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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)
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