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From:   Robin Gong <yibin.gong@nxp.com>
To:     Philipp Puschmann <philipp.puschmann@emlix.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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Subject: RE: [PATCH 0/4] Fix UART DMA freezes for iMX6
Thread-Topic: [PATCH 0/4] Fix UART DMA freezes for iMX6
Thread-Index: AQHVaLAxu2UDdwNxk0eJG3Q3r0yNHKct9iKQ
Date:   Mon, 16 Sep 2019 08:02:49 +0000
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References: <20190911144943.21554-1-philipp.puschmann@emlix.com>
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On 2019/9/11 Philipp Puschmann <philipp.puschmann@emlix.com> wrote:
> For some years and since many kernel versions there are reports that RX
> UART DMA channel stops working at one point. So far the usual workaround
> was to disable RX DMA. This patches try to fix the underlying problem.
>=20
> When a running sdma script does not find any usable destination buffer to=
 put
> its data into it just leads to stopping the channel being scheduled again=
. As
> solution we we manually retrigger the sdma script for this channel and by=
 this
> dissolve the freeze.
>=20
> While this seems to work fine so far a further patch in this series incre=
ases the
> number of RX DMA periods for UART to reduce use cases running into such a
> situation.
>=20
> This patch series was tested with the current kernel and backported to ke=
rnel
> 4.15 with a special use case using a WL1837MOD via UART and provoking the
Hi Philipp, Could your Bluetooth issue be reproduce on latest linux-next? O=
r did
your kernel which can be reproduced include the below patch?

commit d1a792f3b4072bfac4150bb62aa34917b77fdb6d
Author: Russell King - ARM Linux <linux@arm.linux.org.uk>
Date:   Wed Jun 25 13:00:33 2014 +0100

    Update imx-sdma cyclic handling to report residue
> hanging of UART RX DMA within seconds after starting a test application.
> It resulted in well known
>   "Bluetooth: hci0: command 0x0408 tx timeout"
> errors and complete stop of UART data reception. Our Bluetooth traffic
> consists of many independent small packets, mostly only a few bytes, caus=
ing
> high usage of periods.
>=20
>=20
> Philipp Puschmann (4):
>   dmaengine: imx-sdma: fix buffer ownership
>   dmaengine: imx-sdma: fix dma freezes
>   serial: imx: adapt rx buffer and dma periods
>   dmaengine: imx-sdma: drop redundant variable
>=20
>  drivers/dma/imx-sdma.c   | 32 ++++++++++++++++++++++----------
>  drivers/tty/serial/imx.c |  5 ++---
>  2 files changed, 24 insertions(+), 13 deletions(-)
>=20
> --
> 2.23.0