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 // SPDX-License-Identifier: GPL-2.0
 /*
  * System Control and Management Interface (SCMI) Notification support
  *
  * Copyright (C) 2020-2021 ARM Ltd.
  */
 /**
  * DOC: Theory of operation
  *
  * SCMI Protocol specification allows the platform to signal events to
  * interested agents via notification messages: this is an implementation
  * of the dispatch and delivery of such notifications to the interested users
  * inside the Linux kernel.
  *
  * An SCMI Notification core instance is initialized for each active platform
  * instance identified by the means of the usual &struct scmi_handle.
  *
  * Each SCMI Protocol implementation, during its initialization, registers with
  * this core its set of supported events using scmi_register_protocol_events():
  * all the needed descriptors are stored in the &struct registered_protocols and
  * &struct registered_events arrays.
  *
  * Kernel users interested in some specific event can register their callbacks
  * providing the usual notifier_block descriptor, since this core implements
  * events' delivery using the standard Kernel notification chains machinery.
  *
  * Given the number of possible events defined by SCMI and the extensibility
  * of the SCMI Protocol itself, the underlying notification chains are created
  * and destroyed dynamically on demand depending on the number of users
  * effectively registered for an event, so that no support structures or chains
  * are allocated until at least one user has registered a notifier_block for
  * such event. Similarly, events' generation itself is enabled at the platform
  * level only after at least one user has registered, and it is shutdown after
  * the last user for that event has gone.
  *
  * All users provided callbacks and allocated notification-chains are stored in
  * the @registered_events_handlers hashtable. Callbacks' registration requests
  * for still to be registered events are instead kept in the dedicated common
  * hashtable @pending_events_handlers.
  *
  * An event is identified univocally by the tuple (proto_id, evt_id, src_id)
  * and is served by its own dedicated notification chain; information contained
  * in such tuples is used, in a few different ways, to generate the needed
  * hash-keys.
  *
  * Here proto_id and evt_id are simply the protocol_id and message_id numbers
  * as described in the SCMI Protocol specification, while src_id represents an
  * optional, protocol dependent, source identifier (like domain_id, perf_id
  * or sensor_id and so forth).
  *
  * Upon reception of a notification message from the platform the SCMI RX ISR
  * passes the received message payload and some ancillary information (including
  * an arrival timestamp in nanoseconds) to the core via @scmi_notify() which
  * pushes the event-data itself on a protocol-dedicated kfifo queue for further
  * deferred processing as specified in @scmi_events_dispatcher().
  *
  * Each protocol has it own dedicated work_struct and worker which, once kicked
  * by the ISR, takes care to empty its own dedicated queue, deliverying the
  * queued items into the proper notification-chain: notifications processing can
  * proceed concurrently on distinct workers only between events belonging to
  * different protocols while delivery of events within the same protocol is
  * still strictly sequentially ordered by time of arrival.
  *
  * Events' information is then extracted from the SCMI Notification messages and
  * conveyed, converted into a custom per-event report struct, as the void *data
  * param to the user callback provided by the registered notifier_block, so that
  * from the user perspective his callback will look invoked like:
  *
  * int user_cb(struct notifier_block *nb, unsigned long event_id, void *report)
  *
  */
 
 #define dev_fmt(fmt) "SCMI Notifications - " fmt
 #define pr_fmt(fmt) "SCMI Notifications - " fmt
 
 #include <linux/bitfield.h>
 #include <linux/bug.h>
 #include <linux/compiler.h>
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/hashtable.h>
 #include <linux/kernel.h>
 #include <linux/ktime.h>
 #include <linux/kfifo.h>
 #include <linux/list.h>
 #include <linux/mutex.h>
 #include <linux/notifier.h>
 #include <linux/refcount.h>
 #include <linux/scmi_protocol.h>
 #include <linux/slab.h>
 #include <linux/types.h>
 #include <linux/workqueue.h>
 
 #include "common.h"
 #include "notify.h"
 
 #define SCMI_MAX_PROTO      256
 
 #define PROTO_ID_MASK       GENMASK(31, 24)
 #define EVT_ID_MASK     GENMASK(23, 16)
 #define SRC_ID_MASK     GENMASK(15, 0)
 
 /*
  * Builds an unsigned 32bit key from the given input tuple to be used
  * as a key in hashtables.
  */
 #define MAKE_HASH_KEY(p, e, s)          \
     (FIELD_PREP(PROTO_ID_MASK, (p)) |   \
        FIELD_PREP(EVT_ID_MASK, (e)) |   \
        FIELD_PREP(SRC_ID_MASK, (s)))
 
 #define MAKE_ALL_SRCS_KEY(p, e)     MAKE_HASH_KEY((p), (e), SRC_ID_MASK)
 
 /*
  * Assumes that the stored obj includes its own hash-key in a field named 'key':
  * with this simplification this macro can be equally used for all the objects'
  * types hashed by this implementation.
  *
  * @__ht: The hashtable name
  * @__obj: A pointer to the object type to be retrieved from the hashtable;
  *     it will be used as a cursor while scanning the hastable and it will
  *     be possibly left as NULL when @__k is not found
  * @__k: The key to search for
  */
 #define KEY_FIND(__ht, __obj, __k)              \
 ({                              \
     typeof(__k) k_ = __k;                   \
     typeof(__obj) obj_;                 \
                                 \
     hash_for_each_possible((__ht), obj_, hash, k_)      \
         if (obj_->key == k_)                \
             break;                  \
     __obj = obj_;                       \
 })
 
