netdev - 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 10:45:35 +0000
From:   <Arun.Ramadoss@...rochip.com>
To:     <andrew@...n.ch>
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

Hi Andrew,
Thanks for the comments

On Mon, 2022-08-22 at 15:12 +0200, Andrew Lunn wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you
> know the content is safe
> 
> On Mon, Aug 22, 2022 at 02:50:17PM +0530, Arun Ramadoss wrote:
> > This patch enables the interrupts for internal phy link detection
> > for
> > LAN937x. The interrupt enable bits are active low. It first enables
> > port
> > interrupt and then port phy interrupt. Also patch register the irq
> > thread and in the ISR routine it clears the POR_READY_STS bit.
> > POR_READY_STS bit is write one clear bit and all other bit in the
> > register are read only. Since phy interrupts are handled by the
> > lan937x
> > phy layer, switch interrupt routine does not read the phy layer
> > interrupts.
> > +static irqreturn_t lan937x_switch_irq_thread(int irq, void
> > *dev_id)
> > +{
> > +     struct ksz_device *dev = dev_id;
> > +     irqreturn_t result = IRQ_NONE;
> > +     u32 data;
> > +     int ret;
> > +
> > +     /* Read global interrupt status register */
> > +     ret = ksz_read32(dev, REG_SW_INT_STATUS__4, &data);
> > +     if (ret)
> > +             return result;
> > +
> > +     if (data & POR_READY_INT) {
> > +             ret = ksz_write32(dev, REG_SW_INT_STATUS__4,
> > POR_READY_INT);
> > +             if (ret)
> > +                     return result;
> > +     }
> > +
> > +     return result;
> > +}
> 
> I don't understand how this all fits together. How do you get from
> this interrupt handler into the PHY interrupt handler?
> 
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. 
Earlier I tried to find out how to link switch port interrupt to phylib
but I could not get the logic. Only after reading your comment I come
to know phy interrupt can be triggered from the switch interrupt
handler. 
Today I went through the marvel implementation on interrupt handling
but could not grasp fully. (
https://lore.kernel.org/all/1476640613-25365-3-git-send-email-andrew@lunn.ch/T/#m74a139d43ca64833832d86810e2f4474277d7bf2
)
I have not used irq_domain before. Can you please brief on how phy
interrupt handler is called from chip.c & global2.

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>;
			reg = <0x0>;
		};
		t1phy1: ethernet-phy@1{
			interrupt-parent = <&lan9370>;
			interrupts = <28 IRQ_TYPE_LEVEL_LOW>;
			reg = <0x1>;
		};
	}
}

Is there anything, I need to change in the dts file.

> The hardware looks similar to the mv88e6xxx driver. You have a top
> level interrupt controller which indicates a port has some sort of
> interrupt handler. This is the mv88e6xxx_g1_irq_thread_work(). It
> finds which port triggered the interrupt and then hands the interrupt
> off to the nested interrupt handler.
> 
> mv88e6xxx_g2_irq_thread_fn() is the nested per port interrupt
> handler. It reads the per port interrupt status register, find the
> interrupt handler and calls the nested interrupt handler.
> 
> This all glues together because phylib does a request_threaded_irq()
> for the PHY interrupt, so this last nested interrupt handler is in
> phylib.
> 
>         Andrew