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From: Frank Mori Hess <fmh6jj@gmail.com>
To: Vinod <vkoul@kernel.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>,
	dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org,
	Dan Williams <dan.j.williams@intel.com>,
	r.baldyga@hackerion.com, Krzysztof Kozlowski <krzk@kernel.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	Linux Samsung SOC <linux-samsung-soc@vger.kernel.org>
Subject: Re: Revert "dmaengine: pl330: add DMA_PAUSE feature"
Date: Tue, 15 May 2018 11:50:46 -0400	[thread overview]
Message-ID: <CAJz5Open++Dj=a4ty-JbnZBFoqbMQKU6qYumJKSRMRLp_3erSw@mail.gmail.com> (raw)
In-Reply-To: <20180515062144.GC13271@vkoul-mobl>

On Tue, May 15, 2018 at 2:21 AM, Vinod <vkoul@kernel.org> wrote:
>
> For Pause/resume data loss is _not_ expected.
>
>> > and some of the 8250 drivers like 8250_dw.c set a maxburst > 1.  If it
>> > can't count on the pause/residue/terminate working without data loss
>> > then it is just broken.  As is the 8250_omap.c driver.  Is the
>> > description of dmaengine_pause in the documentation of "This pauses
>> > activity on the DMA channel without data loss" to be interpreted as
>> > "as long as you resume afterwards"?
>>
>> I assume that this requirement is for both - resuming and terminating.
>
> Terminate is abort, data loss may happen here.

Wait, are you saying if you do

dma pause
read residue
dma terminate

then it is acceptable for there to be data loss, because it can be
blamed on the terminate?  In that case the usage of dmaengine in all
the 8250 serial drivers is broken.  Every time there is a break in the
incoming rx data, the 8250 driver does pause/residue/terminate which
could potentially cause data from the incoming data stream to be
dropped.

  parent reply	other threads:[~2018-05-15 15:52 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-28 21:50 [PATCH] Revert "dmaengine: pl330: add DMA_PAUSE feature" Frank Mori Hess
2018-05-02  4:32 ` Vinod Koul
2018-05-02 14:37   ` Frank Mori Hess
2018-05-03  9:01     ` Vinod Koul
2018-05-03 16:35 ` Vinod Koul
     [not found] ` <CGME20180508090407eucas1p13713284c2d3f5aa5c66f8d136be683c1@eucas1p1.samsung.com>
2018-05-08  9:04   ` Marek Szyprowski
2018-05-08 14:36     ` Frank Mori Hess
2018-05-09  6:59       ` Vinod Koul
2018-05-09 13:19       ` Marek Szyprowski
2018-05-09 17:48         ` Frank Mori Hess
2018-05-10  8:31           ` Marek Szyprowski
2018-05-10 16:04             ` Frank Mori Hess
2018-05-11 12:57               ` Marek Szyprowski
2018-05-11 15:57                 ` Frank Mori Hess
2018-05-15  6:21                 ` Vinod
2018-05-15 12:24                   ` Marek Szyprowski
2018-05-15 13:45                     ` Vinod
2018-05-15 15:50                   ` Frank Mori Hess [this message]
2018-05-17  4:19                     ` Vinod Koul
2018-05-17 16:20                       ` Frank Mori Hess
2018-05-17 17:22                         ` Lars-Peter Clausen
2018-05-18 19:01                           ` Frank Mori Hess
2018-05-18  4:03                         ` Vinod
2018-05-18  6:28                           ` Marek Szyprowski
2018-05-18  7:21                             ` Vinod
2018-05-29  5:17                               ` Marek Szyprowski
2018-05-29  7:09                                 ` Vinod
2018-05-18 18:56                           ` Frank Mori Hess
2018-05-21  9:16                             ` Vinod Koul
2018-05-22  0:56                               ` Frank Mori Hess
2018-05-22  3:37                                 ` Vinod Koul
2018-05-22 14:27                                   ` Frank Mori Hess
2018-05-23  5:39                                     ` Vinod

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