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

[Michael Trimarchi]

On 06/21/2013 06:40 AM, Vipin Kumar wrote:
> 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
> 

The problem is not in set one bit but in reset one bit. Can you check
the else path?


Michael


> Regards
> Vipin
> 
>> Thanks,
>> Axel
>> .
>>
> 
> _______________________________________________
> U-Boot mailing list
> U-Boot at lists.denx.de
> http://lists.denx.de/mailman/listinfo/u-boot