 #define KEY_XTRACT_PROTO_ID(key)    FIELD_GET(PROTO_ID_MASK, (key))
 #define KEY_XTRACT_EVT_ID(key)      FIELD_GET(EVT_ID_MASK, (key))
 #define KEY_XTRACT_SRC_ID(key)      FIELD_GET(SRC_ID_MASK, (key))
 
 /*
  * A set of macros used to access safely @registered_protocols and
  * @registered_events arrays; these are fixed in size and each entry is possibly
  * populated at protocols' registration time and then only read but NEVER
  * modified or removed.
  */
 #define SCMI_GET_PROTO(__ni, __pid)                 \
 ({                                  \
     typeof(__ni) ni_ = __ni;                    \
     struct scmi_registered_events_desc *__pd = NULL;        \
                                     \
     if (ni_)                            \
         __pd = READ_ONCE(ni_->registered_protocols[(__pid)]);   \
     __pd;                               \
 })
 
 #define SCMI_GET_REVT_FROM_PD(__pd, __eid)              \
 ({                                  \
     typeof(__pd) pd_ = __pd;                    \
     typeof(__eid) eid_ = __eid;                 \
     struct scmi_registered_event *__revt = NULL;            \
                                     \
     if (pd_ && eid_ < pd_->num_events)              \
         __revt = READ_ONCE(pd_->registered_events[eid_]);   \
     __revt;                             \
 })
 
 #define SCMI_GET_REVT(__ni, __pid, __eid)               \
 ({                                  \
     struct scmi_registered_event *__revt;               \
     struct scmi_registered_events_desc *__pd;           \
                                     \
     __pd = SCMI_GET_PROTO((__ni), (__pid));             \
     __revt = SCMI_GET_REVT_FROM_PD(__pd, (__eid));          \
     __revt;                             \
 })
 
 /* A couple of utility macros to limit cruft when calling protocols' helpers */
 #define REVT_NOTIFY_SET_STATUS(revt, eid, sid, state)       \
 ({                              \
     typeof(revt) r = revt;                  \
     r->proto->ops->set_notify_enabled(r->proto->ph,     \
                     (eid), (sid), (state)); \
 })
 
 #define REVT_NOTIFY_ENABLE(revt, eid, sid)          \
     REVT_NOTIFY_SET_STATUS((revt), (eid), (sid), true)
 
 #define REVT_NOTIFY_DISABLE(revt, eid, sid)         \
     REVT_NOTIFY_SET_STATUS((revt), (eid), (sid), false)
 
 #define REVT_FILL_REPORT(revt, ...)             \
 ({                              \
     typeof(revt) r = revt;                  \
     r->proto->ops->fill_custom_report(r->proto->ph,     \
                       __VA_ARGS__);     \
 })
 
 #define SCMI_PENDING_HASH_SZ        4
 #define SCMI_REGISTERED_HASH_SZ     6
 
 struct scmi_registered_events_desc;
 
 /**
  * struct scmi_notify_instance  - Represents an instance of the notification
  * core
  * @gid: GroupID used for devres
  * @handle: A reference to the platform instance
  * @init_work: A work item to perform final initializations of pending handlers
  * @notify_wq: A reference to the allocated Kernel cmwq
  * @pending_mtx: A mutex to protect @pending_events_handlers
  * @registered_protocols: A statically allocated array containing pointers to
  *            all the registered protocol-level specific information
  *            related to events' handling
  * @pending_events_handlers: An hashtable containing all pending events'
  *               handlers descriptors
  *
  * Each platform instance, represented by a handle, has its own instance of
  * the notification subsystem represented by this structure.
  */
 struct scmi_notify_instance {
     void            *gid;
     struct scmi_handle  *handle;
     struct work_struct  init_work;
     struct workqueue_struct *notify_wq;
     /* lock to protect pending_events_handlers */
     struct mutex        pending_mtx;
     struct scmi_registered_events_desc  **registered_protocols;
     DECLARE_HASHTABLE(pending_events_handlers, SCMI_PENDING_HASH_SZ);
 };
 
 /**
  * struct events_queue  - Describes a queue and its associated worker
  * @sz: Size in bytes of the related kfifo
  * @kfifo: A dedicated Kernel kfifo descriptor
  * @notify_work: A custom work item bound to this queue
  * @wq: A reference to the associated workqueue
  *
  * Each protocol has its own dedicated events_queue descriptor.
  */
 struct events_queue {
     size_t          sz;
     struct kfifo        kfifo;
     struct work_struct  notify_work;
     struct workqueue_struct *wq;
 };
 
 /**
  * struct scmi_event_header  - A utility header
  * @timestamp: The timestamp, in nanoseconds (boottime), which was associated
  *         to this event as soon as it entered the SCMI RX ISR
  * @payld_sz: Effective size of the embedded message payload which follows
  * @evt_id: Event ID (corresponds to the Event MsgID for this Protocol)
  * @payld: A reference to the embedded event payload
  *
  * This header is prepended to each received event message payload before
  * queueing it on the related &struct events_queue.
  */
 struct scmi_event_header {
     ktime_t timestamp;
     size_t payld_sz;
     unsigned char evt_id;
     unsigned char payld[];
 };
 
 struct scmi_registered_event;
 
