net: mana: Fall back to scattered pages for GDMA queues

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Each GDMA queue ring is one dma_alloc_coherent() of the whole ring size.
Such high-order allocations fail first under memory fragmentation, so
queue setup can fail with memory still free.

The hardware does not need the ring physically contiguous:
mana_gd_create_dma_region() already maps it as a list of MANA_PAGE_SIZE
(4K) device addresses. Only the driver's linear CPU view needs
contiguity, and it goes through mana_gd_ring_ptr() and
mana_gd_ring_contig_avail(); change both to map offsets onto
scattered pages.

Add a fallback in mana_gd_alloc_memory(): data-path queues pass
allow_scatter=true, so when the contiguous allocation fails the ring is
backed by a vector of scattered PAGE_SIZE (order-0) coherent pages,
presenting the same DMA page-list layout to the device. The HW channel
bootstrap keeps allow_scatter=false, and the debugfs ring dumper reads
scattered rings through the same helpers.

Signed-off-by: Aditya Garg <gargaditya@linux.microsoft.com>
Link: https://patch.msgid.link/20260807210002.1695263-3-gargaditya@linux.microsoft.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

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This commit is contained in:

Aditya Garg 2026-08-07 13:56:36 -07:00 • committed by Paolo Abeni

parent 1da1a037bc

commit 23adfc77c2

4 changed files with 168 additions and 16 deletions

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160

drivers/net/ethernet/microsoft/mana/gdma_main.c

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2

drivers/net/ethernet/microsoft/mana/hw_channel.c

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3

drivers/net/ethernet/microsoft/mana/mana_en.c

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19

include/net/mana/gdma.h

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