From: "Łukasz Czerwiński" <l.czerwinski@samsung.com>
To: Mark Brown <broonie@kernel.org>
Cc: s.nawrocki@samsung.com, linux-samsung-soc@vger.kernel.org,
linux-spi@vger.kernel.org
Subject: Re: [RFC PATCH 6/6] spi: spi-s3c64xx: Move DMA initialization
Date: Tue, 10 Sep 2013 13:24:01 +0200 [thread overview]
Message-ID: <522F0151.50905@samsung.com> (raw)
In-Reply-To: <20130909145351.GD29403@sirena.org.uk>
On 09/09/2013 04:53 PM, Mark Brown wrote:
> On Mon, Sep 09, 2013 at 04:09:26PM +0200, Lukasz Czerwinski wrote:
>> This patch removes DMA channel initialization and deinitialization for each
>> transfer. Now DMA channel is requested only at the driver initialization
>> and stored in driver data.
>
> So, this is fine but I had been under the impression that one of the
> reasons that the channels were only being requested at transfer time was
> that they could be used for other purposes too. If that is not the case
> then fine, if that is the case then probably moving to prepare/unprepare
> transfer hardware (when the clocks are enabled) would make more sense -
> that'd avoid repeated allocations and frees while the controller is busy
> which should be the main issue performance wise.
>
For 16kB buffer upload time is reduced from ~90ms to ~80ms (I tested
with S5C73M3 355560B transfer). If you think that performance increase
isn't valuable we should skip that patch.
amba-pl80 uses virtual DMA channels support so driver won't occupy all
the time physical channel. pl330 driver don't use such framework but It
will be very hard to occupy all channels at the same time. If I'm wrong
please correct me.
Thanks
Lukasz
next prev parent reply other threads:[~2013-09-10 11:24 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-09 14:09 [RFC PATCH 0/6] spi/s3c64xx: clean up and optimization Lukasz Czerwinski
2013-09-09 14:09 ` [RFC PATCH 1/6] spi: spi-s3c64xx: Remove platform dependent code Lukasz Czerwinski
2013-09-09 14:38 ` Mark Brown
2013-09-11 16:21 ` Heiko Stübner
2013-09-09 14:09 ` [RFC PATCH 2/6] spi: spi-s3c64xx: Correct functions namespacing Lukasz Czerwinski
2013-09-09 14:09 ` [RFC PATCH 3/6] spi: spi-s3c64xx: Add coherent buffers for DMA transfers Lukasz Czerwinski
2013-09-09 14:45 ` Mark Brown
2013-09-10 11:23 ` Łukasz Czerwiński
2013-09-10 12:02 ` Mark Brown
2013-09-11 7:48 ` Łukasz Czerwiński
2013-09-09 14:09 ` [RFC PATCH 4/6] spi: spi-s3c64xx: Remove redundant code Lukasz Czerwinski
2013-09-09 14:09 ` [RFC PATCH 5/6] spi: spi-s3c64xx: Use module_platform_driver() Lukasz Czerwinski
2013-09-09 14:47 ` Mark Brown
2013-09-09 14:09 ` [RFC PATCH 6/6] spi: spi-s3c64xx: Move DMA initialization Lukasz Czerwinski
2013-09-09 14:53 ` Mark Brown
2013-09-10 11:24 ` Łukasz Czerwiński [this message]
2013-09-10 12:03 ` Mark Brown
2013-09-10 13:16 ` Łukasz Czerwiński
2013-09-10 16:32 ` Mark Brown
2013-09-11 7:45 ` Łukasz Czerwiński
2013-09-11 10:03 ` Mark Brown
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