ACPI / PM: Introduce efi poweroff for HW-full platforms without _S5

The problem is Linux registers pm_power_off = efi_power_off only if
we are in hardware reduced mode. Actually, what we also want is to do
this when ACPI S5 is simply not supported on non-legacy platforms.
Since some future Intel platforms are HW-full mode where the DSDT
fails to supply an _S5 object(without SLP_TYP), we should let such
kind of platform to leverage efi runtime service to poweroff.

This patch uses efi power off as first choice when S5 is unavailable,
even if there is a customized poweroff(driver provided, eg).
Meanwhile, the legacy platforms will not be affected because there is
no path for them to overwrite the pm_power_off to efi power off.

Suggested-by: Len Brown <len.brown@intel.com>
Reviewed-by: Matt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/drivers/acpi/sleep.c b/drivers/acpi/sleep.c
index 2a8b59644297..7a2e4d45b266 100644
--- a/drivers/acpi/sleep.c
+++ b/drivers/acpi/sleep.c
@@ -26,6 +26,11 @@
 #include "internal.h"
 #include "sleep.h"
 
+/*
+ * Some HW-full platforms do not have _S5, so they may need
+ * to leverage efi power off for a shutdown.
+ */
+bool acpi_no_s5;
 static u8 sleep_states[ACPI_S_STATE_COUNT];
 
 static void acpi_sleep_tts_switch(u32 acpi_state)
@@ -882,6 +887,8 @@ int __init acpi_sleep_init(void)
                 sleep_states[ACPI_STATE_S5] = 1;
                 pm_power_off_prepare = acpi_power_off_prepare;
                 pm_power_off = acpi_power_off;
+        } else {
+                acpi_no_s5 = true;
         }
 
         supported[0] = 0;