Re: FDT syscon driver

[Jared McNeill <jmcneill%invisible.ca@localhost>]

We're only really concerned with mainline dts files. Ignore anything you 
see in the vendor tree.

Check out the binding docs for this device if you haven't already:

https://www.kernel.org/doc/Documentation/devicetree/bindings/net/meson-dwmac.txt

There are no syscons defined, instead they give you the second address 
range in the reg property:

- reg:	The first register range should be the one of the DWMAC
	controller. The second range is is for the Amlogic specific
	configuration (for example the PRG_ETHERNET register range
	on Meson8b and newer)

Since fdtbus_get_reg takes an index parameter, you can look this up and 
map it yourself. The binding spec matches what I see in the dts:

https://nxr.netbsd.org/xref/src/sys/external/gpl2/dts/dist/arch/arm64/boot/dts/amlogic/meson-gx.dtsi#444

Is there another register range you need to access?

Cheers,
Jared


On Sun, 1 Jul 2018, Robert Swindells wrote:

> Jared McNeill <jmcneill%invisible.ca@localhost> wrote:
> > On Sun, 1 Jul 2018, Robert Swindells wrote:
> > > Jared McNeill <jmcneill%invisible.ca@localhost> wrote:
> > > > How to access it is dictated by the binding spec for your device. You need
> > > > some way to find the phandle. Two methods I have encountered:
> > >
> > > [snip]
> > >
> > > The Odroid C2 doesn't use either of them, there are no cross references
> > > and the devices are at the same level in the tree.
> >
> > Can you point me to an example?
>
> The ethernet controller has two registers within the page at 0xc8834000
>
> 		periphs@c8834000 {
> 			compatible = "simple-bus";
> 			reg = <0x00000000 0xc8834000 0x00000000 0x00002000>;
> 			#address-cells = <0x00000002>;
> 			#size-cells = <0x00000002>;
> 			ranges = <0x00000000 0x00000000 0x00000000 0xc8834000 0x00000000 0x00002000>;
>
>
> 		ethernet@c9410000 {
> 			compatible = "amlogic,meson-gx-dwmac", "amlogic,meson-gx
> bb-dwmac", "snps,dwmac";
> 			reg = <0x00000000 0xc9410000 0x00000000 0x00010000 0x00000000 0xc8834540 0x00000000 0x00000004>;
> 			interrupts = <0x00000000 0x00000008 0x00000001>;
> 			interrupt-names = "macirq";
> 			status = "okay";
> 			clocks = <0x0000000c 0x00000024 0x0000000c 0x00000004 0x0000000c 0x0000000f>;
> 			clock-names = "stmmaceth", "clkin0", "clkin1";
> 			pinctrl-0 = <0x00000018>;
> 			pinctrl-names = "default";
> 			phy-handle = <0x00000019>;
> 			phy-mode = "rgmii";
> 			snps,reset-gpio = <0x0000001a 0x0000000e 0x00000000>;
> 			snps,reset-delays-us = <0x00000000 0x00002710 0x000f4240>;
> 			snps,reset-active-low;
> 			amlogic,tx-delay-ns = <0x00000002>;
>
> There are other things within the same page:
>
> 			rng {
> 				compatible = "amlogic,meson-rng";
> 				reg = <0x00000000 0x00000000 0x00000000 0x00000004>;
> 				clocks = <0x0000000c 0x00000019>;
> 				clock-names = "core";
> 			};
> 			pinctrl@4b0 {
> 				compatible = "amlogic,meson-gxbb-periphs-pinctrl";
>                                ...
>
> The device tree from Hardkernel's kernel is different again to the
> mainline one:
>
> 	gpiomem {
> 		compatible = "amlogic,meson-gpiomem";
> 		reg = <0x0 0xc8834000 0x0 0x1000>;
> 		status = "okay";
> 	};
>
> 	ethmac: ethernet@0xc9410000{
> 		compatible = "amlogic, gxbb-rgmii-dwmac";
> 		reg = <0x0 0xc9410000 0x0 0x10000
> 		0x0 0xc8834540 0x0 0x8>;
> 		interrupts = <0 8 1>;
> 		phy-mode= "rgmii";
> 		pinctrl-names = "eth_pins";
> 		pinctrl-0 = <&eth_pins>;
> 		rst_pin-gpios = <&gpio GPIOZ_14 0>;
> 		mc_val = <0x1621>;
> 		resets = <&clock GCLK_IDX_ETHERNET>;
> 		reset-names = "ethpower";
> 		interrupt-names = "macirq";
> 		clocks = <&clock CLK_81>;
> 		clock-names = "ethclk81";
> 		 max-frame-size = <3582>;