From: Vinod Koul <vinod.koul@intel.com>
To: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Cc: linux-kernel@vger.kernel.org,
"'Jassi Brar'" <jassisinghbrar@gmail.com>,
Linus Walleij <linus.walleij@linaro.org>,
rmk <rmk@arm.linux.org.uk>
Subject: Re: [PATCH/RFC] dmaengine: add a slave parameter to __dma_request_channel()
Date: Wed, 07 Mar 2012 11:58:07 +0530 [thread overview]
Message-ID: <1331101687.24656.319.camel@vkoul-udesk3> (raw)
In-Reply-To: <Pine.LNX.4.64.1203061339330.9300@axis700.grange>
On Tue, 2012-03-06 at 14:03 +0100, Guennadi Liakhovetski wrote:
<adding few folks to thread, who i may be intrested in this discussion>
> But the DMAC is certainly a better match for making channel-selection
> decisions.
I am not sure about that as well...
>
> > Bigger question is who knows about this mapping and how do we
> > incorporate this mapping into channel allocation
>
> The platform does. And this knowledge has to be passed to the relevant
> driver. But I think it's the DMAC driver, that is relevant, not the client
> driver. The platform would supply information like
>
> DMAC #1
> channel #1
> (can be used for) device #1
> device #2
> ...
> channel #2
> ...
> ...
right :-)
and we need to ensure that somehow this information is presented to
dmaengine and dmaengine uses this information to filter the channel
requests. In past we had good discussion [1], [2], [3] on this topic but
unfortunately nothing came out of it.
I like the approach outlined by Linus W [1], where we can get the
information from platform (DT, FW,....) and its presented to dmaengine.
I think we need to solve this _now_. There are two aspects
a) to ensure dmaengine understand channel-client mapping. For this we
can start with idea in [1] and see if this suits everyones needs
b) how to ensure the platform gives this information in variety of arch
we have (arm, x86, sh-....)
Thoughts...?
> And I don't think, it would be reasonable to let every slave driver use
> this information. These lists can also be optimised for specific
> platforms. E.g., on some sh-mobile SoCs you have two DMAC types. One of
> them can serve devices from list A on any channel, the other one - from
> list B. So, all you have to do, is to reference either A or B from your
> DMAC platform data. Whereas doing a reverse mapping: for each (potential)
> DMA user reference a list of channels, that it can use - would be really
> clumsy.
>
[1]:
http://lists.infradead.org/pipermail/linux-arm-kernel/2011-August/060717.html
[2]:
http://lists.infradead.org/pipermail/linux-arm-kernel/2011-July/059212.html
[3]:
http://lists.infradead.org/pipermail/linux-arm-kernel/2011-July/059217.html
--
~Vinod
next prev parent reply other threads:[~2012-03-07 6:23 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-01 15:26 [PATCH/RFC] dmaengine: add a slave parameter to __dma_request_channel() Guennadi Liakhovetski
2012-03-02 13:21 ` Guennadi Liakhovetski
2012-03-06 8:30 ` Vinod Koul
2012-03-06 8:53 ` Guennadi Liakhovetski
2012-03-06 12:08 ` Vinod Koul
2012-03-06 13:03 ` Guennadi Liakhovetski
2012-03-07 6:28 ` Vinod Koul [this message]
2012-03-07 9:18 ` Guennadi Liakhovetski
2012-03-07 9:30 ` Russell King - ARM Linux
2012-03-07 9:55 ` Linus Walleij
2012-03-07 10:02 ` Guennadi Liakhovetski
2012-03-07 10:31 ` Russell King - ARM Linux
2012-03-07 12:30 ` Guennadi Liakhovetski
2012-03-07 12:45 ` Guennadi Liakhovetski
2012-03-07 12:46 ` Russell King - ARM Linux
2012-03-07 13:49 ` Guennadi Liakhovetski
2012-03-07 14:26 ` Russell King - ARM Linux
2012-03-07 15:44 ` Guennadi Liakhovetski
2012-03-07 16:27 ` Russell King - ARM Linux
2012-03-07 18:21 ` Guennadi Liakhovetski
2012-03-08 6:30 ` Vinod Koul
2012-03-08 10:16 ` Guennadi Liakhovetski
2012-03-08 10:55 ` Vinod Koul
2012-03-08 11:22 ` Guennadi Liakhovetski
2012-03-08 11:34 ` Vinod Koul
2012-03-08 12:58 ` Vinod Koul
2012-03-08 13:18 ` Guennadi Liakhovetski
2012-03-09 9:21 ` Vinod Koul
2012-03-09 9:24 ` Guennadi Liakhovetski
2012-03-09 9:39 ` Vinod Koul
2012-03-09 12:20 ` Guennadi Liakhovetski
2012-03-09 14:07 ` Russell King - ARM Linux
2012-03-09 14:15 ` Guennadi Liakhovetski
2012-03-12 2:47 ` Vinod Koul
2012-03-12 19:47 ` Linus Walleij
2012-03-16 9:36 ` Guennadi Liakhovetski
2012-03-16 10:16 ` Linus Walleij
2012-03-16 10:31 ` Russell King - ARM Linux
2012-03-16 11:09 ` Guennadi Liakhovetski
2012-03-16 14:11 ` Linus Walleij
2012-03-16 14:28 ` Guennadi Liakhovetski
2012-03-30 5:44 ` Linus Walleij
2012-03-30 6:40 ` Guennadi Liakhovetski
2012-03-30 10:38 ` Russell King - ARM Linux
2012-04-03 20:36 ` Linus Walleij
2012-04-03 20:44 ` Linus Walleij
2012-04-12 21:33 ` Guennadi Liakhovetski
2012-04-12 23:48 ` Russell King - ARM Linux
2012-03-30 10:29 ` Russell King - ARM Linux
2012-03-30 10:40 ` Guennadi Liakhovetski
2012-03-30 10:43 ` Russell King - ARM Linux
2012-03-19 11:58 ` Vinod Koul
2012-03-30 10:25 ` Russell King - ARM Linux
2012-03-19 11:39 ` Vinod Koul
2012-03-19 11:37 ` Vinod Koul
2012-03-19 11:47 ` Guennadi Liakhovetski
2012-03-19 13:34 ` Vinod Koul
2012-03-19 13:38 ` Guennadi Liakhovetski
2012-03-19 14:00 ` Vinod Koul
2012-03-19 14:09 ` Guennadi Liakhovetski
2012-03-19 14:22 ` Vinod Koul
2012-03-19 14:45 ` Guennadi Liakhovetski
2012-03-19 16:20 ` Vinod Koul
2012-03-19 16:32 ` Guennadi Liakhovetski
2012-03-20 7:11 ` Vinod Koul
2012-03-08 11:46 ` Linus Walleij
2012-03-08 12:36 ` Guennadi Liakhovetski
2012-03-07 16:31 ` Linus Walleij
2012-03-07 16:20 ` Linus Walleij
2012-03-07 9:46 ` Linus Walleij
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