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, 16 May 2012 11:04:29 -0500 [thread overview]
Message-ID: <4FB3D00D.2050503@ti.com> (raw)
In-Reply-To: <4FB3CB58.4050107@wwwdotorg.org>
On 05/16/2012 10:44 AM, Stephen Warren wrote:
> On 05/16/2012 07:15 AM, Jon Hunter wrote:
>> Hi Jassi,
>>
>> On 05/16/2012 07:37 AM, Jassi Brar wrote:
>>> Hi Jon,
>>>
>>> On 16 May 2012 06:41, Jon Hunter <jon-hunter@ti•com> wrote:
>>>> On 05/04/2012 02:01 PM, Jassi Brar wrote:
>>>>>
>>>>> + i2c1: i2c at 1 {
>>>>> + ...
>>>>> + dma = <&sdma 2 1 &sdma 3 2>;
>>>>> + ...
>>>>> + };
>>>>>>
>>>>> I see this requires a client driver to specify a particular req_line on a
>>>>> particular dma controller. I am not sure if this is most optimal.
>>>>
>>>> Actually, no. The phandle in the DT specifies the DMA controller to use.
>>>> Then the client simply asks for a channel with a particular property,
>>>> for example, DMA_MEM_TO_DEV (ie. TX) and the channel information is return.
>>>>
>>> See below.
>>>
>>>>> I think such client->req_line map should be provided to the dmac controller
>>>>> driver via its dt node in some format. The dmac driver could then populate
>>>>> a dma_chan, or similar, only for that req_line and not for the unused one
>>>>> which otherwise could also have served the same client.
>>>>>
>>>>> Ideally the I2C driver should simply ask, say, a channel for TX and another
>>>>> for RX, everything else should already be setup via dmac's dt nodes.
>>>>
>>>> Yes that is the intention here.
>>>>
>>> But the client is required to specify the dmac that would serve it.
>>> Which is more
>>> than simply asking for "some suitable channel".
>>
>> No this is not the case with what I propose. The client knows nothing
>> about the dmac.
>
> I think you're both talking about slightly different things.
>
> Jon: You're talking about the driver code.
> Jassi: You're talking about the device tree.
Yes you are right. However, I do see Jassi's point now.
> By including a property in the DMA client's DT node that describes which
> DMA controller services it, the device (the DT node) "knows" about the
> DMA controllers.
>
> By moving the information to the DMA controller and specifying which DMA
> clients can be serviced, that DMA client DT node no longer contains any
> information about the DMA controller that serves it, and hence it's not
> bound to a single controller, and hence can select from 1 of n
> controllers at run-time if applicable given the HW.
Yes I see the need for this. My concern (and I just sent another
follow-up) was how readable is the device-tree for a human by using such
a token. Is it intuitive enough for a human to understand the options
available.
Cheers
Jon
next prev parent reply other threads:[~2012-05-16 16:04 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 [this message]
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
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
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=4FB3D00D.2050503@ti.com \
--to=jon-hunter@ti$(echo .)com \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
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