suspend: early CPU offlining for T2 Macs (#52)

Add the standalone ACPI patch using Apple T2 PCI bridge detection so the fix does not depend on the experimental shared T2 platform identification series.
2026-08-16 05:18:17 -07:00 · 2026-07-30 10:22:07 +05:30
parent d26b6dfd00
commit 45b600a438
1 changed files with 174 additions and 0 deletions
@@ -0,0 +1,174 @@
+From ccb4c5eb64213b5fd0876b27dac86b2f1bbd6e2b Mon Sep 17 00:00:00 2001
+From: Andre Eikmeyer <dev@deq.rocks>
+Date: Fri, 24 Jul 2026 17:37:27 +0200
+Subject: [PATCH] ACPI: x86: Apple T2 systems need early CPU offlining
+
+Linux reports _OSI("Darwin") on x86 Apple systems. On T2 Macs, the
+selected firmware suspend path makes secondary CPU startup during early
+resume take several seconds per CPU. The same CPUs can be brought online
+normally after platform resume.
+
+We therefore move secondary CPU hotplug outside the generic CPU PM
+notifier window on systems exposing the Apple T2 PCI bridge. A prepare
+notifier runs before the CPU core blocks hotplug, while a post notifier
+restores only the CPUs it removed after the core enables hotplug again.
+
+This reduces CPU bring-up during resume from several seconds per CPU to a
+fraction of a second. The change was tested on MacBookPro15,1,
+MacBookPro16,2, MacBookAir9,1 and a 27-inch T2 iMac.
+
+Signed-off-by: Andre Eikmeyer <dev@deq.rocks>
+---
+ drivers/acpi/x86/apple.c | 131 +++++++++++++++++++++++++++++++++++++++
+ 1 file changed, 131 insertions(+)
+
+diff --git a/drivers/acpi/x86/apple.c b/drivers/acpi/x86/apple.c
+index 45d0f16f374f..2522593163f5 100644
+--- a/drivers/acpi/x86/apple.c
+++ b/drivers/acpi/x86/apple.c
+@@ -6,7 +6,13 @@
+ 
+ #include <linux/acpi.h>
+ #include <linux/bitmap.h>
+#include <linux/cpu.h>
+#include <linux/cpuhplock.h>
+#include <linux/init.h>
+#include <linux/notifier.h>
+#include <linux/pci.h>
+ #include <linux/platform_data/x86/apple.h>
+#include <linux/suspend.h>
+ #include <linux/uuid.h>
+ #include "../internal.h"
+ 
+@@ -146,3 +152,128 @@ void acpi_extract_apple_properties(struct acpi_device *adev)
+ 	ACPI_FREE(props);
+ 	bitmap_free(valid);
+ }
+
+#ifdef CONFIG_PM_SLEEP_SMP
+#define PCI_DEVICE_ID_APPLE_T2_BRIDGE 0x1801
+
+/*
+ * The ACPI path selected by _OSI("Darwin") leaves Apple T2 systems in a
+ * state where bringing secondary CPUs online during early resume may take
+ * several seconds per CPU. Normal CPU hotplug after platform resume is not
+ * affected, so move it outside the generic suspend CPU hotplug window.
+ */
+static cpumask_var_t apple_t2_offlined_cpus;
+
+static void apple_t2_restore_cpus(void)
+{
+	unsigned int cpu;
+	int ret;
+
+	for_each_cpu(cpu, apple_t2_offlined_cpus) {
+		ret = add_cpu(cpu);
+		if (ret) {
+			pr_err("ACPI: Apple T2 failed to restore CPU%u: %d\n",
+			       cpu, ret);
+			continue;
+		}
+
+		cpumask_clear_cpu(cpu, apple_t2_offlined_cpus);
+	}
+}
+
+static void apple_t2_offline_cpus(void)
+{
+	unsigned int cpu;
+	int ret;
+
+	if (!cpumask_empty(apple_t2_offlined_cpus)) {
+		pr_err("ACPI: Apple T2 CPUs from the previous suspend remain offline\n");
+		apple_t2_restore_cpus();
+		if (!cpumask_empty(apple_t2_offlined_cpus)) {
+			pr_err("ACPI: Apple T2 early CPU offlining skipped\n");
+			return;
+		}
+	}
+
+	for_each_online_cpu(cpu) {
+		if (cpu == 0)
+			continue;
+
+		ret = remove_cpu(cpu);
+		if (ret) {
+			pr_err("ACPI: Apple T2 failed to offline CPU%u: %d\n",
+			       cpu, ret);
+			continue;
+		}
+
+		cpumask_set_cpu(cpu, apple_t2_offlined_cpus);
+	}
+}
+
+static int apple_t2_cpu_prepare(struct notifier_block *nb,
+				unsigned long action, void *unused)
+{
+	if (action == PM_SUSPEND_PREPARE)
+		apple_t2_offline_cpus();
+
+	return NOTIFY_OK;
+}
+
+static int apple_t2_cpu_restore(struct notifier_block *nb,
+				unsigned long action, void *unused)
+{
+	if (action == PM_POST_SUSPEND)
+		apple_t2_restore_cpus();
+
+	return NOTIFY_OK;
+}
+
+/*
+ * The CPU core PM notifier runs at priority 0. Offline CPUs before it blocks
+ * hotplug, then restore them after it enables hotplug again.
+ */
+static struct notifier_block apple_t2_cpu_prepare_nb = {
+	.notifier_call = apple_t2_cpu_prepare,
+	.priority = 1,
+};
+
+static struct notifier_block apple_t2_cpu_restore_nb = {
+	.notifier_call = apple_t2_cpu_restore,
+	.priority = -1,
+};
+
+static int __init apple_t2_cpu_pm_init(void)
+{
+	struct pci_dev *t2;
+	int ret;
+
+	if (!x86_apple_machine)
+		return 0;
+
+	t2 = pci_get_device(PCI_VENDOR_ID_APPLE,
+			    PCI_DEVICE_ID_APPLE_T2_BRIDGE, NULL);
+	if (!t2)
+		return 0;
+	pci_dev_put(t2);
+
+	if (!alloc_cpumask_var(&apple_t2_offlined_cpus, GFP_KERNEL))
+		return -ENOMEM;
+
+	ret = register_pm_notifier(&apple_t2_cpu_prepare_nb);
+	if (ret)
+		goto free_mask;
+
+	ret = register_pm_notifier(&apple_t2_cpu_restore_nb);
+	if (ret)
+		goto unregister_prepare;
+
+	return 0;
+
+unregister_prepare:
+	unregister_pm_notifier(&apple_t2_cpu_prepare_nb);
+free_mask:
+	free_cpumask_var(apple_t2_offlined_cpus);
+	return ret;
+}
+late_initcall(apple_t2_cpu_pm_init);
+#endif
+-- 
+2.55.0
+