netdev - RE: [PATCH v3 1/2] gpio: mlxbf2: Introduce IRQ support

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Date:   Mon, 27 Sep 2021 14:04:07 +0000
From:   Asmaa Mnebhi <asmaa@...dia.com>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Andrew Lunn <andrew@...n.ch>
CC:     Andy Shevchenko <andy.shevchenko@...il.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        "David S. Miller" <davem@...emloft.net>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        David Thompson <davthompson@...dia.com>
Subject: RE: [PATCH v3 1/2] gpio: mlxbf2: Introduce IRQ support

> > +static int
> > +mlxbf2_gpio_irq_set_type(struct irq_data *irqd, unsigned int type) 
> > +{
> > +     struct gpio_chip *gc = irq_data_get_irq_chip_data(irqd);
> > +     struct mlxbf2_gpio_context *gs = gpiochip_get_data(gc);
> > +     int offset = irqd_to_hwirq(irqd);
> > +     unsigned long flags;
> > +     bool fall = false;
> > +     bool rise = false;
> > +     u32 val;
> > +
> > +     switch (type & IRQ_TYPE_SENSE_MASK) {
> > +     case IRQ_TYPE_EDGE_BOTH:
> > +     case IRQ_TYPE_LEVEL_MASK:
> > +             fall = true;
> > +             rise = true;
> > +             break;
> > +     case IRQ_TYPE_EDGE_RISING:
> > +     case IRQ_TYPE_LEVEL_HIGH:
> > +             rise = true;
> > +             break;
> > +     case IRQ_TYPE_EDGE_FALLING:
> > +     case IRQ_TYPE_LEVEL_LOW:
> > +             fall = true;
> > +             break;
> > +     default:
> > +             return -EINVAL;
> > +     }
>
> I'm still not convinced this is correct. Rising edge is different to 
> high. Rising edge only ever interrupts once, level keeps interrupting 
> until the source is cleared. You cannot store the four different 
> options in two bits.
>
> Linus, have you seen anything like this before?

> No, and I agree it looks weird.

> There must be some explanation, what does the datasheet say?

I have consulted the HW folks about this, and they confirmed that
Our internal GPIO HW detects the falling edge.
INT_N signal (KSZ9031) ---connected to---- > BlueField GPIO9 (or GPIO12)
Even if INT_N is an active level interrupt, the GPIO HW always detects
the falling edge. This is why the original signal doesn’t really matter.
The BlueField GPIO HW only support Edge interrupts.