Re: [patch 2.6.20-rc1 5/6] SA1100 GPIO wrappers

Nicolas Pitre
2006-12-30T03:15:33Z

On Fri, 29 Dec 2006, David Brownell wrote:

> Here's a version that compiles ...

This patch is completely broken.

> Arch-neutral GPIO calls for PXA.

This is not PXA but SA1100 to start with.

> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
>
> Index: pxa/include/asm-arm/arch-sa1100/gpio.h
> ===================================================================
> --- /dev/null 1970-01-01 00:00:00.000000000 +0000
> +++ pxa/include/asm-arm/arch-sa1100/gpio.h 2006-12-29
> 18:21:00.000000000 -0800
> @@ -0,0 +1,100 @@

[...]

> +static inline int gpio_direction_input(unsigned gpio)
> +{
> + if (gpio > GPIO_MAX)
> + return -EINVAL;
> + GPDR = (GPDR_In << gpio);

This is crap. It will expand to GPDR = 0 effectively making _all_ gpios
as input.

What you want here is:

GPDR &= ~(1 << gpio);

and you most probably need to protect the implied read-modify-write
cycle with a spinlock unless the generic gpio API expects this
protection is the responsibility of the caller.

> +static inline int gpio_direction_output(unsigned gpio)
> +{
> + if (gpio > GPIO_MAX)
> + return -EINVAL;
> + GPDR = (GPDR_Out << gpio);

Same issue, although this would make all gpios as input except for the
specified one.

What you want is:

GPDR |= (1 << gpio);

And again spinlock protection is probably needed.

> +static inline int __gpio_get_value(unsigned gpio)
> +{
> + return GPLR & GPIO_GPIO(gpio);
> +}
> +
> +#define gpio_get_value(gpio) \
> + (__builtin_constant_p(gpio) \
> + ? __gpio_get_value(gpio) \
> + : sa1100_gpio_get_value(gpio))
> +

Please drop the out of line version. It will always be more costly than
the inline version even for non constant gpio values. And I think the
usage of GPIO_GPIO(gpio) is more obfuscating than directly using
(1 << gpio).

> +static inline void __gpio_set_value(unsigned gpio, int value)
> +{
> + if (value)
> + GPSR = GPIO_GPIO(gpio);
> + else
> + GPCR = GPIO_GPIO(gpio);
> +}
> +
> +#define gpio_set_value(gpio,value) \
> + (__builtin_constant_p(gpio) \
> + ? __gpio_set_value(gpio, value) \
> + : sa1100_gpio_set_value(gpio, value))

Same as above.

Nicolas