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

[Vipin Kumar]

On 6/20/2013 7:26 PM, Axel Lin wrote:
> 2013/6/20 Marek Vasut<marex at 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.lin at 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?
>

Yes this is right. and the code is fine

Regards
Vipin

> Thanks,
> Axel
> .
>