From: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>,
Vinod Koul <vinod.koul@intel.com>,
linux-kernel@vger.kernel.org,
Jassi Brar <jassisinghbrar@gmail.com>,
Magnus Damm <magnus.damm@gmail.com>,
Paul Mundt <lethal@linux-sh.org>
Subject: Re: [PATCH/RFC] dmaengine: add a slave parameter to __dma_request_channel()
Date: Thu, 12 Apr 2012 23:33:28 +0200 (CEST) [thread overview]
Message-ID: <Pine.LNX.4.64.1204122325580.15801@axis700.grange> (raw)
In-Reply-To: <CACRpkdbjNqsWvv_0roFLGm_uzVFCOfeaek65=bxiUhU3XQXwKA@mail.gmail.com>
On Tue, 3 Apr 2012, Linus Walleij wrote:
> On Fri, Mar 30, 2012 at 12:38 PM, Russell King - ARM Linux
> <linux@arm.linux.org.uk> wrote:
>
> > Actually, I think that's the key thing: the handshake lines should be
> > the data involved in channel selection and nothing else - though as I've
> > pointed out already, there's the complication for external MUXing between
> > the DMA engine and the peripheral which makes that non-trivial.
>
> I think you're onto something here, and it sounds it could be made
> elegant to me.
Now, how do we proceed from here? Do I understand it right, that Russell
would like to implement his ideas? Any idea when this is likely to happen?
If not too soon, maybe we could / should work out an intermediate
solution? How about, for example: I resubmit my patch, but don't claim it
for general use, rather keep it sh-own (even though the generic part will
have no hardware-specific code in it). Then we can implement both sh
driver on top of that. Of course, the dubious use of the struct
dma_chan::private field will remain. But it is there now anyway, so, this
will not introduce any new uses of .private or extend the existing one.
And once we have a generic way to request specific DMA channels, we'll
switch the shdma driver(s) to it too.
Thanks
Guennadi
>
> As for muxed request signals, we would need to hook in some
> cascading framework if we want it all generic.
>
> On the Nomadik 8815 (which I now have up and running)
> the system has two PL080 instances, each with 16 channels.
> However the same request lines are *partly* routed to *both*
> PL080 instances. This would be one of the things we could
> solve with a line-oriented approach, say we have this set
> of DMA lines, and then defined a group of lines per
> DMAC instance, then by stating that this device has this
> request line we can infer the suitable DMA slave engines
> and select one with a free channel to run the transfer.
>
> It does require some upfront code, but I'm sure it can be
> made to work.
>
> Yours,
> Linus Walleij
>
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/
next prev parent reply other threads:[~2012-04-12 21:33 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
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 [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Pine.LNX.4.64.1204122325580.15801@axis700.grange \
--to=g.liakhovetski@gmx.de \
--cc=jassisinghbrar@gmail.com \
--cc=lethal@linux-sh.org \
--cc=linus.walleij@linaro.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@arm.linux.org.uk \
--cc=magnus.damm@gmail.com \
--cc=vinod.koul@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).