[PATCH v6 05/37] firmware: arm_scmi: make notifications aware of protocols users

Cristian Marussi
2021-02-02T22:18:25Z

Account for any active registered notifier against the proper related
protocol; do not consider pending event handlers, only active handlers
will concur to protocol usage accounting.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
---
drivers/firmware/arm_scmi/notify.c | 51 ++++++++++++++++++++++++++----
1 file changed, 44 insertions(+), 7 deletions(-)

diff --git a/drivers/firmware/arm_scmi/notify.c b/drivers/firmware/arm_scmi/notify.c
index 66196b293b6c..cdaf0f962d84 100644
--- a/drivers/firmware/arm_scmi/notify.c
+++ b/drivers/firmware/arm_scmi/notify.c
@@ -91,6 +91,7 @@
#include <linux/types.h>
#include <linux/workqueue.h>

+#include "common.h"
#include "notify.h"

#define SCMI_MAX_PROTO 256
@@ -368,7 +369,7 @@ 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);

/**
@@ -900,9 +901,21 @@ 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);
@@ -1193,41 +1206,65 @@ 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