From: nicolas.ferre@atmel•com (Nicolas Ferre)
To: linux-arm-kernel@lists•infradead.org
Subject: [RFC PATCH 1/2] of: Add generic device tree DMA helpers
Date: Mon, 27 Feb 2012 18:28:02 +0100 [thread overview]
Message-ID: <4F4BBD22.6090104@atmel.com> (raw)
In-Reply-To: <4F4B91B8.8000805@ti.com>
On 02/27/2012 03:22 PM, Cousson, Benoit :
> On 2/27/2012 2:09 PM, Nicolas Ferre wrote:
>> On 02/23/2012 04:57 PM, Cousson, Benoit :
>>> On 2/23/2012 4:51 PM, Nicolas Ferre wrote:
>>>> On 02/23/2012 11:03 AM, Cousson, Benoit :
>>>>> Salut Nico,
>>>>
>>>> Coucou Benoit ;-)
>>>>
>>>>> On 2/22/2012 11:59 AM, Nicolas Ferre wrote:
>>>>>> On 01/27/2012 06:29 PM, Cousson, Benoit :
>>>>>>> Add some basic helpers to retrieve a DMA controller device_node
>>>>>>> and the DMA request line number.
>>>>>>>
>>>>>>> For legacy reason another API will export the DMA request number
>>>>>>> into a Linux resource of type IORESOURCE_DMA.
>>>>>>> This API is usable only on system with an unique DMA controller.
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> I followed that discussion and I like very much the biding that
>>>>>> Benoit
>>>>>> is proposing. It will help me a lot with my current work on Atmel DMA
>>>>>> controller.
>>>>>>
>>>>>> If I understand correctly, some rework is needed before it can be
>>>>>> integrated in a stable git tree (I mean before we can base our
>>>>>> work on
>>>>>> top of it). So, in the meantime, what should I do to help and make
>>>>>> things go forward? to be quite frank, I would be interested to have a
>>>>>> working DMA enabled device soon ;-)
>>>>>
>>>>> Me too, but unfortunately, I was busy trying to add irq_domain and
>>>>> fixing issues with SPARSE_IRQ on OMAP :-(
>>>>
>>>> Been there, loved that ;-)
>>>>
>>>>>> Do you think that 3.4 is out of reach?
>>>>>
>>>>> Maybe not, from the comments, it looks like we should add a .xlate
>>>>> callback to allow any custom parsing of the DMA nodes attributes.
>>>>>
>>>>> I'll be more than happy, if you can finalize that patch :-)
>>>>
>>>> I will try to figure out what I can understand from the irq
>>>> mechanism of
>>>> .xlate and try to see if I can implement it on top of your patch.
>>>
>>> In fact that dma code is a big copy/paste of the of/gpio one and gpio
>>> was already managing .xlate function.
>>> I removed it because I thought it was useless for the DMA :-)
>>>
>>> You might just have to copy the original code...
>>
>> The thing is that with gpio, we can rely on the gpio_chip structure for
>> having a common storage location of such .xlate callbacks.
>> In our DMA case, I guess that we should not cling to dmaengine
>> infrastructure because not all of us are using it right now.
>
> Yep, that's the main issue compared to GPIO or IRQ.
>
>> So, maybe we should provide some simple "xlate" helpers like the
>> irqdomain ones. But I fear that a "callback" directly called from the
>> of_get_dma_request() function is not possible (the gpio code model).
>
> I think a well that we cannot much but a simple very abstract callback
> since we do not have any formal DMA representation?
>
> I'm not sure to understand you concern?
Well, in fact I cannot find a place where to store a "xlate" callback:
- it have to be provided by the DMA controller (the one pointed out by
the phandle) and not the caller of the of_get_dma_request() funtion
- it has to be generic enough to match the dmaengine/non-dmaengine cases
(so it cannot be stored in the dmaengine "struct dma_device").
So I guess that the very basic idea of returning the full DMA specifier
(struct of_phandle_args) is the best... My only concern is that the
"helper" becomes very short and empty in this case...
