From: David Woodhouse <dwmw@amazon.co.uk>
Date: Mon, 11 Mar 2024 13:29:02 +0000 (+0000)
Subject: arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=refs%2Fheads%2Fpsci-hibernate-5.15;p=users%2Fdwmw2%2Flinux.git

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 cfb448eabdaa2..8aaa8dc4a08b4 100644
--- 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 9abc73d500fbf..d584e53c72141 100644
--- 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();