From: swarren@wwwdotorg•org (Stephen Warren)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH V3 1/2] of: Add generic device tree DMA helpers
Date: Wed, 16 May 2012 10:15:16 -0600 [thread overview]
Message-ID: <4FB3D294.4020505@wwwdotorg.org> (raw)
In-Reply-To: <4FB3CF44.4040603@ti.com>
On 05/16/2012 10:01 AM, Jon Hunter wrote:
...
> By the way, I do see your point. You wish to describe the all the
> mappings available to all dma controllers and then set a mapping in the
> device tree. Where as I am simply setting a mapping and do not list all
> other possibilities (assuming that there some).
>
> What is still unclear to me, is if you use this token approach how
> readable is the device-tree? For example, if you have a client that can
> use one of two dmac and for each dmac the request/channel number is
> different, then by using a global token how can I determine what the
> options available for this client are?
>
> Take your example ...
>
> mmc1: mmc at 13002000 {
> ...
> dma_tx = <891> //some platform-wide unique value
> dma_rx = <927> //some platform-wide unique value
> ...
> };
I believe those properties (in the DMA client) should be completely
omitted; there's no need for them.
Also, we definitely should not be using "some platform-wide unique
value", but rather the phandle of the DMA client, plus some
client-defined client channel ID. ...
(oh, and - rather than _ is idiomatic for DT property names)
> DMAC's Node:-
>
> pdma2: pdma at 10800000 {
> .......
> dma_map = <891, 7>, // Map mmc1_tx onto i/f 7
> <927, 8>, // Map mmc1_rx onto i/f 8
> .......
> };
So this would become:
pdma2: pdma at 10800000 {
.......
dma-map =
... entries for channels 0.. 6
<&mmc1, 0>, // Map mmc1_tx onto i/f 7
<&mmc1, 1>, // Map mmc1_rx onto i/f 8
... ;
.......
};
This (a) follows existing DT practice of using phandle + specifier, and
(b) makes it easy to know exactly what clients you're talking about,
since all you need to do is search for the label "mmc1" throughout the DT.
> But now I have another dmac which has the following options ...
>
> pdma1: pdma at 10000000 {
> .......
> dma_map = <598, 2>, // Map mmc1_tx onto i/f 2
> <230, 3>, // Map mmc1_rx onto i/f 3
> .......
> };
Which would become something very similar:
pdma1: pdma at 10000000 {
.......
dma-map =
... entries for channels 0.. 1
<&mmc1, 0>, // Map mmc1_tx onto i/f 2
<&mmc1, 1>, // Map mmc1_rx onto i/f 3
... ;
.......
};
Note that dma-map here is describing the list of DMA requests that the
DMA controller knows about. As far as the binding goes, these are
irrelevant to channels; only the driver for the DMAC knows whether it
needs to use a specific channel ID to service a particular DMA request
signal, or not.
> Other than using a comment or yet another token to represent the client,
> it is not clear from the arbitrary token value itself what my options are.
>
> One way around this would be to have an enable/disable flag along with
> the token such as ...
>
> mmc1: mmc at 13002000 {
> ...
> dma_tx = <891, 1> // default tx channel
> dma_rx = <927, 1> // default rx channel
> dma_tx = <598, 0> // other available tx channel
> dma_rx = <230, 0> // other available rx channel
> ...
> };
>
> That being said, we could take the same approach with using the dmac
> phandle instead of the token. So you would have ...
>
>
> mmc1: mmc at 13002000 {
> ...
> // phandle + channel + enable/disable
> dma_tx = <pdma0, 7, 1> // default tx channel
> dma_rx = <pdma0, 8, 1> // default rx channel
> dma_tx = <pdma1, 2, 0> // other available tx channel
> dma_rx = <pdma1, 3, 0> // other available rx channel
> ...
> };
>
> Then you could eliminate the random token and dma map from the dmac.
> Seems easier to read too.
next prev parent reply other threads:[~2012-05-16 16:15 UTC|newest]
Thread overview: 129+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-30 21:17 [PATCH V3 1/2] of: Add generic device tree DMA helpers Jon Hunter
2012-05-03 22:26 ` Stephen Warren
2012-05-03 23:25 ` Russell King - ARM Linux
2012-05-04 12:39 ` Arnd Bergmann
2012-05-04 15:06 ` Jon Hunter
2012-05-04 15:14 ` Russell King - ARM Linux
