From: Mark Brown <broonie@kernel.org>
To: Andy Green <andy@warmcat.com>
Cc: John Stultz <john.stultz@linaro.org>,
zhangfei <zhangfei.gao@linaro.org>,
lkml <linux-kernel@vger.kernel.org>,
Jingoo Han <jg1.han@samsung.com>,
Krzysztof Kozlowski <k.kozlowski@samsung.com>,
Maxime Ripard <maxime.ripard@free-electrons.com>,
Vinod Koul <vinod.koul@intel.com>,
Dan Williams <dan.j.williams@intel.com>
Subject: Re: [PATCH 6/7] k3dma: Fix occasional DMA ERR issue by using proper dma api
Date: Thu, 21 Jul 2016 11:40:00 +0100 [thread overview]
Message-ID: <20160721104000.GM6509@sirena.org.uk> (raw)
In-Reply-To: <B261DC34-8E64-4B49-B826-B425799B94D9@warmcat.com>
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On Thu, Jul 21, 2016 at 02:27:02PM +0800, Andy Green wrote:
> On July 21, 2016 1:22:02 PM GMT+08:00, John Stultz <john.stultz@linaro.org> wrote:
> >On Wed, Jul 20, 2016 at 9:26 PM, zhangfei <zhangfei.gao@linaro.org>
Please fix your mail client to word wrap within paragraphs at something
substantially less than 80 columns. Doing this makes your messages much
easier to read and reply to.
> >> How about using wmb() flush before start dma to sync desc?
> >So I'm not going to pretend to be an expert here, but my understanding
> >is that wmb() syncrhonizes cpu write ordering operations across cpus,
> IIUI what the memory barrier does is tell the *compiler* to actually
> do any writes that the code asked for, but which otherwise might
> actually be deferred past that point. The compiler doesn't know that
> buffer area has other hardware snooping it, so by default it feels it
> can play tricks with what seems to it like just generally deferring
> spilling registers to memory. wmb makes sure the compiler's pending
> writes actually happen right there. (writel() etc definitions have
> one built-in, so they always do what you asked when you asked).
You might be interested in Mark Rutland's talk from ELC (Stale data, or
how we (mis-)manage modern caches):
http://events.linuxfoundation.org/sites/events/files/slides/slides_17.pdf
https://www.youtube.com/watch?v=F0SlIMHRnLk
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next prev parent reply other threads:[~2016-07-21 10:40 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-21 3:53 [PATCH 0/7 v3] K3DMA fixes for HiKey HDMI audio John Stultz
2016-07-21 3:53 ` [PATCH 1/7] k3dma: Fix hisi burst clipping John Stultz
2016-07-24 7:25 ` Vinod Koul
2016-07-29 22:40 ` John Stultz
2016-08-04 13:08 ` Vinod Koul
2016-08-04 17:36 ` John Stultz
2016-08-05 3:36 ` Vinod Koul
2016-07-21 3:53 ` [PATCH 2/7] k3dma: Fix dma err offsets John Stultz
2016-07-21 3:53 ` [PATCH 3/7] k3dma: Fix "nobody cared" message seen on any error John Stultz
2016-07-21 3:53 ` [PATCH 4/7] k3dma: Add cyclic mode for audio John Stultz
2016-07-24 7:31 ` Vinod Koul
2016-07-29 22:38 ` John Stultz
2016-07-21 3:53 ` [PATCH 5/7] k3dma: Fix memory handling with cyclic mode John Stultz
2016-07-21 3:53 ` [PATCH 6/7] k3dma: Fix occasional DMA ERR issue by using proper dma api John Stultz
2016-07-21 4:26 ` zhangfei
2016-07-21 5:22 ` John Stultz
2016-07-21 6:27 ` Andy Green
2016-07-21 10:40 ` Mark Brown [this message]
2016-07-21 13:12 ` Andy Green
2016-07-21 16:18 ` John Stultz
2016-07-21 19:57 ` Andy Green
2016-07-21 16:08 ` zhangfei
2016-07-21 3:53 ` [PATCH 7/7] Kconfig: Allow k3dma driver to be selected for more then HISI3xx platforms John Stultz
2016-07-22 6:56 ` kbuild test robot
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