Re: [PATCH v2 3/6] dmaengine: sun6i: serialize channel reassignment with interrupt handling

[Frank Li]

On Fri, Oct 23, 2026 at 12:42:37PM -0600, James Hilliard wrote:
> The allocator changes vchan->phy and pchan->vchan under sdev->lock, but
> termination reads the physical channel before taking either lock. The IRQ
> handler also takes an owner snapshot without protecting it. Termination
> can therefore miss a new assignment or detach an owner while an interrupt
> is about to complete its descriptor. An IRQ status snapshot can survive
> reassignment and be applied to the next transfer.
>
> Use sdev->lock for physical-channel ownership, pending channels and the
> shared interrupt registers, nesting vc.lock inside it for descriptor
> lists and cookie updates. Allocate and start each pending channel in one
> critical section. Read and acknowledge IRQ status under the same outer
> lock, and protect cyclic notifications as well as ordinary completions.
>
> Clear the active descriptor pointer before publishing finite completion
> to virt-dma, whose tasklet may free it independently of the allocator.
> An assigned channel without an active descriptor is ready for the
> allocator to start its next transfer or release it. This replaces the
> completed-descriptor pointer and keeps residue queries and termination
> from consulting a descriptor already handed to virt-dma.
>
> Mask and clear a stopped channel's IRQs before releasing its ownership,
> and clear pending status before starting a new descriptor. Schedule the
> allocator after termination so other pending channels can use the released
> physical channel without depending on another device interrupt.
>
> This also keeps process-context acquisitions IRQ-safe. Client callbacks
> remain outside these locks in the virtual-channel completion tasklet.
>
> Fixes: 555859308723 ("dmaengine: sun6i: Add driver for the Allwinner A31 DMA controller")
> Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
> Closes: https://lore.kernel.org/r/20260706065650.34B131F00A3A@xxxxxxxxxxxxxxx
> Signed-off-by: James Hilliard <james.hilliard1@xxxxxxxxx>
> ---

Is it possible split to more small change? And you almost add sdev->lock,
any place only use vc.lock without sdev->lock?

Frank