2012-05-04 18:21 ` Stephen Warren
2012-05-04 19:19 ` Jon Hunter
2012-05-04 6:56 ` Jassi Brar
2012-05-04 15:17 ` Jon Hunter
2012-05-04 19:01 ` Jassi Brar
2012-05-04 19:23 ` Arnd Bergmann
2012-05-05 17:10 ` Jassi Brar
2012-05-07 15:53 ` Stephen Warren
2012-05-07 17:19 ` Jassi Brar
2012-05-08 16:35 ` Stephen Warren
2012-05-08 19:09 ` Jassi Brar
2012-05-09 12:30 ` Arnd Bergmann
2012-05-09 19:10 ` Stephen Warren
2012-05-09 21:38 ` Jassi Brar
2012-05-10 17:00 ` Stephen Warren
2012-05-10 19:59 ` Jassi Brar
2012-05-11 19:28 ` Stephen Warren
2012-05-11 21:06 ` Jassi Brar
2012-05-11 23:51 ` Stephen Warren
2012-05-12 13:40 ` Jassi Brar
2012-05-16 1:05 ` Jon Hunter
2012-05-17 13:18 ` Russell King - ARM Linux
2012-05-07 17:21 ` Arnd Bergmann
2012-05-16 1:11 ` Jon Hunter
2012-05-16 12:37 ` Jassi Brar
2012-05-16 13:15 ` Jon Hunter
2012-05-16 15:44 ` Stephen Warren
2012-05-16 16:04 ` Jon Hunter
2012-05-16 16:01 ` Jon Hunter
2012-05-16 16:15 ` Stephen Warren [this message]
2012-05-16 16:22 ` Jassi Brar
2012-05-16 17:09 ` Jon Hunter
2012-05-16 19:42 ` Arnd Bergmann
2012-05-16 21:16 ` Jassi Brar
2012-05-17 19:32 ` Stephen Warren
2012-05-18 17:12 ` Jassi Brar
2012-05-18 21:04 ` Arnd Bergmann
2012-05-16 23:59 ` Stephen Warren
2012-05-17 4:05 ` Jassi Brar
2012-05-18 20:49 ` Arnd Bergmann
2012-05-18 21:07 ` Stephen Warren
2012-05-18 21:43 ` Arnd Bergmann
2012-05-18 22:20 ` Stephen Warren
2012-05-19 8:44 ` Arnd Bergmann
2012-05-21 17:33 ` Stephen Warren
2012-05-21 18:18 ` Arnd Bergmann
2012-05-21 20:32 ` Stephen Warren
2012-06-08 19:04 ` Jon Hunter
2012-06-09 0:04 ` Arnd Bergmann
2012-06-13 22:32 ` Jon Hunter
2012-06-14 4:45 ` Jassi Brar
2012-06-14 11:48 ` Arnd Bergmann
2012-06-14 15:39 ` Jon Hunter
2012-06-15 8:40 ` Arnd Bergmann
2012-06-22 22:52 ` Jon Hunter
2012-06-22 23:12 ` Russell King - ARM Linux
2012-06-25 16:51 ` Jon Hunter
2012-06-25 18:04 ` Vinod Koul
2012-06-25 20:30 ` Arnd Bergmann
2012-06-26 9:40 ` Vinod Koul
2012-06-26 14:59 ` Arnd Bergmann
2012-06-26 17:50 ` Vinod Koul
2012-06-26 20:27 ` Arnd Bergmann
2012-06-27 13:45 ` Vinod Koul
2012-06-27 15:20 ` Arnd Bergmann
2012-07-13 6:45 ` Vinod Koul
2012-07-13 21:52 ` Guennadi Liakhovetski
2012-07-17 19:24 ` Arnd Bergmann
2012-07-20 4:00 ` Vinod Koul
2012-07-20 8:39 ` Arnd Bergmann
2012-07-20 9:37 ` Vinod Koul
2012-07-24 19:07 ` Jon Hunter
2012-07-24 19:27 ` Arnd Bergmann
2012-07-26 6:42 ` Vinod Koul
2012-07-26 7:14 ` Arnd Bergmann
2012-07-26 11:28 ` Vinod Koul
2012-07-26 15:53 ` Jon Hunter
2012-07-31 11:06 ` Vinod Koul
2012-07-26 17:43 ` Jon Hunter
2012-07-31 11:12 ` Vinod Koul
2012-08-01 20:43 ` Jon Hunter
2012-08-03 9:55 ` Vinod Koul
2012-07-20 9:08 ` Robert Jarzmik
2012-07-20 9:41 ` Vinod Koul
2012-07-26 4:56 ` zhangfei gao
2012-07-23 21:29 ` Stephen Warren
2012-07-24 7:19 ` Arnd Bergmann
2012-07-24 16:04 ` Stephen Warren
2012-07-24 18:55 ` Arnd Bergmann
2012-07-24 12:54 ` Sergei Shtylyov
2012-07-06 11:36 ` Guennadi Liakhovetski
2012-07-06 15:28 ` Arnd Bergmann
2012-07-06 15:43 ` Guennadi Liakhovetski
2012-07-06 17:31 ` Arnd Bergmann
2012-07-06 21:01 ` Russell King - ARM Linux
2012-07-06 20:57 ` Russell King - ARM Linux
2012-07-06 22:49 ` Guennadi Liakhovetski
2012-07-13 6:51 ` Vinod Koul
2012-06-14 15:17 ` Guennadi Liakhovetski
2012-06-14 21:52 ` Jon Hunter
2012-06-15 8:41 ` Guennadi Liakhovetski
2012-06-15 9:00 ` Arnd Bergmann
2012-06-15 9:18 ` Guennadi Liakhovetski
2012-06-15 11:27 ` Arnd Bergmann
2012-06-15 16:11 ` Mitch Bradley
2012-06-16 6:56 ` Arnd Bergmann
2012-06-21 11:21 ` Guennadi Liakhovetski
2012-06-21 14:56 ` Arnd Bergmann
2012-05-17 13:22 ` Russell King - ARM Linux
2012-05-17 13:52 ` Mark Brown
2012-05-17 14:16 ` Russell King - ARM Linux
2012-05-16 16:16 ` Jassi Brar
2012-05-16 17:12 ` Jon Hunter
2012-05-16 17:24 ` Jassi Brar
2012-05-16 17:37 ` Jon Hunter
2012-05-16 17:46 ` Stephen Warren
2012-05-16 18:03 ` Jon Hunter
2012-05-04 15:22 ` Jon Hunter
2012-05-04 15:56 ` Arnd Bergmann
2012-05-04 17:19 ` Jon Hunter
2012-05-04 19:06 ` Arnd Bergmann
2012-05-04 19:26 ` Jon Hunter
2012-05-04 18:30 ` Stephen Warren
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