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Message-ID: <29d03762-866a-4fdc-eddb-e24f6e631412@emlix.com>
Date: Mon, 16 Sep 2019 15:41:49 +0200
From: Philipp Puschmann <philipp.puschmann@...ix.com>
To: Robin Gong <yibin.gong@....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
Am 16.09.19 um 10:02 schrieb Robin Gong:
> 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
>
Hi Robin, yes i have reproduced the Bluetooth issue with my test case with kernel 4.15
and the newest 5.3.0-rc8-next-20190915. My test-case includes several custom-boards
communicating via Bluetooth with each other. I see the error within seconds to few minutes.
> 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
>
--
Philipp Puschmann, emlix GmbH, http://www.emlix.com
Fon +49 551 30664-0, Fax +49 551 30664-11
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