[PATCH v6 1/2] dmaengine: Add Xilinx Central DMA DT Binding Documentation

[PATCH v6 1/2] dmaengine: Add Xilinx Central DMA DT Binding Documentation

[Kedareswara rao Appana]

Device-tree binding documentation of Xilinx Central DMA Engine.

Signed-off-by: Kedareswara rao Appana <appanad@xilinx.com>
---
Changes in v6:
- None.
Changes in v5:
- None.
Changes in v4:
- None.
Changes in v3:
- Used proper alignment for all the properties.
Changes in v2:
- Change property 'xlnx,data-width' to 'xlnx,datawidth' in the description
  to match the implementation.

 .../devicetree/bindings/dma/xilinx/xilinx_cdma.txt | 54 ++++++++++++++++++++++
 1 file changed, 54 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/dma/xilinx/xilinx_cdma.txt

diff --git a/Documentation/devicetree/bindings/dma/xilinx/xilinx_cdma.txt b/Documentation/devicetree/bindings/dma/xilinx/xilinx_cdma.txt
new file mode 100644
index 0000000..8b366ce
--- /dev/null
+++ b/Documentation/devicetree/bindings/dma/xilinx/xilinx_cdma.txt
@@ -0,0 +1,54 @@
+Xilinx AXI CDMA engine, it does transfers between memory-mapped source
+address and a memory-mapped destination address.
+
+Required properties:
+- compatible		: Should be "xlnx,axi-cdma-1.00.a"
+- #dma-cells		: Should be <1>, see "dmas" property below
+- reg			: Should contain cdma registers location and length.
+- dma-channel child node: Should have only one channel
+
+Optional properties:
+- xlnx,include-sg	: Tells whether configured for Scatter-mode in
+			  the hardware.
+
+Required child node properties:
+- compatible		: It should be "xlnx,axi-cdma-channel".
+- interrupts		: Should contain per channel CDMA interrupts.
+- xlnx,datawidth	: Should contain the stream data width, take values
+			  {32,64...1024}.
+
+Option child node properties:
+- xlnx,include-dre	: Tells whether hardware is configured for Data
+			  Realignment Engine.
+
+Example:
+++++++++
+
+axi_cdma_0: axicdma@7e200000 {
+       compatible = "xlnx,axi-cdma-1.00.a";
+       #dma-cells = <1>;
+       reg = < 0x7e200000 0x10000 >;
+       dma-channel@7e200000 {
+               compatible = "xlnx,axi-cdma-channel";
+               interrupts = < 0 55 4 >;
+               xlnx,datawidth = <0x40>;
+       } ;
+} ;
+
+
+* DMA client
+
+Required properties:
+- dmas		: a list of <[Central DMA device phandle] [Channel ID]> pairs,
+		  where Channel ID is '0' for write/tx and '1' for read/rx
+                  channel.
+- dma-names	: a list of DMA channel names, one per "dmas" entry
+
+Example:
+++++++++
+
+cdmatest_0: cdmatest@0 {
+       compatible ="xlnx,axi-cdma-test-1.00.a";
+       dmas = <&axi_cdma_0 0>;
+       dma-names = "cdma";
+} ;
-- 
2.1.2

Re: [PATCH v6 1/2] dmaengine: Add Xilinx Central DMA DT Binding Documentation

[Arnd Bergmann]

On Monday 07 September 2015 18:03:08 Kedareswara rao Appana wrote:
> +- dma-channel child node: Should have only one channel
> 

What is the point of the child node if there is only one instance?

Could you just fold this into the main node instead?

(Sorry jumping in here without looking at the previous versions, I
just returned to work from my parental leave).

	Arnd
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RE: [PATCH v6 1/2] dmaengine: Add Xilinx Central DMA DT Binding Documentation

[Appana Durga Kedareswara Rao]

Hi Arnd,
	
> -----Original Message-----
> From: Arnd Bergmann [mailto:arnd@arndb.de]
> Sent: Monday, September 07, 2015 6:26 PM
> To: Appana Durga Kedareswara Rao
> Cc: robh+dt@kernel.org; vinod.koul@intel.com; Anirudha Sarangi;
> pawel.moll@arm.com; mark.rutland@arm.com; ijc+devicetree@hellion.org.uk;
> galak@codeaurora.org; Michal Simek; Soren Brinkmann; Appana Durga
> Kedareswara Rao; devicetree@vger.kernel.org; linux-arm-
> kernel@lists.infradead.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH v6 1/2] dmaengine: Add Xilinx Central DMA DT Binding
> Documentation
> 
> On Monday 07 September 2015 18:03:08 Kedareswara rao Appana wrote:
> > +- dma-channel child node: Should have only one channel
> >
> 
> What is the point of the child node if there is only one instance?

Sorry for the delay in reply I was on leave for the last couple weeks.

There are few reasons for these:
---> We (Xilinx) have 3 different DMA's and in order to make consistency b/w the three dma's used the child node concepts so that users can easily compare the drivers
---> It is a soft IP so features like (multiple channels, cyclic dma mode) may added in nearby future so for future driver changes it will be straight forward. 

Please let me know if it is wrong will fix it and will send the next version of the path.

Regards,
Kedar.

> 
> Could you just fold this into the main node instead?
> 
> (Sorry jumping in here without looking at the previous versions, I just returned to
> work from my parental leave).
> 
> 	Arnd