ACPI: Add post_eject to struct acpi_scan_handler for cpu hotplug

struct acpi_scan_handler has a detach callback that is used to remove
a driver when a bus is changed. When interacting with an eject-request,
the detach callback is called before _EJ0.

This means the ACPI processor driver can't use _STA to determine if a
CPU has been made not-present, or some of the other _STA bits have been
changed. acpi_processor_remove() needs to know the value of _STA after
_EJ0 has been called.

Add a post_eject callback to struct acpi_scan_handler. This is called
after acpi_scan_hot_remove() has successfully called _EJ0. Because
acpi_scan_check_and_detach() also clears the handler pointer,
it needs to be told if the caller will go on to call
acpi_bus_post_eject(), so that acpi_device_clear_enumerated()
and clearing the handler pointer can be deferred.
An extra flag is added to flags field introduced in the previous
patch to achieve this.
Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Tested-by: Miguel Luis <miguel.luis@oracle.com>
Tested-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
Tested-by: Jianyong Wu <jianyong.wu@arm.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20240529133446.28446-11-Jonathan.Cameron@huawei.comSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>

drivers/acpi/acpi_processor.c

@@ -475,7 +475,7 @@ static int acpi_processor_add(struct acpi_device *device,
 
 #ifdef CONFIG_ACPI_HOTPLUG_CPU
 /* Removal */
-static void acpi_processor_remove(struct acpi_device *device)
+static void acpi_processor_post_eject(struct acpi_device *device)
 {
 	struct acpi_processor *pr;
 
@@ -643,7 +643,7 @@ static struct acpi_scan_handler processor_handler = {
 	.ids = processor_device_ids,
 	.attach = acpi_processor_add,
 #ifdef CONFIG_ACPI_HOTPLUG_CPU
-	.detach = acpi_processor_remove,
+	.post_eject = acpi_processor_post_eject,
 #endif
 	.hotplug = {
 		.enabled = true,

drivers/acpi/scan.c

@@ -244,6 +244,7 @@ static int acpi_scan_try_to_offline(struct acpi_device *device)
 }
 
 #define ACPI_SCAN_CHECK_FLAG_STATUS	BIT(0)
+#define ACPI_SCAN_CHECK_FLAG_EJECT	BIT(1)
 
 static int acpi_scan_check_and_detach(struct acpi_device *adev, void *p)
 {
@@ -272,8 +273,6 @@ static int acpi_scan_check_and_detach(struct acpi_device *adev, void *p)
 	if (handler) {
 		if (handler->detach)
 			handler->detach(adev);
-
-		adev->handler = NULL;
 	} else {
 		device_release_driver(&adev->dev);
 	}
@@ -283,6 +282,28 @@ static int acpi_scan_check_and_detach(struct acpi_device *adev, void *p)
 	 */
 	acpi_device_set_power(adev, ACPI_STATE_D3_COLD);
 	adev->flags.initialized = false;
+
+	/* For eject this is deferred to acpi_bus_post_eject() */
+	if (!(flags & ACPI_SCAN_CHECK_FLAG_EJECT)) {
+		adev->handler = NULL;
+		acpi_device_clear_enumerated(adev);
+	}
+	return 0;
+}
+
+static int acpi_bus_post_eject(struct acpi_device *adev, void *not_used)
+{
+	struct acpi_scan_handler *handler = adev->handler;
+
+	acpi_dev_for_each_child_reverse(adev, acpi_bus_post_eject, NULL);
+
+	if (handler) {
+		if (handler->post_eject)
+			handler->post_eject(adev);
+
+		adev->handler = NULL;
+	}
+
 	acpi_device_clear_enumerated(adev);
 
 	return 0;
@@ -300,6 +321,7 @@ static int acpi_scan_hot_remove(struct acpi_device *device)
 	acpi_handle handle = device->handle;
 	unsigned long long sta;
 	acpi_status status;
+	uintptr_t flags = ACPI_SCAN_CHECK_FLAG_EJECT;
 
 	if (device->handler && device->handler->hotplug.demand_offline) {
 		if (!acpi_scan_is_offline(device, true))
@@ -312,7 +334,7 @@ static int acpi_scan_hot_remove(struct acpi_device *device)
 
 	acpi_handle_debug(handle, "Ejecting\n");
 
-	acpi_bus_trim(device);
+	acpi_scan_check_and_detach(device, (void *)flags);
 
 	acpi_evaluate_lck(handle, 0);
 	/*
@@ -335,6 +357,8 @@ static int acpi_scan_hot_remove(struct acpi_device *device)
 	} else if (sta & ACPI_STA_DEVICE_ENABLED) {
 		acpi_handle_warn(handle,
 			"Eject incomplete - status 0x%llx\n", sta);
+	} else {
+		acpi_bus_post_eject(device, NULL);
 	}
 
 	return 0;

include/acpi/acpi_bus.h

@@ -134,6 +134,7 @@ struct acpi_scan_handler {
 	bool (*match)(const char *idstr, const struct acpi_device_id **matchid);
 	int (*attach)(struct acpi_device *dev, const struct acpi_device_id *id);
 	void (*detach)(struct acpi_device *dev);
+	void (*post_eject)(struct acpi_device *dev);
 	void (*bind)(struct device *phys_dev);
 	void (*unbind)(struct device *phys_dev);
 	struct acpi_hotplug_profile hotplug;