Re: [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<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?

Yes this is right. and the code is fine

Regards
Vipin

Thanks,
Axel
.

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