From: jon-hunter@ti•com (Jon Hunter)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH V3 1/2] of: Add generic device tree DMA helpers
Date: Wed, 13 Jun 2012 17:32:22 -0500 [thread overview]
Message-ID: <4FD914F6.6000402@ti.com> (raw)
In-Reply-To: <201206090004.10086.arnd@arndb.de>
Hi Arnd,
On 06/08/2012 07:04 PM, Arnd Bergmann wrote:
> On Friday 08 June 2012, Jon Hunter wrote:
>> On 05/21/2012 03:32 PM, Stephen Warren wrote:
>>> On 05/21/2012 12:18 PM, Arnd Bergmann wrote:
>>>> On Monday 21 May 2012, Stephen Warren wrote:
>>>>>
>>>>> If so, that seems a little odd; you have to request a DMA channel for
>>>>> "TX", but then end up having the common code check all the entries in
>>>>> the dmas property since it can't know which are TX, and then have the
>>>>> wrong ones almost accidentally fail, since the DMAC will then determine
>>>>> that it can't support TX on the RX DMA request IDs.
>>>>
>>>> I think the direction must be encoded in a way that does not depend on
>>>> the binding for the specific controller. There are two ways I can see
>>>> how we might do it:
>>>>
>>>> 1. have separate property names for tx and rx channels, and probably
>>>> one for combined rx/tx channels
>>>
>>>> 2. define the second cell in each channel specifier to be the direction
>>>> in a predefined format, followed by the other (controller specific)
>>>> attributes, if any.
>>>
>>> In this option, lets say bit 0 is 0==TX, 1==RX (or perhaps 2 bits if
>>> combined TX/RX is needed)
>>>
>>> Then, we could reserve say bits 7:1 as client DMA request ID.
>>>
>>> And then have bits 31:8 as DMAC specific data.
>>>
>>> Wouldn't that allow us to have our cake and eat it?
>>
>> Sorry for not responding sooner.
>>
>> It seems to me we were pretty close on alignment. In fact, I was quite
>> happy with Steven's 2nd to last proposal of ...
>>
>> simple 1 req:
>> dmas = <0 &dmac1 xxx>;
>>
>> simple 2 req:
>> dmas = <0 &dmac1 xxx 1 &dmac1 yyy>;
>>
>> multiple dmacs:
>> dmas = <0 &dmac1 xxx 0 &dmac2 zzz 1 &dmac1 yyy>;
>>
>> Arnd, I know that you had some concerns. However, in the above case I
>> would expect that the 3rd parameter be optional and it can be some sort
>> of match variable. In other words, we don't care how the 32-bits are
>> encoded or what they represent but they would be used appropriately by
>> the xlate function being used. So the xlate and this "match" variable
>> would have to speak the same language.
>
> I would at least put the &dmac part first to be consistent with other
> bindings that refer to some node. That controller should then be
> able to specify the number of additional cells used to describe the
> dma request. We can define that the first cell after the controller
> phandle is always the same thing, e.g. the direction (in/out/inout)
> or a client-specific ID or a combination of that with other predefined
> bits that are not dependent on dma controller specifics.
I agree with putting the &dmac phandle first, that makes sense.
> As I said previously, I think just encoding the direction but not
> the client specific ID (meaning we would have to disambiguate
> the more complex cases that Stephen mentioned using a dma-names
> property) would be the best because it keeps the common case simple,
> but I could live with other things going in there too.
Ok, so you are saying that there are some DMA controllers where there is
no channel/request ID and only a direction is needed? So an even simpler
case than what I had imagined.
So in that case, I don't see why the first cell after the phandle could
not be an index which could be either a direction or request-id and then
the next cell after that be a secondary match variable.
So simple case with just a index (either req-id or direction) ...
dmas = <&dmac0 index>
More complex case ...
dmas = <&dmac0 index match>
For example, for OMAP index = req-id and match = direction ...
dmas = <&dmac0 req-id direction>
Or am I way off the page?
Cheers
Jon
next prev parent reply other threads:[~2012-06-13 22:32 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
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 [this message]
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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