 /**
  * struct scmi_registered_events_desc  - Protocol Specific information
  * @id: Protocol ID
  * @ops: Protocol specific and event-related operations
  * @equeue: The embedded per-protocol events_queue
  * @ni: A reference to the initialized instance descriptor
  * @eh: A reference to pre-allocated buffer to be used as a scratch area by the
  *  deferred worker when fetching data from the kfifo
  * @eh_sz: Size of the pre-allocated buffer @eh
  * @in_flight: A reference to an in flight &struct scmi_registered_event
  * @num_events: Number of events in @registered_events
  * @registered_events: A dynamically allocated array holding all the registered
  *             events' descriptors, whose fixed-size is determined at
  *             compile time.
  * @registered_mtx: A mutex to protect @registered_events_handlers
  * @ph: SCMI protocol handle reference
  * @registered_events_handlers: An hashtable containing all events' handlers
  *              descriptors registered for this protocol
  *
  * All protocols that register at least one event have their protocol-specific
  * information stored here, together with the embedded allocated events_queue.
  * These descriptors are stored in the @registered_protocols array at protocol
  * registration time.
  *
  * Once these descriptors are successfully registered, they are NEVER again
  * removed or modified since protocols do not unregister ever, so that, once
  * we safely grab a NON-NULL reference from the array we can keep it and use it.
  */
 struct scmi_registered_events_desc {
     u8              id;
     const struct scmi_event_ops *ops;
     struct events_queue     equeue;
     struct scmi_notify_instance *ni;
     struct scmi_event_header    *eh;
     size_t              eh_sz;
     void                *in_flight;
     int             num_events;
     struct scmi_registered_event    **registered_events;
     /* mutex to protect registered_events_handlers */
     struct mutex            registered_mtx;
     const struct scmi_protocol_handle   *ph;
     DECLARE_HASHTABLE(registered_events_handlers, SCMI_REGISTERED_HASH_SZ);
 };
 
 /**
  * struct scmi_registered_event  - Event Specific Information
  * @proto: A reference to the associated protocol descriptor
  * @evt: A reference to the associated event descriptor (as provided at
  *       registration time)
  * @report: A pre-allocated buffer used by the deferred worker to fill a
  *      customized event report
  * @num_sources: The number of possible sources for this event as stated at
  *       events' registration time
  * @sources: A reference to a dynamically allocated array used to refcount the
  *       events' enable requests for all the existing sources
  * @sources_mtx: A mutex to serialize the access to @sources
  *
  * All registered events are represented by one of these structures that are
  * stored in the @registered_events array at protocol registration time.
  *
  * Once these descriptors are successfully registered, they are NEVER again
  * removed or modified since protocols do not unregister ever, so that once we
  * safely grab a NON-NULL reference from the table we can keep it and use it.
  */
 struct scmi_registered_event {
     struct scmi_registered_events_desc *proto;
     const struct scmi_event *evt;
     void        *report;
     u32     num_sources;
     refcount_t  *sources;
     /* locking to serialize the access to sources */
     struct mutex    sources_mtx;
 };
 
 /**
  * struct scmi_event_handler  - Event handler information
  * @key: The used hashkey
  * @users: A reference count for number of active users for this handler
  * @r_evt: A reference to the associated registered event; when this is NULL
  *     this handler is pending, which means that identifies a set of
  *     callbacks intended to be attached to an event which is still not
  *     known nor registered by any protocol at that point in time
  * @chain: The notification chain dedicated to this specific event tuple
  * @hash: The hlist_node used for collision handling
  * @enabled: A boolean which records if event's generation has been already
  *       enabled for this handler as a whole
  *
  * This structure collects all the information needed to process a received
  * event identified by the tuple (proto_id, evt_id, src_id).
  * These descriptors are stored in a per-protocol @registered_events_handlers
  * table using as a key a value derived from that tuple.
  */
 struct scmi_event_handler {
     u32             key;
     refcount_t          users;
     struct scmi_registered_event    *r_evt;
     struct blocking_notifier_head   chain;
     struct hlist_node       hash;
     bool                enabled;
 };
 
 #define IS_HNDL_PENDING(hndl)   (!(hndl)->r_evt)
 
 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 bool scmi_put_handler_unlocked(struct scmi_notify_instance *ni,
                       struct scmi_event_handler *hndl);
 
 /**
  * scmi_lookup_and_call_event_chain()  - Lookup the proper chain and call it
  * @ni: A reference to the notification instance to use
  * @evt_key: The key to use to lookup the related notification chain
  * @report: The customized event-specific report to pass down to the callbacks
  *      as their *data parameter.
  */
 static inline void
 scmi_lookup_and_call_event_chain(struct scmi_notify_instance *ni,
                  u32 evt_key, void *report)
 {
     int ret;
     struct scmi_event_handler *hndl;
 
