linux-kernel - Re: [PATCH v4] dma: Add Xilinx AXI Direct Memory Access Engine driver support

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Message-ID: <ad1002303e814d53866349674d22fc11@BY2FFO11FD039.protection.gbl>
Date:	Fri, 20 Feb 2015 11:42:31 +0100
From:	Michal Simek <michal.simek@...inx.com>
To:	Vinod Koul <vinod.koul@...el.com>,
	Appana Durga Kedareswara Rao <appana.durga.rao@...inx.com>
CC:	Arnd Bergmann <arnd@...db.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Srikanth Vemula <svemula@...inx.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Srikanth Thokala <sthokal@...inx.com>,
	"dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	Anirudha Sarangi <anirudh@...inx.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"dan.j.williams@...el.com" <dan.j.williams@...el.com>
Subject: Re: [PATCH v4] dma: Add Xilinx AXI Direct Memory Access Engine driver
 support

Hi Vinod,

On 02/20/2015 07:29 AM, Vinod Koul wrote:
> On Sat, Feb 14, 2015 at 02:21:52PM +0000, Appana Durga Kedareswara Rao wrote:
>> Hi Vinod,
>>
>>
>>> -----Original Message-----
>>> From: Vinod Koul [mailto:vinod.koul@...el.com]
>>> Sent: Thursday, February 12, 2015 3:05 PM
>>> To: Appana Durga Kedareswara Rao
>>> Cc: Arnd Bergmann; linux-arm-kernel@...ts.infradead.org;
>>> devicetree@...r.kernel.org; Srikanth Vemula; linux-
>>> kernel@...r.kernel.org; Srikanth Thokala; dmaengine@...r.kernel.org;
>>> robh+dt@...nel.org; Michal Simek; Anirudha Sarangi;
>>> grant.likely@...aro.org; dan.j.williams@...el.com
>>> Subject: Re: [PATCH v4] dma: Add Xilinx AXI Direct Memory Access Engine
>>> driver support
>>>
>>> On Thu, Jan 29, 2015 at 11:24:41AM +0000, Appana Durga Kedareswara Rao
>>> wrote:
>>>>>  Earlier in the driver we are embedding dma_slave_config into custom
>>>>> structs But Lars suggested to modify it. please refer to the below
>>>>> thread for more details.
>>>>>  http://www.spinics.net/lists/dmaengine/msg00010.html
>>>>>
>>>>>  And later we thought of creating a separate private member in
>>>>> dma_slave_config for sharing additional configuration between slave
>>>>> device and dma engine Or a new dma_ctrl_cmd like
>>>>>
>>> FSLDMA_EXTERNAL_START(http://www.kernelhub.org/?msg=405535&p=2 )
>>>>>
>>>>>  Finally Vinod was ok with the existing suggestion so we dropped the
>>>>> above thought.
>>>>>
>>>>>  @Vinod : Could you please comment on this.
>>> FSLDMA_EXTERNAL_START has been removed, and you cna use the removal
>>> as a guidance of how to solve your issue
>>>
>>
> Please limit you mailer to set wrap at 80 chars, otherwise it becomes
> unreadable
> 
>> The current VDMA driver that got merged in the open source and the
>> current patch (dma: xilinx dma v4) Srikanth T submitted both contains the
>> Similar implementation that you pointed as above(I mean similar to the
>> free scale dma driver).
>>
>> The discussion starts here is why we need the header file(Xilinx_dma.h) in
>> the include/linux/amba/Xilinx_dma.h  folder.
>>
>> Like for FSL DMA it is got defined (fsl_dma_external_start) as a function
>> prototype in include/linux/fsldma.h And it is being getting used in the
>> drivers/misc/carma/carma-fpga-program.c
>>
>> Similarly in the Xilinx VDMA driver(xilinx_vdma_channel_set_config )
>> defined as a function prototype in the include/linux/amba/xilinx_dma.h And
>> is being used by Xilinx videos  drivers.  Those video driver need to use
>> the (xilinx_vdma_channel_set_config) which requires this global header
>> file.
>>
>> Could you please suggest us whether that header file (Xilinx_dma.h) should
>> be there  in include/linux/amba or we should move it to include/linux?
>> And any functional comments for this v4 patch?
> Let me ask you a question, what is the relation of xilinx_dma with amba?
> 
> If none then only include/linux/ seems to be the right choice. If not then
> amba maybe okay but you need to provide justfication why it should be in amba?

I see your point. I think there is real reason to have this header in amba.
The reason for that was that xilinx_dma.h was added there.

Anyway there is include/linux/dma/ folder. Is it ok to move xilinx_dma.h there
too? The same with this dma one.

Thanks,
Michal


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