gpio: sysfs: fix redundant lock-as-irq handling

Drivers should call gpiochip_lock_as_irq (which prevents the pin
direction from being changed) in their irq_request_resources callbacks
but some drivers currently fail to do so.

Instead a second, explicit and often redundant call to lock-as-irq is
made by the sysfs-interface implementation after an irq has been
requested.

Move the explicit call before the irq-request to match the unlock done
after the irq is later released. Note that this also fixes an irq leak,
should the explicit call ever have failed.

Also add a comment about removing the redundant call once the broken
drivers have been fixed.

Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpiolib-sysfs.c

@@ -195,20 +195,28 @@ static int gpio_setup_irq(struct gpio_desc *desc, struct device *dev,
 		}
 	}
 
-	ret = request_any_context_irq(irq, gpio_sysfs_irq, irq_flags,
-				"gpiolib", value_sd);
+	/*
+	 * FIXME: This should be done in the irq_request_resources callback
+	 *        when the irq is requested, but a few drivers currently fail
+	 *        to do so.
+	 *
+	 *        Remove this redundant call (along with the corresponding
+	 *        unlock) when those drivers have been fixed.
+	 */
+	ret = gpiochip_lock_as_irq(desc->chip, gpio_chip_hwgpio(desc));
 	if (ret < 0)
 		goto free_id;
 
-	ret = gpiochip_lock_as_irq(desc->chip, gpio_chip_hwgpio(desc));
-	if (ret < 0) {
-		gpiod_warn(desc, "failed to flag the GPIO for IRQ\n");
-		goto free_id;
-	}
+	ret = request_any_context_irq(irq, gpio_sysfs_irq, irq_flags,
+				"gpiolib", value_sd);
+	if (ret < 0)
+		goto err_unlock;
 
 	desc->flags |= gpio_flags;
 	return 0;
 
+err_unlock:
+	gpiochip_unlock_as_irq(desc->chip, gpio_chip_hwgpio(desc));
 free_id:
 	idr_remove(&dirent_idr, id);
 	desc->flags &= GPIO_FLAGS_MASK;