RE: [PATCH net-next v8 6/9] net: txgbe: Support GPIO to SFP socket

["Jiawen Wu" <jiawenwu@trustnetic.com>]

> -----Original Message-----
> From: Andrew Lunn <andrew@lunn.ch>
> Sent: Thursday, May 18, 2023 8:49 PM
> To: Jiawen Wu <jiawenwu@trustnetic.com>
> Cc: 'Andy Shevchenko' <andy.shevchenko@gmail.com>; netdev@vger.kernel.org; jarkko.nikula@linux.intel.com;
> andriy.shevchenko@linux.intel.com; mika.westerberg@linux.intel.com; jsd@semihalf.com; Jose.Abreu@synopsys.com;
> hkallweit1@gmail.com; linux@armlinux.org.uk; linux-i2c@vger.kernel.org; linux-gpio@vger.kernel.org; mengyuanlou@net-swift.com
> Subject: Re: [PATCH net-next v8 6/9] net: txgbe: Support GPIO to SFP socket
> 
> > > I _think_ you are mixing upstream IRQs and downstream IRQs.
> > >
> > > Interrupts are arranged in trees. The CPU itself only has one or two
> > > interrupts. e.g. for ARM you have FIQ and IRQ. When the CPU gets an
> > > interrupt, you look in the interrupt controller to see what external
> > > or internal interrupt triggered the CPU interrupt. And that interrupt
> > > controller might indicate the interrupt came from another interrupt
> > > controller. Hence the tree structure. And each node in the tree is
> > > considered an interrupt domain.
> > >
> > > A GPIO controller can also be an interrupt controller. It has an
> > > upstream interrupt, going to the controller above it. And it has
> > > downstream interrupts, the GPIO lines coming into it which can cause
> > > an interrupt. And the GPIO interrupt controller is a domain.
> > >
> > > So what exactly does gpio_regmap_config.irq_domain mean? Is it the
> > > domain of the upstream interrupt controller? Is it an empty domain
> > > structure to be used by the GPIO interrupt controller? It is very
> > > unlikely to have anything to do with the SFP devices below it.
> >
> > Sorry, since I don't know much about interrupt,  it is difficult to understand
> > regmap-irq in a short time. There are many questions about regmap-irq.
> >
> > When I want to add an IRQ chip for regmap, for the further irq_domain,
> > I need to pass a parameter of IRQ, and this IRQ will be requested with handler:
> > regmap_irq_thread(). Which IRQ does it mean?
> 
> That is your upstream IRQ, the interrupt indicating one of your GPIO
> lines has changed state.
> 
> > In the previous code of using
> > devm_gpiochip_add_data(), I set the MSI-X interrupt as gpio-irq's parent, but
> > it was used to set chained handler only. Should the parent be this IRQ? I found
> > the error with irq_free_descs and irq_domain_remove when I remove txgbe.ko.
> 
> Do you have one MSI-X dedicated for GPIOs. Or is it your general MAC
> interrupt, and you need to read an interrupt controller register to
> determine it was GPIOs which triggered the interrupt?

I have one MSI-X interrupt for all general MAC interrupt (see TXGBE_PX_MISC_IEN_MASK).
It has 32 bits to indicate various interrupts, GPIOs are the one of them. When GPIO
interrupt is determined, GPIO_INT_STATUS register should be read to determine
which GPIO line has changed state.

> If you are getting errors when removing the driver it means you are
> missing some level of undoing what us done in probe. Are you sure
> regmap_del_irq_chip() is being called on unload?

I used devm_* all when I registered them.

> > As you said, the interrupt of each tree node has its domain. Can I understand
> > that there are two layer in the interrupt tree for MSI-X and GPIOs, and requesting
> > them separately is not conflicting? Although I thought so, but after I implement
> > gpio-regmap, SFP driver even could not find gpio_desc. Maybe I missed something
> > on registering gpio-regmap...
> 
> That is probably some sort of naming issue. You might want to add some
> prints in swnode_find_gpio() and gpiochip_find() to see what it is
> looking for vs what the name actually is.

Thanks for the advice, I'll try again today.