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

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Message-ID: <20150220062934.GX21387@intel.com>
Date:	Fri, 20 Feb 2015 11:59:34 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	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>,
	Michal Simek <michals@...inx.com>,
	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

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?

-- 
~Vinod

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