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: Tue, 24 Jul 2012 14:07:43 -0500 [thread overview]
Message-ID: <500EF27F.6050905@ti.com> (raw)
In-Reply-To: <1342777047.1726.435.camel@vkoul-udesk3>
Hi Vinod,
On 07/20/2012 04:37 AM, Vinod Koul wrote:
> On Fri, 2012-07-20 at 08:39 +0000, Arnd Bergmann wrote:
>> On Friday 20 July 2012, Vinod Koul wrote:
>>>> Required property:
>>>> dmas: list of one or more dma specifiers, each consisting of
>>>> - phandle pointing to dma controller node
>>>> - flags word, a bit map that can hold these flags
>>>> * 0x00000001 channel can be used for transfer from device
>>>> * 0x00000002 channel can be user for transfer to device
>>>
>>> Is this for identifying which channel is for TX and RX? If not I am not
>>> sure I understood it well
>>
>> Yes, but we can potentially add more flags here.
>>
>> The argument we had when coming up with this was roughly:
>>
>> * we need to identify which specifiers are referring to the same
>> conceptual channel and can be used as alternatives
>> * this could be done just using the dma-names property, but making
>> dma-names mandatory adds complexity for everyone.
>> * Most devices have just one or two channels, and if they have two,
>> there is usually one input and one output.
>>
>> => if the common dmaengine code can find out whether a channel is
>> input or output without looking at the dmac driver specific configuration,
>> we don't need to add dma-names in most cases, but just let the client
>> driver ask for "give me a channel with these flags".
> No we don't export the direction of the channel and usually channel can
> be configured either way.
So yes I can see that a channel itself could be configured to support a
given direction, but when we ask for a channel via dma_request_channel()
we are going to get a channel that matches the criteria we pass using
the filter parameter. So here the thinking was that "flags" is a filter
parameter that the user could specify and one example being direction
but it could be something else too.
> But from a client POV it makes sense as with the given direction you
> would need a specific request line for a channel. So this is right.
> But direction is something I don't expect to be used for "give me a
> channel"
Ok. The thought was that the user would have the following means of
requesting a channel ...
1. By name
2. By a filter parameter (flags)
3. By name and a filter parameter
So we would have the following APIs ...
struct dma_chan
*of_dma_request_channel(struct device_node *node, unsigned int flags);
struct dma_chan
*of_dma_request_named channel(struct device_node *node, char *name,
unsigned int flags);
In both of these the filter parameter flags is optional.
Let me know your thoughts on this.
Cheers
Jon
next prev parent reply other threads:[~2012-07-24 19:07 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
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 [this message]
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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