RE: [PATCH v4] dma: Add Xilinx AXI Direct Memory Access Engine driver support

[Appana Durga Kedareswara Rao]

Ping !

> -----Original Message-----
> From: Appana Durga Kedareswara Rao
> Sent: Thursday, January 29, 2015 4:55 PM
> To: 'Arnd Bergmann'; 'vinod.koul@xxxxxxxxx'
> Cc: 'linux-arm-kernel@xxxxxxxxxxxxxxxxxxx'; 'devicetree@xxxxxxxxxxxxxxx';
> 'vinod.koul@xxxxxxxxx'; Srikanth Vemula; 'linux-kernel@xxxxxxxxxxxxxxx';
> Srikanth Thokala; 'dmaengine@xxxxxxxxxxxxxxx'; 'robh+dt@xxxxxxxxxx';
> Michal Simek; Anirudha Sarangi; 'grant.likely@xxxxxxxxxx';
> 'dan.j.williams@xxxxxxxxx'
> Subject: RE: [PATCH v4] dma: Add Xilinx AXI Direct Memory Access Engine
> driver support
>
> Hi Vinod,
>
>
> > -----Original Message-----
> > From: Appana Durga Kedareswara Rao
> > Sent: Monday, January 19, 2015 7:39 PM
> > To: 'Arnd Bergmann'; vinod.koul@xxxxxxxxx
> > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx;
> > vinod.koul@xxxxxxxxx; Srikanth Vemula; linux-kernel@xxxxxxxxxxxxxxx;
> > Srikanth Thokala; dmaengine@xxxxxxxxxxxxxxx; robh+dt@xxxxxxxxxx;
> > Michal Simek; Anirudha Sarangi; grant.likely@xxxxxxxxxx;
> > dan.j.williams@xxxxxxxxx
> > Subject: RE: [PATCH v4] dma: Add Xilinx AXI Direct Memory Access
> > Engine driver support
> >
> > Hi Arnd,
> >
> > > -----Original Message-----
> > > From: Arnd Bergmann [mailto:arnd@xxxxxxxx]
> > > Sent: Friday, October 24, 2014 7:29 PM
> > > To: Appana Durga Kedareswara Rao
> > > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> > > devicetree@xxxxxxxxxxxxxxx; vinod.koul@xxxxxxxxx; Srikanth Vemula;
> > > linux-kernel@xxxxxxxxxxxxxxx; Srikanth Thokala;
> > > dmaengine@xxxxxxxxxxxxxxx; robh+dt@xxxxxxxxxx; Michal Simek;
> > > Anirudha Sarangi; grant.likely@xxxxxxxxxx; dan.j.williams@xxxxxxxxx
> > > Subject: Re: [PATCH v4] dma: Add Xilinx AXI Direct Memory Access
> > > Engine driver support
> > >
> > > On Friday 24 October 2014 12:08:26 Appana Durga Kedareswara Rao
> wrote:
> > > > From: Arnd Bergmann [mailto:arnd@xxxxxxxx]
> > > > > On Tuesday 21 October 2014 09:06:13 Appana Durga Kedareswara Rao
> > > wrote:
> > > > > > The above mentioned API's  and structures will be used by the
> > > > > > dma test client driver's to set hardware configuration information.
> > > > > > The dma client drivers are not mainlined  yet and it is
> > > > > > Internally used by our git-tree  to test the DMA functionality
> > > > > > in
> > loopback .
> > > > >
> > > > > I would suggest you add the test driver into the main dmaengine
> > > > > driver file directly then, so you don't need to export the symbols.
> > > > > If there are important reasons to keep that as separate files,
> > > > > just move the header to the drivers/dma/ directory and add the
> > > > > test driver
> > > there.
> > > >
> > > > Sorry I forgot to mention the below things in the mail .The Config
> > > > API's and structures not only used by the dmaengine driver's but
> > > > also used by the  various IP's  (Ex: Ethernet driver and SRIO
> > > > driver these drivers are under development).For example the
> > > > Ethernet driver is resides under drivers/net/ethernet but it needs
> > > > to set some specific configuration parameters of the dma that's
> > > > why created a separate header file for the h/w configurable
> parameters.
> > >
> > > That is a bug in the ethernet driver, and we should not merge such code.
> > >
> > > Please fix those drivers before submitting them, so they don't rely
> > > on additional interfaces beyond what the DMA engine API provides.
> > >
> > > If you need something that the common interface is missing, you can
> > > send a patch to extend the dmaengine core driver, but more likely it
> > > already does what you need and you are just not using it right.
> > >
> >
> > Sorry for the delay in the reply.
> > We need that header file in the include/linux/ directory for various
> > reasons.
> >
> >  As you know the Xilinx DMA's have a set of configurable parameters
> > which we expect the DMA users to take advantage of.
> >
> >  For example:
> >  For Axi DMA we have the following parameters that we expect to be
> > commonly used.
> >  Coalesce count --> Used to configure the coalesce value.
> >  Delay timer ---> Used to set the delay value.
> >
> >  We expect the Xilinx AXI Ethernet driver to use the Axi DMA driver in
> > near furture. If so, using ethtool, we expect the driver users to play
> > with the above parameters to do performance tuning.
> >
> >  Hence AxiDMA driver must expose means to change coalese count or
> > delay timer.
> >
> >  Similarly For Axi VDMA we have the following parameters that will be
> > used by the users of this driver.
> >  hsize  --> Used to configure number of bytes per line.
> >  vsize  -->Number of lines per frame.
> >  stride  --> Number of bytes per line.
> >
> >
> >  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.
>
> Ping ?
>
> Regards,
> Kedar.
>
> >
> > Regards,
> > Kedar.
> >
> > >   Arnd



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