From: Vinod <vkoul@kernel.org>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>,
Mark Brown <broonie@kernel.org>,
Lars-Peter Clausen <lars@metafoo.de>,
dmaengine <dmaengine@vger.kernel.org>,
ALSA Development Mailing List <alsa-devel@alsa-project.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Dan Williams <dan.j.williams@intel.com>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Subject: Re: [PATCH] dma: add support for reporting pause and resume separately
Date: Fri, 6 Jul 2018 11:30:36 +0530 [thread overview]
Message-ID: <20180706060036.GR22377@vkoul-mobl> (raw)
In-Reply-To: <CAHp75Vfy8=i3dSYoQ5Uto-RtmU6E8BVWU1dmG8BihN=Wtkr+_A@mail.gmail.com>
On 04-07-18, 13:38, Andy Shevchenko wrote:
> On Wed, Jul 4, 2018 at 10:00 AM, Vinod <vkoul@kernel.org> wrote:
> > Hi Marek,
> >
> > On 02-07-18, 15:08, Marek Szyprowski wrote:
> >> 'cmd_pause' DMA channel capability means that respective DMA engine
> >> supports both pausing and resuming given DMA channel. However, in some
> >> cases it is important to know if DMA channel can be paused without the
> >> need to resume it. This is a typical requirement for proper residue
> >> reading on transfer timeout in UART drivers. There are also some DMA
> >> engines with limited hardware, which doesn't really support resuming.
> >
> > Am curious given that your hardware does not support resume, what was motivation
> > for adding pause?
> >
> >> Reporting pause and resume capabilities separately allows UART drivers to
> >> properly check for the really required capabilities and operate in DMA
> >> mode also in systems with limited DMA hardware. On the other hand drivers,
> >> which rely on full channel suspend/resume support, should now check for
> >> both 'pause' and 'resume' features.
> >>
> >> Existing clients of dma_get_slave_caps() have been checked and the only
> >> driver which rely on proper channel resuming is soc-generic-dmaengine-pcm
> >> driver, which has been updated to check the newly added capability.
> >> Existing 'cmd_pause' now only indicates that DMA engine support pausing
> >> given DMA channel.
> >
> > The change looks fine to me. I was hoping that serial would also check
> > this..
>
> AFAIU serial does not need to resume.
I meant the serial should check for Pause capability..
--
~Vinod
next prev parent reply other threads:[~2018-07-06 6:00 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20180702130819eucas1p2e11d8fabec93ba78d9e84f4ca6e5fd65@eucas1p2.samsung.com>
2018-07-02 13:08 ` [PATCH] dma: add support for reporting pause and resume separately Marek Szyprowski
2018-07-04 7:00 ` Vinod
2018-07-04 10:38 ` Andy Shevchenko
2018-07-06 6:00 ` Vinod [this message]
2018-07-06 6:22 ` Marek Szyprowski
2018-07-09 11:17 ` Mark Brown
2018-07-09 17:29 ` Vinod
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