Hi Jassi,
On 05/16/2012 07:37 AM, Jassi Brar wrote:
> Hi Jon,
>
> On 16 May 2012 06:41, Jon Hunter <jon-hunter@xxxxxx> wrote:
>> On 05/04/2012 02:01 PM, Jassi Brar wrote:
>>>
>>> + i2c1: i2c@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.
> If you read the whole exchange between I and Stephen, we converged on a
> scheme of clients' node having nothing to specify and DMAC told all about
> every client in one palce. Which resembles closer to reality and is
> much simpler.
> I already started on a patchset and should be able submit for review
> in a day or two.
Ok. I look forward to your implementation :-)
Jon
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