net: rfkill: gpio: prevent value glitch during probe

When either reset- or shutdown-gpio have are initially deasserted, e.g. after a reboot - or when the hardware does not include pull-down, there will be a short toggle of both IOs to logical 0 and back to 1.

It seems that the rfkill default is unblocked, so the driver should not glitch to output low during probe.
It can lead e.g. to unexpected lte modem reconnect:

[1] root@localhost:~# dmesg | grep "usb 2-1"

[    2.136124] usb 2-1: new SuperSpeed USB device number 2 using xhci-hcd
[   21.215278] usb 2-1: USB disconnect, device number 2
[   28.833977] usb 2-1: new SuperSpeed USB device number 3 using xhci-hcd

The glitch has been discovered on an arm64 board, now that device-tree support for the rfkill-gpio driver has finally appeared :).

Change the flags for devm_gpiod_get_optional from GPIOD_OUT_LOW to GPIOD_ASIS to avoid any glitches.
The rfkill driver will set the intended value during rfkill_sync_work.

---
 net/rfkill/rfkill-gpio.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

index e9d1b2f2ff0a..5a81505fba9a 100644
@@ -108,13 +108,13 @@ static int rfkill_gpio_probe(struct platform_device *pdev)
 
 	rfkill->clk = devm_clk_get(&pdev->dev, NULL);
 
-	gpio = devm_gpiod_get_optional(&pdev->dev, "reset", GPIOD_OUT_LOW);
+	gpio = devm_gpiod_get_optional(&pdev->dev, "reset", GPIOD_ASIS);
 	if (IS_ERR(gpio))
 		return PTR_ERR(gpio);
 
 	rfkill->reset_gpio = gpio;
 
-	gpio = devm_gpiod_get_optional(&pdev->dev, "shutdown", GPIOD_OUT_LOW);
+	gpio = devm_gpiod_get_optional(&pdev->dev, "shutdown", GPIOD_ASIS);
 	if (IS_ERR(gpio))
 		return PTR_ERR(gpio);
 

2.35.3