     /*
      * Here ensure the event handler cannot vanish while using it.
      * It is legitimate, though, for an handler not to be found at all here,
      * e.g. when it has been unregistered by the user after some events had
      * already been queued.
      */
     hndl = scmi_get_active_handler(ni, evt_key);
     if (!hndl)
         return;
 
     ret = blocking_notifier_call_chain(&hndl->chain,
                        KEY_XTRACT_EVT_ID(evt_key),
                        report);
     /* Notifiers are NOT supposed to cut the chain ... */
     WARN_ON_ONCE(ret & NOTIFY_STOP_MASK);
 
     scmi_put_active_handler(ni, hndl);
 }
 
 /**
  * scmi_process_event_header()  - Dequeue and process an event header
  * @eq: The queue to use
  * @pd: The protocol descriptor to use
  *
  * Read an event header from the protocol queue into the dedicated scratch
  * buffer and looks for a matching registered event; in case an anomalously
  * sized read is detected just flush the queue.
  *
  * Return:
  * * a reference to the matching registered event when found
  * * ERR_PTR(-EINVAL) when NO registered event could be found
  * * NULL when the queue is empty
  */
 static inline struct scmi_registered_event *
 scmi_process_event_header(struct events_queue *eq,
               struct scmi_registered_events_desc *pd)
 {
     unsigned int outs;
     struct scmi_registered_event *r_evt;
 
     outs = kfifo_out(&eq->kfifo, pd->eh,
              sizeof(struct scmi_event_header));
     if (!outs)
         return NULL;
     if (outs != sizeof(struct scmi_event_header)) {
         dev_err(pd->ni->handle->dev, "corrupted EVT header. Flush.\n");
         kfifo_reset_out(&eq->kfifo);
         return NULL;
     }
 
     r_evt = SCMI_GET_REVT_FROM_PD(pd, pd->eh->evt_id);
     if (!r_evt)
         r_evt = ERR_PTR(-EINVAL);
 
     return r_evt;
 }
 
 /**
  * scmi_process_event_payload()  - Dequeue and process an event payload
  * @eq: The queue to use
  * @pd: The protocol descriptor to use
  * @r_evt: The registered event descriptor to use
  *
  * Read an event payload from the protocol queue into the dedicated scratch
  * buffer, fills a custom report and then look for matching event handlers and
  * call them; skip any unknown event (as marked by scmi_process_event_header())
  * and in case an anomalously sized read is detected just flush the queue.
  *
  * Return: False when the queue is empty
  */
 static inline bool
 scmi_process_event_payload(struct events_queue *eq,
                struct scmi_registered_events_desc *pd,
                struct scmi_registered_event *r_evt)
 {
     u32 src_id, key;
     unsigned int outs;
     void *report = NULL;
 
     outs = kfifo_out(&eq->kfifo, pd->eh->payld, pd->eh->payld_sz);
     if (!outs)
         return false;
 
     /* Any in-flight event has now been officially processed */
     pd->in_flight = NULL;
 
     if (outs != pd->eh->payld_sz) {
         dev_err(pd->ni->handle->dev, "corrupted EVT Payload. Flush.\n");
         kfifo_reset_out(&eq->kfifo);
         return false;
     }
 
     if (IS_ERR(r_evt)) {
         dev_warn(pd->ni->handle->dev,
              "SKIP UNKNOWN EVT - proto:%X  evt:%d\n",
              pd->id, pd->eh->evt_id);
         return true;
     }
 
     report = REVT_FILL_REPORT(r_evt, pd->eh->evt_id, pd->eh->timestamp,
                   pd->eh->payld, pd->eh->payld_sz,
                   r_evt->report, &src_id);
     if (!report) {
         dev_err(pd->ni->handle->dev,
             "report not available - proto:%X  evt:%d\n",
             pd->id, pd->eh->evt_id);
         return true;
     }
 
     /* At first search for a generic ALL src_ids handler... */
     key = MAKE_ALL_SRCS_KEY(pd->id, pd->eh->evt_id);
     scmi_lookup_and_call_event_chain(pd->ni, key, report);
 
     /* ...then search for any specific src_id */
     key = MAKE_HASH_KEY(pd->id, pd->eh->evt_id, src_id);
     scmi_lookup_and_call_event_chain(pd->ni, key, report);
 
     return true;
 }
 
 /**
  * scmi_events_dispatcher()  - Common worker logic for all work items.
  * @work: The work item to use, which is associated to a dedicated events_queue
  *
  * Logic:
  *  1. dequeue one pending RX notification (queued in SCMI RX ISR context)
  *  2. generate a custom event report from the received event message
  *  3. lookup for any registered ALL_SRC_IDs handler:
  *    - > call the related notification chain passing in the report
  *  4. lookup for any registered specific SRC_ID handler:
  *    - > call the related notification chain passing in the report
  *
  * Note that:
  * * a dedicated per-protocol kfifo queue is used: in this way an anomalous
  *   flood of events cannot saturate other protocols' queues.
  * * each per-protocol queue is associated to a distinct work_item, which
  *   means, in turn, that:
  *   + all protocols can process their dedicated queues concurrently
  *     (since notify_wq:max_active != 1)
  *   + anyway at most one worker instance is allowed to run on the same queue
  *     concurrently: this ensures that we can have only one concurrent
  *     reader/writer on the associated kfifo, so that we can use it lock-less
  *
  * Context: Process context.
  */
 static void scmi_events_dispatcher(struct work_struct *work)
 {
     struct events_queue *eq;
     struct scmi_registered_events_desc *pd;
     struct scmi_registered_event *r_evt;
 
     eq = container_of(work, struct events_queue, notify_work);
     pd = container_of(eq, struct scmi_registered_events_desc, equeue);
     /*
      * In order to keep the queue lock-less and the number of memcopies
      * to the bare minimum needed, the dispatcher accounts for the
      * possibility of per-protocol in-flight events: i.e. an event whose
      * reception could end up being split across two subsequent runs of this
      * worker, first the header, then the payload.
      */
     do {
         if (!pd->in_flight) {
             r_evt = scmi_process_event_header(eq, pd);
             if (!r_evt)
                 break;
             pd->in_flight = r_evt;
         } else {
             r_evt = pd->in_flight;
         }
     } while (scmi_process_event_payload(eq, pd, r_evt));
 }
 
