[PATCH v6 08/16] ACPI: Add post_eject to struct acpi_scan_handler for cpu hotplug

Jonathan Cameron
2024-04-17T13:23:18Z

From: James Morse <james.morse@arm.com>

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: Joanthan Cameron <Jonathan.Cameron@huawei.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>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

----
v6:
- Switch to flags.
Russell, you hadn't signed off on this when posting last time.
Do you want to insert a suitable tag now?
v5:
- Rebase to take into account the changes to scan handling in the
meantime.
---
drivers/acpi/acpi_processor.c | 4 ++--
drivers/acpi/scan.c | 30 +++++++++++++++++++++++++++---
include/acpi/acpi_bus.h | 1 +
3 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
index 0cac77961020..0e43f5b4267a 100644
--- a/drivers/acpi/acpi_processor.c
+++ b/drivers/acpi/acpi_processor.c
@@ -481,7 +481,7 @@ 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;

@@ -650,7 +650,7 @@ 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,
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 1ec9677e6c2d..3ec54624664a 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -245,6 +245,7 @@ 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)
{
@@ -273,8 +274,6 @@ 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);
}
@@ -284,6 +283,28 @@ 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;
@@ -301,6 +322,7 @@ 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))
@@ -313,7 +335,7 @@ 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);
/*
@@ -336,6 +358,8 @@ 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;
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index e7796f373d0d..51a4b936f19e 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -129,6 +129,7 @@ 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;
--
2.39.2