4.14-stable review patch. If anyone has any objections, please let me know.
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From: Josua Mayer josua@solid-run.com
commit b2f750c3a80b285cd60c9346f8c96bd0a2a66cde upstream.
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 josua@solid-run.com Link: https://lore.kernel.org/r/20231004163928.14609-1-josua@solid-run.com Signed-off-by: Johannes Berg johannes.berg@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/rfkill/rfkill-gpio.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/net/rfkill/rfkill-gpio.c +++ b/net/rfkill/rfkill-gpio.c @@ -111,13 +111,13 @@ static int rfkill_gpio_probe(struct plat
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);