netdev - Re: [PATCH net-next v7 6/9] net: txgbe: Support GPIO to SFP socket

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Message-ID: <2b8a8ef8-b98b-42f7-b91d-2a9b05973d57@lunn.ch>
Date: Fri, 12 May 2023 16:20:38 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Jiawen Wu <jiawenwu@...stnetic.com>
Cc: netdev@...r.kernel.org, jarkko.nikula@...ux.intel.com,
	andriy.shevchenko@...ux.intel.com, mika.westerberg@...ux.intel.com,
	jsd@...ihalf.com, Jose.Abreu@...opsys.com, hkallweit1@...il.com,
	linux@...linux.org.uk, linux-i2c@...r.kernel.org,
	linux-gpio@...r.kernel.org, mengyuanlou@...-swift.com
Subject: Re: [PATCH net-next v7 6/9] net: txgbe: Support GPIO to SFP socket

> > Is that a hardware requirement, that interrupts only work when the interface is
> > running? Interrupts are not normally conditional like this, at least when the SoC
> > provides the GPIO controller.
> 
> Should we handle the interrupts when interface is not running?

You are adding a generic GPIO controller. It could in theory be used
for anything. GPIO controlled LEDs, buttons, bit-banging MDIO/SPI/I2C,
etc. I would not artificially limit interrupts to just when the
interface is up, unless you need to.

You should also take a look at the SFP code. When does it enable
interrupts? When the SFP device is created, or when phylink_start() is
called? SoC GPIO controllers work all the time, so it could be the SFP
code just assumes interrupts work as soon as the GPIO is
available. With the interface down, try disconnecting/connecting the
fibre and see if /sys/kernel/debug/sfpX/state shows it sees LOS
change.

     Andrew