RE: [PATCH] gpio: vf610: always set GPIO to input mode when used as interrupt source

[Bough Chen <haibo.chen@xxxxxxx>]

> -----Original Message-----
> From: Bough Chen
> Sent: 2024年4月24日 19:01
> To: 'Linus Walleij' <linus.walleij@xxxxxxxxxx>
> Cc: 'brgl@xxxxxxxx' <brgl@xxxxxxxx>; 'linux-gpio@xxxxxxxxxxxxxxx'
> <linux-gpio@xxxxxxxxxxxxxxx>; 'linux-kernel@xxxxxxxxxxxxxxx'
> <linux-kernel@xxxxxxxxxxxxxxx>; 'imx@xxxxxxxxxxxxxxx' <imx@xxxxxxxxxxxxxxx>
> Subject: RE: [PATCH] gpio: vf610: always set GPIO to input mode when used as
> interrupt source
> 
> > -----Original Message-----
> > From: Bough Chen
> > Sent: 2024年4月23日 20:21
> > To: Linus Walleij <linus.walleij@xxxxxxxxxx>
> > Cc: brgl@xxxxxxxx; linux-gpio@xxxxxxxxxxxxxxx;
> > linux-kernel@xxxxxxxxxxxxxxx; imx@xxxxxxxxxxxxxxx
> > Subject: RE: [PATCH] gpio: vf610: always set GPIO to input mode when
> > used as interrupt source
> >
> > > -----Original Message-----
> > > From: Linus Walleij <linus.walleij@xxxxxxxxxx>
> > > Sent: 2024年4月23日 19:41
> > > To: Bough Chen <haibo.chen@xxxxxxx>
> > > Cc: brgl@xxxxxxxx; linux-gpio@xxxxxxxxxxxxxxx;
> > > linux-kernel@xxxxxxxxxxxxxxx; imx@xxxxxxxxxxxxxxx
> > > Subject: Re: [PATCH] gpio: vf610: always set GPIO to input mode when
> > > used as interrupt source
> > >
> > > On Tue, Apr 23, 2024 at 4:28 AM <haibo.chen@xxxxxxx> wrote:
> > >
> > > > From: Haibo Chen <haibo.chen@xxxxxxx>
> > > >
> > > > Though the default pin configuration is INPUT, but if the prior
> > > > stage does configure the pins as OUTPUT, then Linux will not
> > > > reconfigure the pin as INPUT.
> > > >
> > > > e.g. When use one pin as interrupt source, and set as low level
> > > > trigger, if prior stage already set this pin as OUTPUT low, then
> > > > will meet interrupt storm.
> > > >
> > > > So always set GPIO to input mode when used as interrupt source to
> > > > fix above case.
> > > >
> > > > Signed-off-by: Haibo Chen <haibo.chen@xxxxxxx>
> > > > ---
> > > >  drivers/gpio/gpio-vf610.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/gpio/gpio-vf610.c b/drivers/gpio/gpio-vf610.c
> > > > index 07e5e6323e86..305b0bcdee6f 100644
> > > > --- a/drivers/gpio/gpio-vf610.c
> > > > +++ b/drivers/gpio/gpio-vf610.c
> > > > @@ -214,7 +214,7 @@ static int vf610_gpio_irq_set_type(struct
> > > > irq_data *d,
> > > u32 type)
> > > >         else
> > > >                 irq_set_handler_locked(d, handle_edge_irq);
> > > >
> > > > -       return 0;
> > > > +       return port->gc.direction_input(&port->gc, d->hwirq);
> > >
> > > Just call vf610_gpio_direction_input() instead of indirecting
> > > through
> > > gc->direction_input(), no need to jump through the vtable and as
> > > Bartosz says: it just makes that struct vulnerable.
> >
> > Thanks for your quick review, I will do that in V2.
> >
> > >
> > > Second:
> > >
> > > In this patch also implement gc->get_direction() which is currently
> > > unimplemented. If you are going to change the direction of a GPIO
> > > randomly at runtime then the framework really likes to have a chance
> > > to know the current direction for obvious reasons.
> >
> > Yes, will implement gc->get_direction(), if we did this before, then
> > for this case we meet, framework will print out error log, save much debug
> time.
> 
> Hi Linus,
> 
> I implement gc->get_direction() today, for the case to request one gpio as irq,
> gpio architecture will first call gpiochip_reqres_irq(), if the ROM or Uboot
> already config this gpio pin as OUTPUT mode, will get the following log:
> 
> [    2.714889] gpio gpiochip3: (43850000.gpio): gpiochip_lock_as_irq: tried to
> flag a GPIO set as output for IRQ
> [    2.724816] gpio gpiochip3: (43850000.gpio): unable to lock HW IRQ 11 for
> IRQ
> [    2.731972] genirq: Failed to request resources for 2-0050 (irq 211) on
> irqchip gpio-vf610
> 
> Any suggested method to avoid this case? My previous method works because
> driver lack of gc->get_direction().

Hi Linus,

I find gpio-hog can work around this case.

I add the following change, config this gpio as input in gpio-hog, so that when this gpio controller probe, gpiolib will setting the pin to input mode.

+&gpio5 {
+       ptn5110-int-hog {
+               gpio-hog;
+               gpios = <11 GPIO_ACTIVE_LOW>;
+               input;
        };

Not sure whether this is an acceptable method. If yes, what I need to do in the gpio-vf610 driver is to implement gc->get_direction() call back.

Best Regards
Haibo Chen
> 
> Best Regards
> Haibo Chen
> 
> >
> > Best Regards
> > Haibo Chen
> > >
> > > Yours,
> > > Linus Walleij