Re: [PATCH v3 1/3] nvmem: Update the OF binding to use a subnode for the cells list

[Srinivas Kandagatla]

On 18/04/18 12:41, Alban wrote:
> On Tue, 17 Apr 2018 18:00:40 +0200
> Alban <albeu@xxxxxxx> wrote:
>
> > On Tue, 17 Apr 2018 16:44:01 +0100
> > Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx> wrote:
> >
> > > Thanks for explaining,
> > >
> > > On 17/04/18 15:54, Alban wrote:
> > > > This will not only allow reading the calibration data from nvmem, but
> > > > will also create a partition on the MTD device, which is not acceptable.
> > > > With my proposed binding this would become:
> > > >
> > > > flash@0 {
> > > > 	#address-cells = <1>;
> > > > 	#size-cells = <1>;
> > > > 	compatible = "s25sl064a";
> > > > 	reg = <0>;
> > > >
> > > > 	nvmem-cells {
> > > > 		compatible = "nvmem-cells";
> > > > 		#address-cells = <1>;
> > > > 		#address-cells = <1>;
> > > >
> > > > 		calibration: calib@404 {
> > > > 			reg = <0x404 0x10>;
> > > > 		};
> > > > 	};
> > >
> > > Why can't we make nvmem-cells node a nvmem provider in this case?
> > > Which should work!
> >
> > TBH I just copied what have been done to fix the same problem with the
> > MTD partitions. But yes we could also just extend the current binding
> > to require a compatible string on each nvmem-cell, which would not
> > require any code change to support.
>
> However this scheme will not work if the device node binding already
> have subnodes with addresses. The addressing, as specified by
> #address-cells and #size-cells, might be incompatible or might overlap.
> Using the nvmem-cells subnode solve this problem.

I was also suggesting you to use nvmem-cell subnode, but make it a 
proper nvmem provider device, rather than reusing its parent device.

You would end up some thing like this in dt.

flash@0 {
	#address-cells = <1>;
	#size-cells = <1>;
	compatible = "s25sl064a";
	reg = <0>;

	nvmem-cells {
		compatible = "mtd-nvmem";
		#address-cells = <1>;
		#size-cells = <1>;

		calibration: calib@404 {
			reg = <0x404 0x10>;
		};
	};
};

--srini

> Alban