linux-kernel - Re: [PATCH] gpio/sifive: fix static checker warning

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Date:   Wed, 29 Jan 2020 10:27:49 +0900
From:   JaeJoon Jung <rgbi3307@...il.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Yash Shah <yash.shah@...ive.com>, atish.patra@....com,
        wesley@...ive.com, linus.walleij@...aro.org,
        linux-kernel@...r.kernel.org, bgolaszewski@...libre.com,
        Palmer Dabbelt <palmer@...belt.com>, sachin.ghadi@...ive.com,
        linux-gpio@...r.kernel.org,
        Paul Walmsley <paul.walmsley@...ive.com>,
        linux-riscv <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH] gpio/sifive: fix static checker warning

Because SiFive FU540 GPIO Registers are aligned 32-bit,
I think that irq_state is good "unsigned int" than "unsigned long".

I refer to SiFive FU540-C000 Manual v1p0 (GPIO Register Table 103)
as "Only naturally aligned 32-bit memory accesses are supported"

when you use assign_bit(offset, &chip->irq_state, 1),
offset is 32-bit.

I prefer to use bit operation instead of assign_bit().

u32 bit = BIT(offset);
chip->irq_state |= bit;

If you use this code, you do not use the assign_bit() and
need not change irq_state data type.

There are many improvements in my works for drivers/gpio/gpio-sifive.c.
I hope to check my attached source file.

On Tue, 28 Jan 2020 at 22:21, Marc Zyngier <maz@...nel.org> wrote:
>
> On 2020-01-28 05:24, Yash Shah wrote:
> > Typcasting "irq_state" leads to the below static checker warning:
> > The fix is to declare "irq_state" as unsigned long instead of u32.
> >
> >       drivers/gpio/gpio-sifive.c:97 sifive_gpio_irq_enable()
> >       warn: passing casted pointer '&chip->irq_state' to
> >       'assign_bit()' 32 vs 64.
> >
> > Fixes: 96868dce644d ("gpio/sifive: Add GPIO driver for SiFive SoCs")
> > Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
> > Signed-off-by: Yash Shah <yash.shah@...ive.com>
> > ---
> >  drivers/gpio/gpio-sifive.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpio/gpio-sifive.c b/drivers/gpio/gpio-sifive.c
> > index 147a1bd..c54dd08 100644
> > --- a/drivers/gpio/gpio-sifive.c
> > +++ b/drivers/gpio/gpio-sifive.c
> > @@ -35,7 +35,7 @@ struct sifive_gpio {
> >       void __iomem            *base;
> >       struct gpio_chip        gc;
> >       struct regmap           *regs;
> > -     u32                     irq_state;
> > +     unsigned long           irq_state;
> >       unsigned int            trigger[SIFIVE_GPIO_MAX];
> >       unsigned int            irq_parent[SIFIVE_GPIO_MAX];
> >  };
> > @@ -94,7 +94,7 @@ static void sifive_gpio_irq_enable(struct irq_data
> > *d)
> >       spin_unlock_irqrestore(&gc->bgpio_lock, flags);
> >
> >       /* Enable interrupts */
> > -     assign_bit(offset, (unsigned long *)&chip->irq_state, 1);
> > +     assign_bit(offset, &chip->irq_state, 1);
> >       sifive_gpio_set_ie(chip, offset);
> >  }
> >
> > @@ -104,7 +104,7 @@ static void sifive_gpio_irq_disable(struct irq_data
> > *d)
> >       struct sifive_gpio *chip = gpiochip_get_data(gc);
> >       int offset = irqd_to_hwirq(d) % SIFIVE_GPIO_MAX;
> >
> > -     assign_bit(offset, (unsigned long *)&chip->irq_state, 0);
> > +     assign_bit(offset, &chip->irq_state, 0);
> >       sifive_gpio_set_ie(chip, offset);
> >       irq_chip_disable_parent(d);
> >  }
>
> Yup, nice one. Should have spotted it.
>
> Reviewed-by: Marc Zyngier <maz@...nel.org>
>
> Linus, do you want me to queue this via the irqchip tree (given that
> it is where the original bug came from)? Or would you rather take it?
>
>          M.
> --
> Jazz is not dead. It just smells funny...
>

View attachment "gpio-sifive.c" of type "text/x-csrc" (13727 bytes)