Re: [U-Boot] [PATCH] gpio: spear_gpio: Fix gpio_set_value() implementation

[Axel Lin]

2013/6/20 Marek Vasut <ma...@denx.de>
>
> Dear Axel Lin,
>
> > In current gpio_set_value() implementation, it always sets the gpio control
> > bit no matter the value argument is 0 or 1. Thus the GPIOs never set to
> > low. This patch fixes this bug.
> >
> > Signed-off-by: Axel Lin <axel....@ingics.com>
> > ---
> >  drivers/gpio/spear_gpio.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpio/spear_gpio.c b/drivers/gpio/spear_gpio.c
> > index d3c728e..8878608 100644
> > --- a/drivers/gpio/spear_gpio.c
> > +++ b/drivers/gpio/spear_gpio.c
> > @@ -52,7 +52,10 @@ int gpio_set_value(unsigned gpio, int value)
> >  {
> >       struct gpio_regs *regs = (struct gpio_regs *)CONFIG_GPIO_BASE;
> >
> > -     writel(1 << gpio, &regs->gpiodata[DATA_REG_ADDR(gpio)]);
> > +     if (value)
> > +             writel(1 << gpio, &regs->gpiodata[DATA_REG_ADDR(gpio)]);
> > +     else
> > +             writel(0, &regs->gpiodata[DATA_REG_ADDR(gpio)]);
>
> How can this possibly work? Writing 0 to the whole bank will unset all the
> GPIOs, no ?


Because each GPIO is controlled by a register.
And only one bit will be set when set gpio to high.

So it's safe to write 0 for clearing the bit.

Note, the gpio_get_value() implementation also assumes there is only one bit
will be set. ( If this is not true, both gpio_get_value() and gpio_set_value()
need fix.)

Vipin, can you review this patch and confirm this behavior?

Thanks,
Axel
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