Hi Lars,
Thanks for the review...
> -----Original Message-----
> From: Lars-Peter Clausen [mailto:[email protected]]
> Sent: Wednesday, April 27, 2016 6:10 PM
> To: Appana Durga Kedareswara Rao <[email protected]>;
> [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]; Michal Simek
> <[email protected]>; Soren Brinkmann <[email protected]>;
> [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]; Anirudha
> Sarangi <[email protected]>; Punnaiah Choudary Kalluri
> <[email protected]>
> Cc: [email protected]; [email protected]; linux-
> [email protected]; [email protected]
> Subject: Re: [PATCH v7 1/2] Documentation: DT: dma: Add Xilinx zynqmp dma
> device tree binding documentation
>
> On 04/27/2016 09:33 AM, Appana Durga Kedareswara Rao wrote:
> > Hi Lars,
> >
> >> -----Original Message-----
> >> From: Lars-Peter Clausen [mailto:[email protected]]
> >> Sent: Wednesday, April 27, 2016 12:42 PM
> >> To: Appana Durga Kedareswara Rao <[email protected]>;
> >> [email protected]; [email protected]; [email protected];
> >> [email protected]; [email protected]; Michal Simek
> >> <[email protected]>; Soren Brinkmann <[email protected]>;
> >> [email protected]; [email protected]; Appana Durga
> >> Kedareswara Rao <[email protected]>; [email protected];
> >> [email protected]; [email protected]; Anirudha
> >> Sarangi <[email protected]>; Punnaiah Choudary Kalluri
> >> <[email protected]>
> >> Cc: [email protected]; [email protected];
> >> linux- [email protected]; [email protected]
> >> Subject: Re: [PATCH v7 1/2] Documentation: DT: dma: Add Xilinx zynqmp
> >> dma device tree binding documentation
> >>
> >> On 04/27/2016 09:05 AM, Kedareswara rao Appana wrote:
> >> [...]
> >>> +- xlnx,include-sg : Indicates the controller to operate in simple
> >>> or
> >>> + scatter gather dma mode
> >>> +- xlnx,ratectrl : Scheduling interval in terms of clock cycles
> >>> for
> >>> + source AXI transaction
> >>> +- xlnx,overfetch : Tells whether the channel is allowed to over
> >>> + fetch the data
> >>> +- xlnx,src-issue : Number of AXI outstanding transactions on source
> >> side
> >>> +- xlnx,src-burst-len : AXI length for data read. Support only power
> >>> of
> >>> + 2 byte values.
> >>> +- xlnx,dst-burst-len : AXI length for data write. Support only power
> >>> of
> >>
> >> These are all software runtime configuration parameters that you'd
> >> want to change at runtime depending on which peripheral you are
> >> targeting with a specific DMA transfer. These really do not belong into the
> devicetree.
> >
> > You mean to have a separate config structure in the driver and handle
> > the above parameters Through that structure???
> >
> > I understand that above will work for slave dma transfer types what
> > about memory to memory Transfers where we don't have provision to the use
> this parameters...
>
> These parameters are just as application specific as e.g. the DMA
> source/destination address or the DMA transfer length. If you want to use the
> DMA controller in a different configuration you'd have to re-compile the DTB
> and reboot your board, that is not really practical. Especially considering
> that
> you'd typically have multiple applications using the DMA controller in
> different
> configurations concurrently. In general if I have to reconfigure the DT
> depending
> on what application software is running something is fundamentally broken.
>
> Derive these parameters at runtime depending on the requested transfer. E.g.
> some transfer types only work in SG mode, others only work in non-SG modes.
> For those which can work in both modes choose the one that is more efficient.
> Similar for the other parameters.
Ok will fix in the next version...
Will use module_params for the above properties.
Regards,
Kedar.
>
> - Lars
