platform/x86: x86-android-tablets: Fix Lenovo Yoga Tablet 2 830/1050 poweroff again

Commit 98f30d0e ("ACPI: power: Switch to sys-off handler API")
switched the ACPI sleep code from directly setting the old global
pm_power_off handler to using the new register_sys_off_handler()
mechanism with a priority of SYS_OFF_PRIO_FIRMWARE.

This is a problem in special cases where the old global pm_power_off
handler later gets overwritten, such as the Lenovo Tab2 poweroff bugfix
in x86-android-tablets. The old global pm_power_off handler gets run
with a priority of SYS_OFF_PRIO_DEFAULT which is lower then
SYS_OFF_PRIO_FIRMWARE, causing the troublesome ACPI poweroff (which
freezes the system) to run first.

Switch the registering of lenovo_yoga_tab2_830_1050_power_off over to
register_sys_off_handler() with a priority of SYS_OFF_PRIO_FIRMWARE + 1
so that it will run before acpi_power_off() to fix this.

Fixes: 98f30d0e ("ACPI: power: Switch to sys-off handler API")
Cc: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20220708131412.81078-2-hdegoede@redhat.com

drivers/platform/x86/x86-android-tablets.c

@@ -27,8 +27,8 @@
 #include <linux/pinctrl/machine.h>
 #include <linux/platform_data/lp855x.h>
 #include <linux/platform_device.h>
-#include <linux/pm.h>
 #include <linux/power/bq24190_charger.h>
+#include <linux/reboot.h>
 #include <linux/rmi.h>
 #include <linux/serdev.h>
 #include <linux/spi/spi.h>
@@ -889,6 +889,7 @@ static const struct pinctrl_map lenovo_yoga_tab2_830_1050_codec_pinctrl_map =
 			  "INT33FC:02", "pmu_clk2_grp", "pmu_clk");
 
 static struct pinctrl *lenovo_yoga_tab2_830_1050_codec_pinctrl;
+static struct sys_off_handler *lenovo_yoga_tab2_830_1050_sys_off_handler;
 
 static int __init lenovo_yoga_tab2_830_1050_init_codec(void)
 {
@@ -933,9 +934,11 @@ static int __init lenovo_yoga_tab2_830_1050_init_codec(void)
  * followed by a normal 3 second press to recover. Avoid this by doing an EFI
  * poweroff instead.
  */
-static void lenovo_yoga_tab2_830_1050_power_off(void)
+static int lenovo_yoga_tab2_830_1050_power_off(struct sys_off_data *data)
 {
 	efi.reset_system(EFI_RESET_SHUTDOWN, EFI_SUCCESS, 0, NULL);
+
+	return NOTIFY_DONE;
 }
 
 static int __init lenovo_yoga_tab2_830_1050_init(void)
@@ -950,13 +953,19 @@ static int __init lenovo_yoga_tab2_830_1050_init(void)
 	if (ret)
 		return ret;
 
-	pm_power_off = lenovo_yoga_tab2_830_1050_power_off;
+	/* SYS_OFF_PRIO_FIRMWARE + 1 so that it runs before acpi_power_off */
+	lenovo_yoga_tab2_830_1050_sys_off_handler =
+		register_sys_off_handler(SYS_OFF_MODE_POWER_OFF, SYS_OFF_PRIO_FIRMWARE + 1,
+					 lenovo_yoga_tab2_830_1050_power_off, NULL);
+	if (IS_ERR(lenovo_yoga_tab2_830_1050_sys_off_handler))
+		return PTR_ERR(lenovo_yoga_tab2_830_1050_sys_off_handler);
+
 	return 0;
 }
 
 static void lenovo_yoga_tab2_830_1050_exit(void)
 {
-	pm_power_off = NULL; /* Just turn poweroff into halt on module unload */
+	unregister_sys_off_handler(lenovo_yoga_tab2_830_1050_sys_off_handler);
 
 	if (lenovo_yoga_tab2_830_1050_codec_pinctrl) {
 		pinctrl_put(lenovo_yoga_tab2_830_1050_codec_pinctrl);