arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate

The PSCI v1.3 specification (alpha) adds support for a SYSTEM_OFF2
function which is analogous to ACPI S4 state. This will allow hosting
environments to determine that a guest is hibernated rather than just
powered off, and handle that state appropriately on subsequent launches.

Since commit 60c0d45a7f7a ("efi/arm64: use UEFI for system reset and
poweroff") the EFI shutdown method is deliberately preferred over PSCI
or other methods. So register a SYS_OFF_MODE_POWER_OFF handler which
*only* handles the hibernation, leaving the original PSCI SYSTEM_OFF as
a last resort via the legacy pm_power_off function pointer.

The hibernation code already exports a system_entering_hibernation()
function which is be used by the higher-priority handler to check for
hibernation. That existing function just returns the value of a static
boolean variable from hibernate.c, which was previously only set in the
hibernation_platform_enter() code path. Set the same flag in the simpler
code path around the call to kernel_power_off() too.

An alternative way to hook SYSTEM_OFF2 into the hibernation code would
be to register a platform_hibernation_ops structure with an ->enter()
method which makes the new SYSTEM_OFF2 call. But that would have the
unwanted side-effect of making hibernation take a completely different
code path in hibernation_platform_enter(), invoking a lot of special dpm
callbacks.

Another option might be to add a new SYS_OFF_MODE_HIBERNATE mode, with
fallback to SYS_OFF_MODE_POWER_OFF. Or to use the sys_off_data to
indicate whether the power off is for hibernation.

But this version works and is relatively simple.

[5.15: Override pm_power_off() like EFI does (and *after* EFI does).]
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>

diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
index cfb448eabdaa22e367c5f9159cdc9ddfd782332f..8aaa8dc4a08b4b1dd90f7f16ef1c0c1c51c3e900 100644 (file)
--- a/drivers/firmware/psci/psci.c
+++ b/drivers/firmware/psci/psci.c
@@ -77,6 +77,7 @@ struct psci_0_1_function_ids get_psci_0_1_function_ids(void)
 
 static u32 psci_cpu_suspend_feature;
 static bool psci_system_reset2_supported;
+static bool psci_system_off2_hibernate_supported;
 
 static inline bool psci_has_ext_power_state(void)
 {
@@ -324,6 +325,31 @@ static void psci_sys_poweroff(void)
        invoke_psci_fn(PSCI_0_2_FN_SYSTEM_OFF, 0, 0, 0);
 }
 
+#ifdef CONFIG_HIBERNATION
+static void (*psci_orig_pm_power_off)(void);
+
+static void psci_sys_hibernate(void)
+{
+       if (system_entering_hibernation())
+               invoke_psci_fn(PSCI_FN_NATIVE(1_3, SYSTEM_OFF2),
+                              PSCI_1_3_HIBERNATE_TYPE_OFF, 0, 0);
+       if (psci_orig_pm_power_off)
+              psci_orig_pm_power_off();
+       psci_sys_poweroff();
+}
+
+static int __init psci_hibernate_init(void)
+{
+       /* This runs *later* than efi_shutdown_init */
+       if (psci_system_off2_hibernate_supported) {
+               psci_orig_pm_power_off = pm_power_off;
+               pm_power_off = psci_sys_hibernate;
+       }
+       return 0;
+}
+late_initcall(psci_hibernate_init);
+#endif
+
 static int __init psci_features(u32 psci_func_id)
 {
        return invoke_psci_fn(PSCI_1_0_FN_PSCI_FEATURES,
@@ -385,6 +411,18 @@ static void __init psci_init_system_reset2(void)
                psci_system_reset2_supported = true;
 }
 
+static void __init psci_init_system_off2(void)
+{
+       int ret;
+
+       ret = psci_features(PSCI_FN_NATIVE(1_3, SYSTEM_OFF2));
+       if (ret < 0)
+               return;
+
+       if (ret & BIT(PSCI_1_3_HIBERNATE_TYPE_OFF))
+               psci_system_off2_hibernate_supported = true;
+}
+
 static void __init psci_init_system_suspend(void)
 {
        int ret;
@@ -515,6 +553,7 @@ static int __init psci_probe(void)
                psci_init_cpu_suspend();
                psci_init_system_suspend();
                psci_init_system_reset2();
+               psci_init_system_off2();
                kvm_init_hyp_services();
        }
 

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 9abc73d500fbfe1988d703c4b4dccd7deaf0381f..d584e53c7214110d83b36a9f5fd28f79731230d8 100644 (file)
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -664,8 +664,11 @@ static void power_down(void)
                hibernation_platform_enter();
                fallthrough;
        case HIBERNATION_SHUTDOWN:
-               if (pm_power_off)
+               if (pm_power_off) {
+                       entering_platform_hibernation = true;
                        kernel_power_off();
+                       entering_platform_hibernation = false;
+               }
                break;
        }
        kernel_halt();