From 81fe79da00f4130ef329d22d6b9433f1ff7f2b6f Mon Sep 17 00:00:00 2001 From: Phil Elwell <phil@raspberrypi.com> Date: Mon, 26 Apr 2021 09:58:14 +0100 Subject: [PATCH] overlays: README - improve the gpio-poweroff guide Signed-off-by: Phil Elwell <phil@raspberrypi.com> --- arch/arm/boot/dts/overlays/README | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) --- a/arch/arm/boot/dts/overlays/README +++ b/arch/arm/boot/dts/overlays/README @@ -987,8 +987,15 @@ Params: <None> Name: gpio-poweroff -Info: Drives a GPIO high or low on poweroff (including halt). Enabling this - overlay will prevent the ability to boot by driving GPIO3 low. +Info: Drives a GPIO high or low on poweroff (including halt). Using this + overlay interferes with the normal power-down sequence, preventing the + kernel from resetting the SoC (a necessary step in a normal power-off + or reboot). This also disables the ability to triger a boot by driving + GPIO3 low. + + Users of this overlay are required to provide an external mechanism to + switch off the power supply when signalled - failure to do so results + in a kernel BUG, increased power consumption and undefined behaviour. Load: dtoverlay=gpio-poweroff,<param>=<val> Params: gpiopin GPIO for signalling (default 26)