On 2019/9/11 Philipp Puschmann <philipp.puschmann@xxxxxxxxx> 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.
>
> 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.
>
> While this seems to work fine so far a further patch in this series increases the
> number of RX DMA periods for UART to reduce use cases running into such a
> situation.
>
> This patch series was tested with the current kernel and backported to kernel
> 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? Or did
your kernel which can be reproduced include the below patch?
commit d1a792f3b4072bfac4150bb62aa34917b77fdb6d
Author: Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx>
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, causing
> high usage of periods.
>
>
> 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
>
> drivers/dma/imx-sdma.c | 32 ++++++++++++++++++++++----------
> drivers/tty/serial/imx.c | 5 ++---
> 2 files changed, 24 insertions(+), 13 deletions(-)
>
> --
> 2.23.0
