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Message-ID: <2613a28d-d363-ee4e-679a-e7442e6fde48@emlix.com>
Date: Mon, 16 Sep 2019 15:55:04 +0200
From: Philipp Puschmann <philipp.puschmann@...ix.com>
To: Fabio Estevam <festevam@...il.com>,
Robin Gong <yibin.gong@....com>,
Fugang Duan <fugang.duan@....com>
Cc: linux-kernel <linux-kernel@...r.kernel.org>,
Vinod <vkoul@...nel.org>,
Dan Williams <dan.j.williams@...el.com>,
Shawn Guo <shawnguo@...nel.org>,
Sascha Hauer <kernel@...gutronix.de>,
NXP Linux Team <linux-imx@....com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jiri Slaby <jslaby@...e.com>, dmaengine@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH 0/4] Fix UART DMA freezes for iMX6
Hi Fabio,
Am 12.09.19 um 20:23 schrieb Fabio Estevam:
> Hi Philipp,
>
> Thanks for submitting these fixes.
>
> On Wed, Sep 11, 2019 at 11:50 AM 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 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
>
> I have some suggestions:
>
> 1. Please split this in two series: one for dmaengine and other one for serial
>
> 2. Please add Fixes tag when appropriate, so that the fixes can be
> backported to stable kernels.
>
> 3. Please Cc Robin and Andy
>
> Thanks
>
Thanks for the hints. I will apply them if the contentual feedback is positive.
p.s. Did you forget to add Andy? I don't see a Andy in the to- and cc-list.
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