Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
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
Thread-Topic: [EXT] [PATCH v4 0/3] Fix UART DMA freezes for i.MX SOCs
Thread-Index: AQHVbvawZ3M9Pccxp0iKGAqRTaAJlKcz3AJg
Date:   Fri, 20 Sep 2019 02:44:33 +0000
Message-ID: <VI1PR0402MB36002C1C1E5A48EBA2385406FF880@VI1PR0402MB3600.eurprd04.prod.outlook.com>
References: <20190919142942.12469-1-philipp.puschmann@emlix.com>
In-Reply-To: <20190919142942.12469-1-philipp.puschmann@emlix.com>
Accept-Language: zh-CN, en-US
Content-Language: en-US
received-spf: None (protection.outlook.com: nxp.com does not designate
 permitted sender hosts)
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-Network-Message-Id: e38708cf-f9b0-45be-5cab-08d73d74782b
X-MS-Exchange-CrossTenant-originalarrivaltime: 20 Sep 2019 02:44:33.6223
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: 686ea1d3-bc2b-4c6f-a92c-d99c5c301635
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: LUx0JS+3ci5cSWOyo7OWhbaapN5XMf5UmKSc8MlMP0kP68pAyrFk5jTpQjnB+bPXgU5NhNDG5bVuUEduoHzW0Q==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR0402MB3712
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

From: Philipp Puschmann <philipp.puschmann@emlix.com> Sent: Thursday, Septe=
mber 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.
>=20
> 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 th=
is
> dissolve the freeze.
>=20
> 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.
>=20
> This patch series was tested with the current kernel and backported to ke=
rnel
> 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, caus=
ing
> high usage of periods.
>=20
> Changelog v4:
>  - fixed the fixes tags
>=20
> Changelog v3:
>  - fixes typo in dma_wmb
>  - add fixes tags
>=20
> 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"
>=20
> Philipp Puschmann (3):
>   dmaengine: imx-sdma: fix buffer ownership
>   dmaengine: imx-sdma: fix dma freezes
>   dmaengine: imx-sdma: drop redundant variable
>=20
>  drivers/dma/imx-sdma.c | 32 ++++++++++++++++++++++----------
>  1 file changed, 22 insertions(+), 10 deletions(-)
>=20
> --
> 2.23.0

The patch set look fine that is really to fix some corner issue from the lo=
gical view.

Reviewed-by: Fugang Duan <fugang.duan@nxp.com>