linux-kernel - RE: [PATCH 0/4] Fix UART DMA freezes for iMX6

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Message-ID: <VE1PR04MB66383FAB08506993B305AC8D898C0@VE1PR04MB6638.eurprd04.prod.outlook.com>
Date:   Mon, 16 Sep 2019 08:02:49 +0000
From:   Robin Gong <yibin.gong@....com>
To:     Philipp Puschmann <philipp.puschmann@...ix.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "vkoul@...nel.org" <vkoul@...nel.org>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        dl-linux-imx <linux-imx@....com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "jslaby@...e.com" <jslaby@...e.com>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>
Subject: RE: [PATCH 0/4] Fix UART DMA freezes for iMX6

On 2019/9/11 Philipp Puschmann <philipp.puschmann@...ix.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.
> 
> 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@....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, 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