Message-ID: <sashiko-outbox-206214@kernel.org>
From: sashiko-bot@kernel.org
Subject: Re: [PATCH v11 8/8] serial: 8250: retain DMA resources when
 termination fails
Reply-To: sashiko-reviews@lists.linux.dev
To: "James Hilliard" <james.hilliard1@gmail.com>
Cc: linux-serial@vger.kernel.org
In-Reply-To: <20261109-submit-serial-8250-dma-cancel-v1-v11-8-6364edca63d6@gmail.com>
References: <20261109-submit-serial-8250-dma-cancel-v1-v11-0-6364edca63d6@gmail.com>
 <20261109-submit-serial-8250-dma-cancel-v1-v11-8-6364edca63d6@gmail.com>
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Date: Tue, 10 Nov 2026 04:35:32 +0000
Precedence: list

> serial8250_release_dma() ignores the return from dmaengine_terminate_sync=
()
> before freeing the coherent RX buffer, unmapping the TX FIFO and releasing
> the channels. If the provider fails to stop a channel, the DMAengine
> wrapper returns the error without synchronizing its callbacks. Hardware
> or a detached callback can then access the released storage and state.
>=20
> Checking the error and returning early would not preserve their lifetime:
> serial core frees the TX FIFO after the driver's shutdown callback return=
s,
> and port removal can then release the callback context as well.
>=20
> Require successful synchronous termination of both channels before
> releasing any DMA resources. Retry failed channels after a sleep outside
> the port lock, leaving channels that have already stopped and drained
> alone. Keep the shutdown gate and storage reservation in place throughout
> the retries.
>=20
> Start retries with a 1 ms sleep and double it up to one second. This
> makes short-lived failures responsive while bounding sustained retry
> activity; neither delay is a hardware timeout. Report the initial failure
> and ongoing failures with the elapsed time and current RX/TX error codes.
> Track the five-second progress-report interval separately for each
> teardown, so failures on different ports are reported independently.
> Report recovery once both channels have stopped and drained.
>=20
> A permanently failed DMA engine blocks close or removal. This deliberately
> retains the buffers, mappings, channels and callback context until the
> provider can establish that they are no longer in use.
>=20
> Fixes: 9ee4b83e51f7 ("serial: 8250: Add support for dmaengine")
> Signed-off-by: James Hilliard <james.hilliard1@gmail.com>

Sashiko has reviewed this patch and found no issues.

--=20
Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261109-submit-ser=
ial-8250-dma-cancel-v1-v11-0-6364edca63d6@gmail.com?part=3D8