 /**
  * scmi_notify()  - Queues a notification for further deferred processing
  * @handle: The handle identifying the platform instance from which the
  *      dispatched event is generated
  * @proto_id: Protocol ID
  * @evt_id: Event ID (msgID)
  * @buf: Event Message Payload (without the header)
  * @len: Event Message Payload size
  * @ts: RX Timestamp in nanoseconds (boottime)
  *
  * Context: Called in interrupt context to queue a received event for
  * deferred processing.
  *
  * Return: 0 on Success
  */
 int scmi_notify(const struct scmi_handle *handle, u8 proto_id, u8 evt_id,
         const void *buf, size_t len, ktime_t ts)
 {
     struct scmi_registered_event *r_evt;
     struct scmi_event_header eh;
     struct scmi_notify_instance *ni;
 
     ni = scmi_notification_instance_data_get(handle);
     if (!ni)
         return 0;
 
     r_evt = SCMI_GET_REVT(ni, proto_id, evt_id);
     if (!r_evt)
         return -EINVAL;
 
     if (len > r_evt->evt->max_payld_sz) {
         dev_err(handle->dev, "discard badly sized message\n");
         return -EINVAL;
     }
     if (kfifo_avail(&r_evt->proto->equeue.kfifo) < sizeof(eh) + len) {
         dev_warn(handle->dev,
              "queue full, dropping proto_id:%d  evt_id:%d  ts:%lld\n",
              proto_id, evt_id, ktime_to_ns(ts));
         return -ENOMEM;
     }
 
     eh.timestamp = ts;
     eh.evt_id = evt_id;
     eh.payld_sz = len;
     /*
      * Header and payload are enqueued with two distinct kfifo_in() (so non
      * atomic), but this situation is handled properly on the consumer side
      * with in-flight events tracking.
      */
     kfifo_in(&r_evt->proto->equeue.kfifo, &eh, sizeof(eh));
     kfifo_in(&r_evt->proto->equeue.kfifo, buf, len);
     /*
      * Don't care about return value here since we just want to ensure that
      * a work is queued all the times whenever some items have been pushed
      * on the kfifo:
      * - if work was already queued it will simply fail to queue a new one
      *   since it is not needed
      * - if work was not queued already it will be now, even in case work
      *   was in fact already running: this behavior avoids any possible race
      *   when this function pushes new items onto the kfifos after the
      *   related executing worker had already determined the kfifo to be
      *   empty and it was terminating.
      */
     queue_work(r_evt->proto->equeue.wq,
            &r_evt->proto->equeue.notify_work);
 
     return 0;
 }
 
 /**
  * scmi_kfifo_free()  - Devres action helper to free the kfifo
  * @kfifo: The kfifo to free
  */
 static void scmi_kfifo_free(void *kfifo)
 {
     kfifo_free((struct kfifo *)kfifo);
 }
 
 /**
  * scmi_initialize_events_queue()  - Allocate/Initialize a kfifo buffer
  * @ni: A reference to the notification instance to use
  * @equeue: The events_queue to initialize
  * @sz: Size of the kfifo buffer to allocate
  *
  * Allocate a buffer for the kfifo and initialize it.
  *
  * Return: 0 on Success
  */
 static int scmi_initialize_events_queue(struct scmi_notify_instance *ni,
                     struct events_queue *equeue, size_t sz)
 {
     int ret;
 
     if (kfifo_alloc(&equeue->kfifo, sz, GFP_KERNEL))
         return -ENOMEM;
     /* Size could have been roundup to power-of-two */
     equeue->sz = kfifo_size(&equeue->kfifo);
 
     ret = devm_add_action_or_reset(ni->handle->dev, scmi_kfifo_free,
                        &equeue->kfifo);
     if (ret)
         return ret;
 
     INIT_WORK(&equeue->notify_work, scmi_events_dispatcher);
     equeue->wq = ni->notify_wq;
 
     return ret;
 }
 
 /**
  * scmi_allocate_registered_events_desc()  - Allocate a registered events'
  * descriptor
  * @ni: A reference to the &struct scmi_notify_instance notification instance
  *  to use
  * @proto_id: Protocol ID
  * @queue_sz: Size of the associated queue to allocate
  * @eh_sz: Size of the event header scratch area to pre-allocate
  * @num_events: Number of events to support (size of @registered_events)
  * @ops: Pointer to a struct holding references to protocol specific helpers
  *   needed during events handling
  *
  * It is supposed to be called only once for each protocol at protocol
  * initialization time, so it warns if the requested protocol is found already
  * registered.
  *
  * Return: The allocated and registered descriptor on Success
  */
 static struct scmi_registered_events_desc *
 scmi_allocate_registered_events_desc(struct scmi_notify_instance *ni,
                      u8 proto_id, size_t queue_sz, size_t eh_sz,
                      int num_events,
                      const struct scmi_event_ops *ops)
 {
     int ret;
     struct scmi_registered_events_desc *pd;
 
