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From: Chunyan Zhang <zhang.chunyan@linaro.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Kishon Vijay Abraham I <kishon@ti.com>,
	Ulf Hansson <ulf.hansson@linaro.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
	linux-mmc@vger.kernel.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Mark Brown <broonie@kernel.org>, Sekhar Nori <nsekhar@ti.com>,
	Lyra Zhang <zhang.lyra@gmail.com>
Subject: Re: [PATCH RFC 2/3] mmc: sdhci-omap: Add using external dma
Date: Wed, 7 Nov 2018 11:00:57 +0800	[thread overview]
Message-ID: <CAG2=9p-skR8xqqBrULS6_EWFX0H_mvvOJKDGVfzf026H_dychg@mail.gmail.com> (raw)
In-Reply-To: <CAK8P3a2X4tbx_R-5VgfApF-UPmJ_XuzH3hO_uVAfffC6h8WrJw@mail.gmail.com>

On Tue, 6 Nov 2018 at 20:51, Arnd Bergmann <arnd@arndb.de> wrote:
>
> On 11/5/18, Kishon Vijay Abraham I <kishon@ti.com> wrote:
> > On 05/11/18 8:46 AM, Chunyan Zhang wrote:
> >>
> >> +    sdhci_switch_extdma(host, true);
> >
> > A number of devices using sdhci-omap supports ADMA. So switching to
> > external
> > DMA shouldn't be unconditional.
> >
> > IMHO sdhci.c should see if the device supports ADMA or SDMA. If not it
> > should
> > try switching to external DMA and if external DMA too is not supported, it
> > should use PIO.
>
> What's the reasoning for preferring ADMA/SDMA over external DMA if
> both are supported?
>
> I'd expect that if the external DMA for some reason is worse than
> ADMA, we just wouldn't list it in the DT at all, but if it's listed and
> ADMA also works, then the driver should try to use it before falling
> back to ADMA.

Thanks Arnd and Kishon, let's see what Andrian and Ulf would suggest,
and then I will address in next version of patchset.

Thanks again,
Chunyan

>
>        Arnd

  reply	other threads:[~2018-11-07  3:01 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-05  3:16 [PATCH RFC 0/3] Add support for using external dma in SDHCI Chunyan Zhang
2018-11-05  3:16 ` [PATCH RFC 1/3] mmc: sdhci: add support for using external DMA devices Chunyan Zhang
2018-11-06 11:16   ` Arnd Bergmann
2018-11-07  2:56     ` Chunyan Zhang
2018-11-07 14:13   ` Adrian Hunter
2018-11-05  3:16 ` [PATCH RFC 2/3] mmc: sdhci-omap: Add using external dma Chunyan Zhang
2018-11-05  4:25   ` Kishon Vijay Abraham I
2018-11-06 12:51     ` Arnd Bergmann
2018-11-07  3:00       ` Chunyan Zhang [this message]
2018-11-09  5:27       ` Kishon Vijay Abraham I
2018-11-19 16:32         ` Ulf Hansson
2018-11-05  3:16 ` [PATCH RFC 3/3] dt-bindings: sdhci-omap: Add example for using dmaengine Chunyan Zhang

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