dmaengine: dw-edma: Add partial channel ownership mode

Browse source

A DesignWare eDMA instance may represent only a subset of channels that
is also initialized by another OS instance, such as an endpoint-side OS.
Add a partial ownership flag for instances that must preserve
controller-wide state owned by that peer.

In partial ownership mode, dw-edma skips the initial core reset and uses
the limited quiesce path in probe() and remove() instead of the full
core-off path. The flag also makes the driver validate the ownership
granularity required by each register layout before registering
channels.

Probe fails if the limited quiesce cannot stop its resources; remove
reports the error after completing the remaining driver teardown.

Partial instances also skip interrupt-emulation doorbell allocation: the
emulated doorbell is a controller-level resource, and a partial owner
must not claim it on behalf of the whole block.

For EDMA_MF_EDMA_UNROLL and EDMA_MF_HDMA_COMPAT, the driver programs
per-direction registers, such as DMA_{WRITE,READ}_INT_MASK_OFF and
DMA_{WRITE,READ}_INT_CLEAR_OFF. These register layouts have at most
EDMA_MAX_{WR,RD}_CH channels per direction, so the capped hardware
channel count still represents the whole direction. A partial instance
can therefore expose write or read channels only if it owns every
channel in that direction; otherwise two OS instances could update the
same direction-wide registers without a shared locking protocol.

In contrast, HDMA native uses per-channel registers, so it can be owned
at channel granularity.

Signed-off-by: Koichiro Den <den@valinux.co.jp>
Link: https://patch.msgid.link/20260721062815.4117887-6-den@valinux.co.jp
Signed-off-by: Vinod Koul <vkoul@kernel.org>

...

This commit is contained in:

Koichiro Den 2026-07-21 15:28:06 +09:00 • committed by Vinod Koul

parent 647217abea

commit b24a5e9db6

2 changed files with 76 additions and 12 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

81

drivers/dma/dw-edma/dw-edma-core.c

View file

7

include/linux/dma/edma.h

View file