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

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Date: Fri, 12 May 2023 14:38:15 +0800
From: Jiawen Wu <jiawenwu@...stnetic.com>
To: "'Andrew Lunn'" <andrew@...n.ch>
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

On Thursday, May 11, 2023 8:32 PM, Andrew Lunn wrote:
> > +static int txgbe_gpio_get(struct gpio_chip *chip, unsigned int
> > +offset) {
> > +	struct wx *wx = gpiochip_get_data(chip);
> > +	struct txgbe *txgbe = wx->priv;
> > +	int val;
> > +
> > +	val = rd32m(wx, WX_GPIO_EXT, BIT(offset));
> > +
> > +	txgbe->gpio_orig &= ~BIT(offset);
> > +	txgbe->gpio_orig |= val;
> > +
> > +	return !!(val & BIT(offset));
> > +}
> 
> > +static void txgbe_irq_handler(struct irq_desc *desc) {
> > +	struct irq_chip *chip = irq_desc_get_chip(desc);
> > +	struct wx *wx = irq_desc_get_handler_data(desc);
> > +	struct txgbe *txgbe = wx->priv;
> > +	irq_hw_number_t hwirq;
> > +	unsigned long gpioirq;
> > +	struct gpio_chip *gc;
> > +	u32 gpio;
> > +
> > +	chained_irq_enter(chip, desc);
> > +
> > +	gpioirq = rd32(wx, WX_GPIO_INTSTATUS);
> > +
> > +	/* workaround for hysteretic gpio interrupts */
> > +	gpio = rd32(wx, WX_GPIO_EXT);
> > +	if (!gpioirq)
> > +		gpioirq = txgbe->gpio_orig ^ gpio;
> 
> Please could you expand on the comment. Are you saying that
> WX_GPIO_INTSTATUS sometimes does not contain the GPIO which caused the
> interrupt? If so, you then compare the last gpio_get with the current value and
> assume that is what caused the interrupt?

Yes. Sometime there is a lag in WX_GPIO_INTSTATUS. When the GPIO interrupt
cause,  the GPIO state has been back to its previous state. So I added this
workaround to save some...but only if there are other interrupts at the same
time, i.e. txgbe_irq_handler() called.

But I will remove it in the next version, because I find a more accurate solution.

> 
> > +
> > +	gc = txgbe->gpio;
> > +	for_each_set_bit(hwirq, &gpioirq, gc->ngpio)
> > +		generic_handle_domain_irq(gc->irq.domain, hwirq);
> > +
> > +	chained_irq_exit(chip, desc);
> > +
> > +	/* unmask interrupt */
> > +	if (netif_running(wx->netdev))
> > +		wx_intr_enable(wx, TXGBE_INTR_MISC(wx));
> 
> 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?