From: Andy Duan <fugang.duan@nxp.com>
To: Philipp Puschmann <philipp.puschmann@emlix.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: Robin Gong <yibin.gong@nxp.com>,
"l.stach@pengutronix.de" <l.stach@pengutronix.de>,
"dan.j.williams@intel.com" <dan.j.williams@intel.com>,
"vkoul@kernel.org" <vkoul@kernel.org>,
"shawnguo@kernel.org" <shawnguo@kernel.org>,
"s.hauer@pengutronix.de" <s.hauer@pengutronix.de>,
"kernel@pengutronix.de" <kernel@pengutronix.de>,
"festevam@gmail.com" <festevam@gmail.com>,
dl-linux-imx <linux-imx@nxp.com>,
"dmaengine@vger.kernel.or" <dmaengine@vger.kernel.or>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: RE: [EXT] [PATCH v4 0/3] Fix UART DMA freezes for i.MX SOCs
Date: Fri, 20 Sep 2019 02:44:33 +0000 [thread overview]
Message-ID: <VI1PR0402MB36002C1C1E5A48EBA2385406FF880@VI1PR0402MB3600.eurprd04.prod.outlook.com> (raw)
In-Reply-To: <20190919142942.12469-1-philipp.puschmann@emlix.com>
From: Philipp Puschmann <philipp.puschmann@emlix.com> Sent: Thursday, September 19, 2019 10:30 PM
> 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 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 manually retrigger the sdma script for this channel and by this
> dissolve the freeze.
>
> While this seems to work fine so far, it may come to buffer overruns when the
> channel - even temporary - is stopped. This case has to be addressed by
> device drivers by increasing the number of DMA periods.
>
> 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.
>
> Changelog v4:
> - fixed the fixes tags
>
> Changelog v3:
> - fixes typo in dma_wmb
> - add fixes tags
>
> Changelog v2:
> - adapt title (this patches are not only for i.MX6)
> - improve some comments and patch descriptions
> - add a dma_wb() around BD_DONE flag
> - add Reviewed-by tags
> - split off "serial: imx: adapt rx buffer and dma periods"
>
> Philipp Puschmann (3):
> dmaengine: imx-sdma: fix buffer ownership
> dmaengine: imx-sdma: fix dma freezes
> dmaengine: imx-sdma: drop redundant variable
>
> drivers/dma/imx-sdma.c | 32 ++++++++++++++++++++++----------
> 1 file changed, 22 insertions(+), 10 deletions(-)
>
> --
> 2.23.0
The patch set look fine that is really to fix some corner issue from the logical view.
Reviewed-by: Fugang Duan <fugang.duan@nxp.com>
prev parent reply other threads:[~2019-09-20 2:44 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-19 14:29 [PATCH v4 0/3] Fix UART DMA freezes for i.MX SOCs Philipp Puschmann
2019-09-19 14:29 ` [PATCH v4 1/3] dmaengine: imx-sdma: fix buffer ownership Philipp Puschmann
2019-09-19 14:29 ` [PATCH v4 2/3] dmaengine: imx-sdma: fix dma freezes Philipp Puschmann
2019-09-19 15:19 ` Jan Lübbe
2019-09-20 8:53 ` Philipp Puschmann
2019-09-20 9:26 ` Lucas Stach
2019-09-24 1:38 ` Robin Gong
2019-09-19 14:29 ` [PATCH v4 3/3] dmaengine: imx-sdma: drop redundant variable Philipp Puschmann
2019-09-20 2:44 ` Andy Duan [this message]
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