On 2017-07-17 12:52, Boris Brezillon wrote:
On Mon, 17 Jul 2017 11:41:01 +0530 Abhishek Sahu <[email protected]> wrote:>> > + >> > +nand@79b0000 { > > nand-controller@xxxx { > > BTW, glad to see another driver moving to the new DT representation > :-). > >> > + compatible = "qcom,qpic-nandc-v1.4.0"; >> > + reg = <0x79b0000 0x1000>; >> > + >> > + clocks = <&gcc GCC_QPIC_CLK>, >> > + <&gcc GCC_QPIC_AHB_CLK>; >> > + clock-names = "core", "aon"; >> > + >> > + #address-cells = <1>; >> > + #size-cells = <0>; >> > + >> > + nandcs@0 { > > nand@0 { > >> > + compatible = "qcom,nandcs"; > > Why do you need a compatible here? It is the part of original driver. We can connect multiple NAND devices in the same bus and qcom,nandcs is being used for each connected NAND device. Each NAND device can use different chip select, ecc strength etc which we can specify under this sub node.Still don't understand why you need a compatible? Is this a memory bus where you can connect other kind of memories (parallel NORs, SRAMs, ...)? If that's not the case, then considering all subnodes of the nand-controller node containing a reg property as NAND devices is fine, you don't need this compatible = "nand,cs" (see sunxi-nand bindings [1]).
Thanks Boris for giving detailed references. We can connect other parallel devices also but we have different hardware wrappers over generic EBI2/QPIC which will MUX/arbitrate the device access from the hardware itself. So this NAND driver will only control multiple NAND devices. We can remove this compatible and use the bindings similar to sunxi-nand. I will do the required changes and will post in v2 of the same patch series.
If the bus is generic and can be attached non-NAND devices, I'd recommend looking at atmel's binding [2], because you're likely to have one instance of the NAND controller logic for all NAND devices connected on this bus. And more importantly, if the bus a generic, the node should not be named nand or nand-controller, and the compatible should not contain 'nandc' in it. [1]http://elixir.free-electrons.com/linux/latest/source/Documentation/devicetree/bindings/mtd/sunxi-nand.txt#L34 [2]http://elixir.free-electrons.com/linux/latest/source/Documentation/devicetree/bindings/mtd/atmel-nand.txt#L70
-- Abhishek Sahu
