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

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Date:   Tue, 23 Aug 2022 16:33:14 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Arun.Ramadoss@...rochip.com
Cc:     olteanv@...il.com, linux-kernel@...r.kernel.org,
        UNGLinuxDriver@...rochip.com, vivien.didelot@...il.com,
        linux@...linux.org.uk, Tristram.Ha@...rochip.com,
        f.fainelli@...il.com, kuba@...nel.org, edumazet@...gle.com,
        pabeni@...hat.com, netdev@...r.kernel.org,
        Woojung.Huh@...rochip.com, davem@...emloft.net
Subject: Re: [RFC Patch net-next v2] net: dsa: microchip: lan937x: enable
 interrupt for internal phy link detection

> 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@...08000 {
> 	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