GPIO 96 AM335x

Hi Leonardo,

Which AM335x board are you using? The GP EVM, the Starter Kit or the BeagleBone?

Best regards,
Miroslav

GP EVM.

Leonardo

Hi Leonardo,

Please take a look at the gpiolib.c file: http://lxr.free-electrons.com/source/drivers/gpio/gpiolib.c
The [auto] label means that the GPIO pin has been autorequested. I quote:

/* Warn when drivers omit gpio_request() calls -- legal but ill-advised
 * when setting direction, and otherwise illegal.  Until board setup code
 * and drivers use explicit requests everywhere (which won't happen when
 * those calls have no teeth) we can't avoid autorequesting.  This nag
 * message should motivate switching to explicit requests... so should
 * the weaker cleanup after faults, compared to gpio_request().
 *
 * NOTE: the autorequest mechanism is going away; at this point it's
 * only "legal" in the sense that (old) code using it won't break yet,
 * but instead only triggers a WARN() stack dump.
 */
static int gpio_ensure_requested(struct gpio_desc *desc, unsigned offset)
{
    const struct gpio_chip *chip = desc->chip;
    const int gpio = chip->base + offset;

    /* Debug prints */
    if (gpio == 96) {
        printk(KERN_ALERT "**********\n");
        dump_stack();
        printk(KERN_ALERT "**********\n");
    }

    if (WARN(test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0,
            "autorequest GPIO-%d\n", gpio)) {
        if (!try_module_get(chip->owner)) {
            pr_err("GPIO-%d: module can't be gotten \n", gpio);
            clear_bit(FLAG_REQUESTED, &desc->flags);
            /* lose */
            return -EIO;
        }
        desc_set_label(desc, "[auto]");
        /* caller must chip->request() w/o spinlock */
        if (chip->request)
            return 1;
    }
    return 0;
}

You can try and dump the stack inside the gpio_ensure_requested() function. Something like this:

if (gpio == 96) {
        printk(KERN_ALERT "**********\n");
        dump_stack();
        printk(KERN_ALERT "**********\n");
}

Then recompile the kernel. This will dump the call stack and you can check which module is using GPIO #96.

Best regards,
Miroslav