the FDMA engine where to begin DMA transfers.

Move the LLP register writes from the channel start/activate functions
into the allocation functions and introduce a shared
lan966x_fdma_llp_configure() helper. This is needed because the upcoming
PCIe FDMA path writes ATU-translated addresses to the LLP registers
instead of DMA addresses. Keeping the writes in the shared
start/activate path would overwrite these translated addresses.

Tested-by: Herve Codina <herve.codina@bootlin.com>
Signed-off-by: Daniel Machon <daniel.machon@microchip.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260928-lan966x-pci-fdma-v9-5-a17caf60f89a@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions