From b2f750c3a80b285cd60c9346f8c96bd0a2a66cde Mon Sep 17 00:00:00 2001 From: Josua Mayer Date: Wed, 4 Oct 2023 18:39:28 +0200 Subject: [PATCH] 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. Fixes: 7176ba23f8b5 ("net: rfkill: add generic gpio rfkill driver") Signed-off-by: Josua Mayer Link: https://lore.kernel.org/r/20231004163928.14609-1-josua@solid-run.com Signed-off-by: Johannes Berg --- net/rfkill/rfkill-gpio.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/rfkill/rfkill-gpio.c b/net/rfkill/rfkill-gpio.c index e9d1b2f..5a81505 100644 --- a/net/rfkill/rfkill-gpio.c +++ b/net/rfkill/rfkill-gpio.c @@ -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); -- 2.7.4