Bye,
--
Nicolas Ferre
next prev parent reply other threads:[~2012-02-27 17:28 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-27 17:29 [RFC PATCH 1/2] of: Add generic device tree DMA helpers Cousson, Benoit
2012-01-27 18:13 ` Stephen Warren
2012-01-27 20:36 ` Cousson, Benoit
2012-01-28 18:12 ` Grant Likely
2012-01-28 18:06 ` Grant Likely
2012-01-31 21:26 ` Cousson, Benoit
2012-02-02 4:52 ` Grant Likely
2012-01-31 23:09 ` Russell King - ARM Linux
2012-02-01 10:50 ` Cousson, Benoit
2012-02-02 8:45 ` Russell King - ARM Linux
2012-02-02 8:54 ` Cousson, Benoit
2012-02-22 10:59 ` Nicolas Ferre
2012-02-23 10:03 ` Cousson, Benoit
2012-02-23 15:51 ` Nicolas Ferre
2012-02-23 15:57 ` Cousson, Benoit
2012-02-27 13:09 ` Nicolas Ferre
2012-02-27 14:22 ` Cousson, Benoit
2012-02-27 17:28 ` Nicolas Ferre [this message]
2012-02-29 14:54 ` [RFC PATCH] of: DMA helpers: manage generic requests specification Nicolas Ferre
2012-02-29 20:54 ` Stephen Warren
2012-03-05 13:14 ` Cousson, Benoit
2012-03-05 18:30 ` Stephen Warren
2012-03-05 19:57 ` Russell King - ARM Linux
2012-03-05 10:55 ` Cousson, Benoit
2012-03-05 15:36 ` Grant Likely
2012-03-14 17:47 ` Nicolas Ferre
2012-03-14 18:16 ` Stephen Warren
2012-03-15 8:38 ` [PATCH] of: Add generic device tree DMA helpers Nicolas Ferre
2012-03-15 9:22 ` Arnd Bergmann
2012-03-15 9:26 ` Russell King - ARM Linux
2012-03-15 10:09 ` Arnd Bergmann
2012-03-17 9:42 ` Grant Likely
2012-03-17 16:03 ` Arnd Bergmann
2012-03-18 9:08 ` Grant Likely
2012-03-15 10:27 ` Thierry Reding
2012-03-17 10:47 ` Grant Likely
2012-03-18 9:22 ` Thierry Reding
2012-03-18 15:10 ` Arnd Bergmann
2012-03-18 18:22 ` Grant Likely
2012-03-19 13:02 ` Mark Brown
2012-03-19 15:01 ` Arnd Bergmann
2012-03-19 15:07 ` Stephen Warren
2012-03-19 15:45 ` Arnd Bergmann
2012-03-19 16:54 ` Stephen Warren
2012-03-15 16:30 ` Cousson, Benoit
2012-03-15 19:57 ` Russell King - ARM Linux
2012-03-15 20:41 ` Arnd Bergmann
2012-03-15 21:39 ` Cousson, Benoit
2012-03-15 21:55 ` Russell King - ARM Linux
2012-03-16 9:56 ` Arnd Bergmann
2012-03-20 14:02 ` Matt Porter
2012-03-15 23:45 ` Nicolas Pitre
2012-03-16 10:03 ` Arnd Bergmann
2012-03-16 11:19 ` Cousson, Benoit
2012-03-16 12:04 ` Arnd Bergmann
2012-03-16 13:28 ` Cousson, Benoit
2012-03-16 13:36 ` Nicolas Ferre
2012-03-17 9:40 ` Grant Likely
2012-03-18 20:13 ` Arnd Bergmann
2012-03-18 20:44 ` Grant Likely
2012-03-18 21:58 ` Arnd Bergmann
2012-03-18 22:12 ` Arnd Bergmann
2012-03-19 13:37 ` Nicolas Ferre
2012-03-19 15:20 ` Russell King - ARM Linux
2012-03-19 15:58 ` Cousson, Benoit
2012-03-19 13:30 ` Nicolas Ferre
2012-03-19 14:06 ` Arnd Bergmann
2012-03-19 15:33 ` Russell King - ARM Linux
2012-03-19 16:11 ` Arnd Bergmann
2012-03-19 18:06 ` Jassi Brar
2012-03-19 16:31 ` Nicolas Ferre
2012-03-19 17:49 ` Cousson, Benoit
2012-03-19 14:45 ` Grant Likely
2012-03-20 14:54 ` Nicolas Ferre
2012-03-20 10:13 ` [PATCH v2 1/2] " Nicolas Ferre
2012-03-20 10:13 ` [PATCH 2/2] of: selftest/dma: Add selftest for new DT DMA request helpers Nicolas Ferre
2012-03-20 14:16 ` Grant Likely
2012-03-20 10:17 ` [PATCH] of: dma/fixup Nicolas Ferre
2012-03-20 13:03 ` [PATCH v2 1/2] of: Add generic device tree DMA helpers Arnd Bergmann
2012-03-20 15:38 ` Stephen Warren
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