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

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Date: Mon, 22 May 2023 18:58:19 +0800
From: Jiawen Wu <jiawenwu@...stnetic.com>
To: "'Andrew Lunn'" <andrew@...n.ch>,
	"'Michael Walle'" <michael@...le.cc>,
	"'Shreeya Patel'" <shreeya.patel@...labora.com>
Cc: "'Andy Shevchenko'" <andy.shevchenko@...il.com>,
	<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 v8 6/9] net: txgbe: Support GPIO to SFP socket

On Monday, May 22, 2023 5:01 PM, Jiawen Wu wrote:
> On Friday, May 19, 2023 9:13 PM, Andrew Lunn wrote:
> > > 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.
> >
> > So you have another interrupt controller above the GPIO interrupt
> > controller. regmap-gpio is pushing you towards describing this
> > interrupt controller as a Linux interrupt controller.
> >
> > When you look at drivers handling interrupts, most leaf interrupt
> > controllers are not described as Linux interrupt controllers. The
> > driver interrupt handler reads the interrupt status register and
> > internally dispatches to the needed handler. This works well when
> > everything is internal to one driver.
> >
> > However, here, you have two drivers involved, your MAC driver and a
> > GPIO driver instantiated by the MAC driver. So i think you are going
> > to need to described the MAC interrupt controller as a Linux interrupt
> > controller.
> >
> > Take a look at the mv88e6xxx driver, which does this. It has two
> > interrupt controller embedded within it, and they are chained.
> 
> Now I add two interrupt controllers, the first one for the MAC interrupt,
> and the second one for regmap-gpio. In the second adding flow,
> 
> 	irq = irq_find_mapping(txgbe->misc.domain, TXGBE_PX_MISC_GPIO_OFFSET);
> 	err = regmap_add_irq_chip_fwnode(fwnode, regmap, irq, 0, 0,
> 					 chip, &chip_data);
> 
> and then,
> 
> 	config.irq_domain = regmap_irq_get_domain(chip_data);
> 	gpio_regmap = gpio_regmap_register(&config);
> 
> "txgbe->misc.domain" is the MAC interrupt domain. I think this flow should
> be correct, but still failed to get gpio_irq from gpio_desc with err -517.
> 
> And I still have doubts about what I said earlier:
> https://lore.kernel.org/netdev/20230515063200.301026-1-
> jiawenwu@...stnetic.com/T/#me1be68e1a1e44426ecc0dd8edf0f6b224e50630d
> 
> There really is nothing wrong with gpiochip_to_irq()??

There is indeed something wrong in gpiochip_to_irq(), since commit 5467801 ("gpio:
Restrict usage of GPIO chip irq members before initialization"):
https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit?id=5467801f1fcbdc46bc7298a84dbf3ca1ff2a7320

When I use gpio_regmap_register() to add gpiochip, gpiochip_add_irqchip() will just
return 0 since irqchip = NULL, then gc->irq.initialized = false.

 Cc the committer: Shreeya Patel.