Re: [RFC Patch net-next v2] net: dsa: microchip: lan937x: enable interrupt for internal phy link detection

Andrew Lunn
2022-08-23T16:47:55Z

> I used the same gpio line number of switch as the interrupt for
> internal phy. And when phy link up/down happens, it triggers both the
> switch and phy interrupt routine.

Ah, shared interrupt. O.K.

> I have not used irq_domain before. Can you please brief on how phy
> interrupt handler is called from chip.c & global2.

There are two different ways this can all be glued together.

Using irq_domain, each interrupt source becomes a full interrupt in
Linux. You can see these individual interrupt sources in
/proc/interrupts. You can use request_threaded_irq() on it. The
mv88e6xxx driver is also an interrupt controller as well as an
Ethernet switch.

> The dts file I used for testing,
> spi1: spi@f8008000 {
> cs-gpios = <0>, <0>, <0>, <&pioC 28 0>;
> id = <1>;
> status = "okay";
>
> lan9370: lan9370@3 {
> compatible = "microchip,lan9370";
> reg = <3>;
> spi-max-frequency = <44000000>;
> interrupt-parent = <&pioB>;
> interrupts = <28 IRQ_TYPE_LEVEL_LOW>;
> interrupt-controller;
> status = "okay";
> ports {
> #address-cells = <1>;
> #size-cells = <0>;
> port@0 {
> reg = <0x0>;
> phy-handle = <&t1phy0>;
> phy-mode = "internal";
> label = "lan1";
> };
> port@1 {
> reg = <0x1>;
> phy-handle = <&t1phy1>;
> phy-mode = "internal";
> label = "lan2";
> };
> }
> }
>
> mdio {
> #address-cells = <1>;
> #size-cells = <0>;
> compatible = "microchip,lan937x-mdio";
>
> t1phy0: ethernet-phy@0{
> interrupt-parent = <&lan9370>;
> interrupts = <28 IRQ_TYPE_LEVEL_LOW>;

So here you would use the interrupt number within the domain. Ideally
you want port 0 to use interrupt 0.

> reg = <0x0>;
> };
> t1phy1: ethernet-phy@1{
> interrupt-parent = <&lan9370>;
> interrupts = <28 IRQ_TYPE_LEVEL_LOW>;

and here port 1 uses interrupt 1.

> reg = <0x1>;
> };
> }
> }

You can see this for an Marvell switch here:

https://elixir.bootlin.com/linux/latest/source/arch/arm/boot/dts/vf610-zii-dev-rev-b.dts#L93

Doing it this way is however very verbose. I later discovered a short
cut:

https://elixir.bootlin.com/linux/latest/source/drivers/net/dsa/mv88e6xxx/global2.c#L1164

by setting mdiobus->irq[] to the interrupt number, phylib will
automatically use the correct interrupt without needing an DT.

Andrew