     /* Ensure protocols are up to date */
     smp_rmb();
     if (WARN_ON(ni->registered_protocols[proto_id]))
         return ERR_PTR(-EINVAL);
 
     pd = devm_kzalloc(ni->handle->dev, sizeof(*pd), GFP_KERNEL);
     if (!pd)
         return ERR_PTR(-ENOMEM);
     pd->id = proto_id;
     pd->ops = ops;
     pd->ni = ni;
 
     ret = scmi_initialize_events_queue(ni, &pd->equeue, queue_sz);
     if (ret)
         return ERR_PTR(ret);
 
     pd->eh = devm_kzalloc(ni->handle->dev, eh_sz, GFP_KERNEL);
     if (!pd->eh)
         return ERR_PTR(-ENOMEM);
     pd->eh_sz = eh_sz;
 
     pd->registered_events = devm_kcalloc(ni->handle->dev, num_events,
                          sizeof(char *), GFP_KERNEL);
     if (!pd->registered_events)
         return ERR_PTR(-ENOMEM);
     pd->num_events = num_events;
 
     /* Initialize per protocol handlers table */
     mutex_init(&pd->registered_mtx);
     hash_init(pd->registered_events_handlers);
 
     return pd;
 }
 
 /**
  * scmi_register_protocol_events()  - Register Protocol Events with the core
  * @handle: The handle identifying the platform instance against which the
  *      protocol's events are registered
  * @proto_id: Protocol ID
  * @ph: SCMI protocol handle.
  * @ee: A structure describing the events supported by this protocol.
  *
  * Used by SCMI Protocols initialization code to register with the notification
  * core the list of supported events and their descriptors: takes care to
  * pre-allocate and store all needed descriptors, scratch buffers and event
  * queues.
  *
  * Return: 0 on Success
  */
 int scmi_register_protocol_events(const struct scmi_handle *handle, u8 proto_id,
                   const struct scmi_protocol_handle *ph,
                   const struct scmi_protocol_events *ee)
 {
     int i;
     unsigned int num_sources;
     size_t payld_sz = 0;
     struct scmi_registered_events_desc *pd;
     struct scmi_notify_instance *ni;
     const struct scmi_event *evt;
 
     if (!ee || !ee->ops || !ee->evts || !ph ||
         (!ee->num_sources && !ee->ops->get_num_sources))
         return -EINVAL;
 
     ni = scmi_notification_instance_data_get(handle);
     if (!ni)
         return -ENOMEM;
 
     /* num_sources cannot be <= 0 */
     if (ee->num_sources) {
         num_sources = ee->num_sources;
     } else {
         int nsrc = ee->ops->get_num_sources(ph);
 
         if (nsrc <= 0)
             return -EINVAL;
         num_sources = nsrc;
     }
 
     evt = ee->evts;
     for (i = 0; i < ee->num_events; i++)
         payld_sz = max_t(size_t, payld_sz, evt[i].max_payld_sz);
     payld_sz += sizeof(struct scmi_event_header);
 
     pd = scmi_allocate_registered_events_desc(ni, proto_id, ee->queue_sz,
                           payld_sz, ee->num_events,
                           ee->ops);
     if (IS_ERR(pd))
         return PTR_ERR(pd);
 
     pd->ph = ph;
     for (i = 0; i < ee->num_events; i++, evt++) {
         struct scmi_registered_event *r_evt;
 
         r_evt = devm_kzalloc(ni->handle->dev, sizeof(*r_evt),
                      GFP_KERNEL);
         if (!r_evt)
             return -ENOMEM;
         r_evt->proto = pd;
         r_evt->evt = evt;
 
         r_evt->sources = devm_kcalloc(ni->handle->dev, num_sources,
                           sizeof(refcount_t), GFP_KERNEL);
         if (!r_evt->sources)
             return -ENOMEM;
         r_evt->num_sources = num_sources;
         mutex_init(&r_evt->sources_mtx);
 
         r_evt->report = devm_kzalloc(ni->handle->dev,
                          evt->max_report_sz, GFP_KERNEL);
         if (!r_evt->report)
             return -ENOMEM;
 
         pd->registered_events[i] = r_evt;
         /* Ensure events are updated */
         smp_wmb();
         dev_dbg(handle->dev, "registered event - %lX\n",
             MAKE_ALL_SRCS_KEY(r_evt->proto->id, r_evt->evt->id));
     }
 
     /* Register protocol and events...it will never be removed */
     ni->registered_protocols[proto_id] = pd;
     /* Ensure protocols are updated */
     smp_wmb();
 
