RE: [LINUX PATCH v10 1/2] dt-bindings: mtd: arasan: Add device tree binding documentation

[Naga Sureshkumar Relli <nagasure@xilinx.com>]

Hi Boris,

> -----Original Message-----
> From: Boris Brezillon [mailto:boris.brezillon@bootlin.com]
> Sent: Monday, August 20, 2018 6:03 PM
> To: Naga Sureshkumar Relli <nagasure@xilinx.com>
> Cc: miquel.raynal@bootlin.com; richard@nod.at; dwmw2@infradead.org;
> computersforpeace@gmail.com; marek.vasut@gmail.com; kyungmin.park@samsung.com;
> absahu@codeaurora.org; peterpandong@micron.com; frieder.schrempf@exceet.de; linux-
> mtd@lists.infradead.org; linux-kernel@vger.kernel.org; Michal Simek <michals@xilinx.com>;
> nagasureshkumarrelli@gmail.com
> Subject: Re: [LINUX PATCH v10 1/2] dt-bindings: mtd: arasan: Add device tree binding
> documentation
> 
> On Fri, 17 Aug 2018 18:49:23 +0530
> Naga Sureshkumar Relli <naga.sureshkumar.relli@xilinx.com> wrote:
> 
> > This patch adds the dts binding document for arasan nand flash
> > controller.
> >
> > Signed-off-by: Naga Sureshkumar Relli
> > <naga.sureshkumar.relli@xilinx.com>
> > ---
> > Changes in v10:
> > - None
> > Changes in v9:
> > - None
> > Changes in v8:
> > - Updated compatible and clock-names as per Boris comments Changes in
> > v7:
> > - Corrected the acronyms those should be in caps changes in v6:
> > - Removed num-cs property
> > - Separated nandchip from nand controller changes in v5:
> > - None
> > Changes in v4:
> > - Added num-cs property
> > - Added clock support
> > Changes in v3:
> > - None
> > Changes in v2:
> > - None
> > ---
> >  .../devicetree/bindings/mtd/arasan_nand.txt        | 38 ++++++++++++++++++++++
> >  1 file changed, 38 insertions(+)
> >  create mode 100644
> > Documentation/devicetree/bindings/mtd/arasan_nand.txt
> >
> > diff --git a/Documentation/devicetree/bindings/mtd/arasan_nand.txt
> > b/Documentation/devicetree/bindings/mtd/arasan_nand.txt
> > new file mode 100644
> > index 0000000..234d7ca
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/mtd/arasan_nand.txt
> > @@ -0,0 +1,38 @@
> > +Arasan NAND Flash Controller with ONFI 3.1 support
> > +
> > +Required properties:
> > +- compatible:		Should be "xlnx,zynqmp-nand" or "arasan,nfc-v3p10"
> 
> In your example it's not an "or" since both are defined.
In our previous discussion (https://lore.kernel.org/patchwork/patch/748901/)
We decided to have compatible strings like " compatible = "<soc-vendor>,<ip-revision>", "arasan,<ip-revision>";"
So it should be either of these.
so I will write something like below
"Possible values are  "xlnx,zynqmp-nand" 
			"arasan,nfc-v3p10"
And in example I will mention any one compatible.
Is it ok?
> 
> > +- reg:			Memory map for module access
> > +- interrupt-parent:	Interrupt controller the interrupt is routed through
> > +- interrupts:		Should contain the interrupt for the device
> > +- clock-name:		List of input clocks - "sys", "flash"
> 
>      clock-names
Ok, will correct it in next version.
> 
> > +			(See clock bindings for details)
> > +- clocks:		Clock phandles (see clock bindings for details)
> > +
> > +Optional properties:
> > +- arasan,has-mdma: Enables DMA support
> 
> Can't you detect that based on the compatible (or thanks to a register). If it's something you
> choose when configuring the IP and can't detect at runtime I guess it's fine.
There is no way to select DMA when configuring the IP.
But it has internal DMA and there is a register to select PIO or DMA while starting a transfer.
So if user really don't want DMA, then we will never set DMA in the code based on DT property.
> 
> > +
> > +For NAND partition information please refer the below file
> > +Documentation/devicetree/bindings/mtd/partition.txt
> > +
> > +Example:
> > +	nand0: nand@ff100000 {
> > +		compatible = "xlnx,zynqmp-nand", "arasan,nfc-v3p10"
> > +		reg = <0x0 0xff100000 0x1000>;
> > +		clock-name = "sys", "flash"
> > +		clocks = <&misc_clk &misc_clk>;
> > +		interrupt-parent = <&gic>;
> > +		interrupts = <0 14 4>;
> > +		arasan,has-mdma;
> > +		#address-cells = <1>;
> > +		#size-cells = <0>
> > +
> > +		nand@0 {
> > +			reg = <0>
> > +			partition@0 {
> > +				label = "filesystem";
> > +				reg = <0x0 0x0 0x1000000>;
> > +			};
> 
> Hm, not sure you need to define partitions in this example, but if you do, please define your
> partitions in a 'partitions' subnode:
> 
> 			partitions {
> 				compatible = "fixed-partitions";
> 				#address-cells = <1>;
> 				#size-cells = <1>;
> 
> 				partition@0 {
> 					reg = <0x0 0x1000000>;
> 					...
> 				};
> 				...
> 			};
> 
> > +			(...)
Ok, just now I saw Documentation/devicetree/bindings/mtd/marvell-nand.txt, I will update it accordingly in  next version.
> > +		};
> > +	};


Thanks,
Naga Sureshkumar Relli.