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Subject[PATCH v2 4/8] firmware: arm_scmi: make notifications aware of protocol usage
Date
Account any active notifications registered notifier against the proper
related protocol; do not consider pending venet handlers, only active event
handlers will concur to protocol usage accounting.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
---
drivers/firmware/arm_scmi/notify.c | 50 +++++++++++++++++++++++++-----
1 file changed, 43 insertions(+), 7 deletions(-)

diff --git a/drivers/firmware/arm_scmi/notify.c b/drivers/firmware/arm_scmi/notify.c
index 64d43e425644..1ac73f51374b 100644
--- a/drivers/firmware/arm_scmi/notify.c
+++ b/drivers/firmware/arm_scmi/notify.c
@@ -367,7 +367,7 @@ static struct scmi_event_handler *
scmi_get_active_handler(struct scmi_notify_instance *ni, u32 evt_key);
static void scmi_put_active_handler(struct scmi_notify_instance *ni,
struct scmi_event_handler *hndl);
-static void scmi_put_handler_unlocked(struct scmi_notify_instance *ni,
+static bool scmi_put_handler_unlocked(struct scmi_notify_instance *ni,
struct scmi_event_handler *hndl);

/**
@@ -899,9 +899,21 @@ static inline int scmi_bind_event_handler(struct scmi_notify_instance *ni,
if (!r_evt)
return -EINVAL;

- /* Remove from pending and insert into registered */
+ /*
+ * Remove from pending and insert into registered while getting hold
+ * of protocol instance.
+ */
hash_del(&hndl->hash);
+ /*
+ * Acquire protocols only for NON pending handlers, so as NOT to trigger
+ * protocol initialization when a notifier is registered against a still
+ * not registered protocol, since it would make little sense to force init
+ * protocols for which still no SCMI driver user exists: they wouldn't
+ * emit any event anyway till some SCMI driver starts using it.
+ */
+ scmi_acquire_protocol(ni->handle, KEY_XTRACT_PROTO_ID(hndl->key));
hndl->r_evt = r_evt;
+
mutex_lock(&r_evt->proto->registered_mtx);
hash_add(r_evt->proto->registered_events_handlers,
&hndl->hash, hndl->key);
@@ -1192,41 +1204,65 @@ static int scmi_disable_events(struct scmi_event_handler *hndl)
* * unregister and free the handler itself
*
* Context: Assumes all the proper locking has been managed by the caller.
+ *
+ * Return: True if handler was freed (users dropped to zero)
*/
-static void scmi_put_handler_unlocked(struct scmi_notify_instance *ni,
+static bool scmi_put_handler_unlocked(struct scmi_notify_instance *ni,
struct scmi_event_handler *hndl)
{
+ bool freed = false;
+
if (refcount_dec_and_test(&hndl->users)) {
if (!IS_HNDL_PENDING(hndl))
scmi_disable_events(hndl);
scmi_free_event_handler(hndl);
+ freed = true;
}
+
+ return freed;
}

static void scmi_put_handler(struct scmi_notify_instance *ni,
struct scmi_event_handler *hndl)
{
+ bool freed;
+ u8 protocol_id;
struct scmi_registered_event *r_evt = hndl->r_evt;

mutex_lock(&ni->pending_mtx);
- if (r_evt)
+ if (r_evt) {
+ protocol_id = r_evt->proto->id;
mutex_lock(&r_evt->proto->registered_mtx);
+ }

- scmi_put_handler_unlocked(ni, hndl);
+ freed = scmi_put_handler_unlocked(ni, hndl);

- if (r_evt)
+ if (r_evt) {
mutex_unlock(&r_evt->proto->registered_mtx);
+ /*
+ * Only registered handler acquired protocol; must be here
+ * released only AFTER unlocking registered_mtx, since
+ * releasing a protocol can trigger its de-initialization
+ * (ie. including r_evt and registered_mtx)
+ */
+ if (freed)
+ scmi_release_protocol(ni->handle, protocol_id);
+ }
mutex_unlock(&ni->pending_mtx);
}

static void scmi_put_active_handler(struct scmi_notify_instance *ni,
struct scmi_event_handler *hndl)
{
+ bool freed;
struct scmi_registered_event *r_evt = hndl->r_evt;
+ u8 protocol_id = r_evt->proto->id;

mutex_lock(&r_evt->proto->registered_mtx);
- scmi_put_handler_unlocked(ni, hndl);
+ freed = scmi_put_handler_unlocked(ni, hndl);
mutex_unlock(&r_evt->proto->registered_mtx);
+ if (freed)
+ scmi_release_protocol(ni->handle, protocol_id);
}

/**
--
2.17.1
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