From: swarren@wwwdotorg•org (Stephen Warren)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH V2] dma: tegra: register as an OF DMA controller
Date: Tue, 03 Dec 2013 10:52:09 -0700 [thread overview]
Message-ID: <529E1A49.6050808@wwwdotorg.org> (raw)
In-Reply-To: <201311292208.26215.arnd@arndb.de>
On 11/29/2013 02:08 PM, Arnd Bergmann wrote:
> On Monday 25 November 2013, Stephen Warren wrote:
>> Well, you suggested not using of_dma_simple_xlate() since it wasn't
>> appropriate. I then started to implement an open-coded xlate function,
>> but found that it was 99% identical to the same thing in the mmp driver,
>> and hence created a common of_dma_slave_xlate() so as not to just
>> cut/paste it everywhere. Unfortunately, I only sent that patch to
>> dmaengine at vger.kernel.org and the DMA maintainers, and there's no
>> archive of that list:-(
>
> Ok, I see. However, I think the need for nontrivial code to be duplicated
> across drivers is not a sign that we are missing a generic xlate function
> and another indirection level, but rather that we got the interface
> for dma_get_slave_channel() wrong (yes, that would be my fault).
>
> Can you try coming up with a different method to achieve the same
> where you use a different helper from the driver specific xlate
> function that does not require a callback?
>
> I think dma_get_slave_channel is great if you have one channel per
> request line and you can directly look up the channel from the
> DT data, but it is not good if you have pick a channel and work
> around the race.
Hmm. Can you take a look at "[PATCH V4] dma: add
dma_get_any_slave_channel(), for use in of_xlate()" at the link below.
It still implements this via xlate, but I don't see any benefit in
making drivers use a different API to request slave channels based on
how the DMA controller works.
http://lkml.org/lkml/2013/11/26/408
next prev parent reply other threads:[~2013-12-03 17:52 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-25 21:53 [PATCH V2] dma: tegra: register as an OF DMA controller Stephen Warren
2013-11-25 22:09 ` Arnd Bergmann
2013-11-25 22:30 ` Stephen Warren
2013-11-25 23:09 ` Dan Williams
2013-11-25 23:14 ` Stephen Warren
2013-11-26 1:13 ` Dan Williams
2013-11-29 21:08 ` Arnd Bergmann
2013-12-03 17:52 ` Stephen Warren [this message]
2013-12-04 1:22 ` Arnd Bergmann
2013-12-04 17:09 ` Stephen Warren
2013-12-04 17:18 ` Lars-Peter Clausen
2013-12-06 21:16 ` Dan Williams
2013-12-06 22:19 ` Arnd Bergmann
2013-11-29 14:17 ` Thierry Reding
2013-12-03 17:59 ` Stephen Warren
2013-12-04 8:29 ` Thierry Reding
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