     /*
      * Finalize any pending events' handler which could have been waiting
      * for this protocol's events registration.
      */
     schedule_work(&ni->init_work);
 
     return 0;
 }
 
 /**
  * scmi_deregister_protocol_events  - Deregister protocol events with the core
  * @handle: The handle identifying the platform instance against which the
  *      protocol's events are registered
  * @proto_id: Protocol ID
  */
 void scmi_deregister_protocol_events(const struct scmi_handle *handle,
                      u8 proto_id)
 {
     struct scmi_notify_instance *ni;
     struct scmi_registered_events_desc *pd;
 
     ni = scmi_notification_instance_data_get(handle);
     if (!ni)
         return;
 
     pd = ni->registered_protocols[proto_id];
     if (!pd)
         return;
 
     ni->registered_protocols[proto_id] = NULL;
     /* Ensure protocols are updated */
     smp_wmb();
 
     cancel_work_sync(&pd->equeue.notify_work);
 }
 
 /**
  * scmi_allocate_event_handler()  - Allocate Event handler
  * @ni: A reference to the notification instance to use
  * @evt_key: 32bit key uniquely bind to the event identified by the tuple
  *       (proto_id, evt_id, src_id)
  *
  * Allocate an event handler and related notification chain associated with
  * the provided event handler key.
  * Note that, at this point, a related registered_event is still to be
  * associated to this handler descriptor (hndl->r_evt == NULL), so the handler
  * is initialized as pending.
  *
  * Context: Assumes to be called with @pending_mtx already acquired.
  * Return: the freshly allocated structure on Success
  */
 static struct scmi_event_handler *
 scmi_allocate_event_handler(struct scmi_notify_instance *ni, u32 evt_key)
 {
     struct scmi_event_handler *hndl;
 
     hndl = kzalloc(sizeof(*hndl), GFP_KERNEL);
     if (!hndl)
         return NULL;
     hndl->key = evt_key;
     BLOCKING_INIT_NOTIFIER_HEAD(&hndl->chain);
     refcount_set(&hndl->users, 1);
     /* New handlers are created pending */
     hash_add(ni->pending_events_handlers, &hndl->hash, hndl->key);
 
     return hndl;
 }
 
 /**
  * scmi_free_event_handler()  - Free the provided Event handler
  * @hndl: The event handler structure to free
  *
  * Context: Assumes to be called with proper locking acquired depending
  *      on the situation.
  */
 static void scmi_free_event_handler(struct scmi_event_handler *hndl)
 {
     hash_del(&hndl->hash);
     kfree(hndl);
 }
 
 /**
  * scmi_bind_event_handler()  - Helper to attempt binding an handler to an event
  * @ni: A reference to the notification instance to use
  * @hndl: The event handler to bind
  *
  * If an associated registered event is found, move the handler from the pending
  * into the registered table.
  *
  * Context: Assumes to be called with @pending_mtx already acquired.
  *
  * Return: 0 on Success
  */
 static inline int scmi_bind_event_handler(struct scmi_notify_instance *ni,
                       struct scmi_event_handler *hndl)
 {
     struct scmi_registered_event *r_evt;
 
     r_evt = SCMI_GET_REVT(ni, KEY_XTRACT_PROTO_ID(hndl->key),
                   KEY_XTRACT_EVT_ID(hndl->key));
     if (!r_evt)
         return -EINVAL;
 
     /*
      * 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_protocol_acquire(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);
     mutex_unlock(&r_evt->proto->registered_mtx);
 
     return 0;
 }
 
 /**
  * scmi_valid_pending_handler()  - Helper to check pending status of handlers
  * @ni: A reference to the notification instance to use
  * @hndl: The event handler to check
  *
  * An handler is considered pending when its r_evt == NULL, because the related
  * event was still unknown at handler's registration time; anyway, since all
  * protocols register their supported events once for all at protocols'
  * initialization time, a pending handler cannot be considered valid anymore if
  * the underlying event (which it is waiting for), belongs to an already
  * initialized and registered protocol.
  *
  * Return: 0 on Success
  */
 static inline int scmi_valid_pending_handler(struct scmi_notify_instance *ni,
                          struct scmi_event_handler *hndl)
 {
     struct scmi_registered_events_desc *pd;
 
     if (!IS_HNDL_PENDING(hndl))
         return -EINVAL;
 
     pd = SCMI_GET_PROTO(ni, KEY_XTRACT_PROTO_ID(hndl->key));
     if (pd)
         return -EINVAL;
 
     return 0;
 }
 
 /**
  * scmi_register_event_handler()  - Register whenever possible an Event handler
  * @ni: A reference to the notification instance to use
  * @hndl: The event handler to register
  *
  * At first try to bind an event handler to its associated event, then check if
  * it was at least a valid pending handler: if it was not bound nor valid return
  * false.
  *
  * Valid pending incomplete bindings will be periodically retried by a dedicated
  * worker which is kicked each time a new protocol completes its own
  * registration phase.
  *
  * Context: Assumes to be called with @pending_mtx acquired.
  *
  * Return: 0 on Success
  */
 static int scmi_register_event_handler(struct scmi_notify_instance *ni,
                        struct scmi_event_handler *hndl)
 {
     int ret;
 
     ret = scmi_bind_event_handler(ni, hndl);
     if (!ret) {
         dev_dbg(ni->handle->dev, "registered NEW handler - key:%X\n",
             hndl->key);
     } else {
         ret = scmi_valid_pending_handler(ni, hndl);
         if (!ret)
             dev_dbg(ni->handle->dev,
                 "registered PENDING handler - key:%X\n",
                 hndl->key);
     }
 
