gpio-poweroff: Allow it to work on Raspberry Pi

The Raspberry Pi firmware manages the power-down and reboot
process. To do this it installs a pm_power_off handler, causing
the gpio-poweroff module to abort the probe function.

This patch introduces a "force" DT property that overrides that
behaviour, and also adds a DT overlay to enable and control it.

Note that running in an active-low configuration (DT parameter
"active_low") requires a custom dt-blob.bin and probably won't
allow a reboot without switching off, so an external inversion
of the trigger signal may be preferable.

diff --git a/drivers/power/reset/gpio-poweroff.c b/drivers/power/reset/gpio-poweroff.c
index b28f24d..e41e64a 100644 (file)
--- a/drivers/power/reset/gpio-poweroff.c
+++ b/drivers/power/reset/gpio-poweroff.c
@@ -11,6 +11,7 @@
 #include <linux/init.h>
 #include <linux/delay.h>
 #include <linux/platform_device.h>
+#include <linux/of.h>
 #include <linux/property.h>
 #include <linux/gpio/consumer.h>
 #include <linux/mod_devicetable.h>
@@ -51,9 +52,11 @@ static int gpio_poweroff_probe(struct platform_device *pdev)
 {
        bool input = false;
        enum gpiod_flags flags;
+       bool force = false;
 
        /* If a pm_power_off function has already been added, leave it alone */
-       if (pm_power_off != NULL) {
+       force = of_property_read_bool(pdev->dev.of_node, "force");
+       if (!force && (pm_power_off != NULL)) {
                dev_err(&pdev->dev,
                        "%s: pm_power_off function already registered\n",
                       __func__);