linux-kernel - Re: problems with GPIO

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Date:	Wed, 2 Mar 2011 23:24:14 -0700
From:	Grant Likely <grant.likely@...retlab.ca>
To:	"Murali K. Vemuri" <vemuri.muralikrishna@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: problems with GPIO

On Thu, Feb 17, 2011 at 9:21 PM, Murali K. Vemuri
<vemuri.muralikrishna@...il.com> wrote:
> Hi There,
>
> I am rather a novice with linux kernel and I have this problem.
> My board is  OMAP 3530 based and I use GPIO 21 to detect an external
> device plug-in.
> Now, when the board is just booted (after a complete power disconnect
> ), the GPIO is high, and when I plug in my external device, the GPIO
> goes low, and I am able to detect it.
> However, I see the voltage level still low after I remove the external
> plug-in, and any further plug-ins, remain un-detected.
> My H/W engineers say it is some config I am missing in Kernel.
> can someone point me?
>
> my code snippet is like:
>
>    omap_mux_init_gpio(MY_GPIO,  OMAP_PIN_INPUT_PULLDOWN  );
>    gpio_request(MY_GPIO,"CABLE IN");
>    gpio_direction_input(MY_GPIO);
>    gpio_set_value(MY_GPIO,1);

It depends on the gpio controller driver, but gpio_set_value() is very
likely switching the GPIO pin from input to output.  Why are you
calling gpio_set_value()?

g.
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