     return ret;
 }
 
 /**
  * __scmi_event_handler_get_ops()  - Utility to get or create an event handler
  * @ni: A reference to the notification instance to use
  * @evt_key: The event key to use
  * @create: A boolean flag to specify if a handler must be created when
  *      not already existent
  *
  * Search for the desired handler matching the key in both the per-protocol
  * registered table and the common pending table:
  * * if found adjust users refcount
  * * if not found and @create is true, create and register the new handler:
  *   handler could end up being registered as pending if no matching event
  *   could be found.
  *
  * An handler is guaranteed to reside in one and only one of the tables at
  * any one time; to ensure this the whole search and create is performed
  * holding the @pending_mtx lock, with @registered_mtx additionally acquired
  * if needed.
  *
  * Note that when a nested acquisition of these mutexes is needed the locking
  * order is always (same as in @init_work):
  * 1. pending_mtx
  * 2. registered_mtx
  *
  * Events generation is NOT enabled right after creation within this routine
  * since at creation time we usually want to have all setup and ready before
  * events really start flowing.
  *
  * Return: A properly refcounted handler on Success, NULL on Failure
  */
 static inline struct scmi_event_handler *
 __scmi_event_handler_get_ops(struct scmi_notify_instance *ni,
                  u32 evt_key, bool create)
 {
     struct scmi_registered_event *r_evt;
     struct scmi_event_handler *hndl = NULL;
 
     r_evt = SCMI_GET_REVT(ni, KEY_XTRACT_PROTO_ID(evt_key),
                   KEY_XTRACT_EVT_ID(evt_key));
 
     mutex_lock(&ni->pending_mtx);
     /* Search registered events at first ... if possible at all */
     if (r_evt) {
         mutex_lock(&r_evt->proto->registered_mtx);
         hndl = KEY_FIND(r_evt->proto->registered_events_handlers,
                 hndl, evt_key);
         if (hndl)
             refcount_inc(&hndl->users);
         mutex_unlock(&r_evt->proto->registered_mtx);
     }
 
     /* ...then amongst pending. */
     if (!hndl) {
         hndl = KEY_FIND(ni->pending_events_handlers, hndl, evt_key);
         if (hndl)
             refcount_inc(&hndl->users);
     }
 
     /* Create if still not found and required */
     if (!hndl && create) {
         hndl = scmi_allocate_event_handler(ni, evt_key);
         if (hndl && scmi_register_event_handler(ni, hndl)) {
             dev_dbg(ni->handle->dev,
                 "purging UNKNOWN handler - key:%X\n",
                 hndl->key);
             /* this hndl can be only a pending one */
             scmi_put_handler_unlocked(ni, hndl);
             hndl = NULL;
         }
     }
     mutex_unlock(&ni->pending_mtx);
 
     return hndl;
 }
 
 static struct scmi_event_handler *
 scmi_get_handler(struct scmi_notify_instance *ni, u32 evt_key)
 {
     return __scmi_event_handler_get_ops(ni, evt_key, false);
 }
 
 static struct scmi_event_handler *
 scmi_get_or_create_handler(struct scmi_notify_instance *ni, u32 evt_key)
 {
     return __scmi_event_handler_get_ops(ni, evt_key, true);
 }
 
 /**
  * scmi_get_active_handler()  - Helper to get active handlers only
  * @ni: A reference to the notification instance to use
  * @evt_key: The event key to use
  *
  * Search for the desired handler matching the key only in the per-protocol
  * table of registered handlers: this is called only from the dispatching path
  * so want to be as quick as possible and do not care about pending.
  *
  * Return: A properly refcounted active handler
  */
 static struct scmi_event_handler *
 scmi_get_active_handler(struct scmi_notify_instance *ni, u32 evt_key)
 {
     struct scmi_registered_event *r_evt;
     struct scmi_event_handler *hndl = NULL;
 
     r_evt = SCMI_GET_REVT(ni, KEY_XTRACT_PROTO_ID(evt_key),
                   KEY_XTRACT_EVT_ID(evt_key));
     if (r_evt) {
         mutex_lock(&r_evt->proto->registered_mtx);
         hndl = KEY_FIND(r_evt->proto->registered_events_handlers,
                 hndl, evt_key);
         if (hndl)
             refcount_inc(&hndl->users);
         mutex_unlock(&r_evt->proto->registered_mtx);
     }
 
     return hndl;
 }
 
 /**
  * __scmi_enable_evt()  - Enable/disable events generation
  * @r_evt: The registered event to act upon
  * @src_id: The src_id to act upon
  * @enable: The action to perform: true->Enable, false->Disable
  *
  * Takes care of proper refcounting while performing enable/disable: handles
  * the special case of ALL sources requests by itself.
  * Returns successfully if at least one of the required src_id has been
  * successfully enabled/disabled.
  *
  * Return: 0 on Success
  */
 static inline int __scmi_enable_evt(struct scmi_registered_event *r_evt,
                     u32 src_id, bool enable)
 {
     int retvals = 0;
     u32 num_sources;
     refcount_t *sid;
 
     if (src_id == SRC_ID_MASK) {
         src_id = 0;
         num_sources = r_evt->num_sources;
     } else if (src_id < r_evt->num_sources) {
         num_sources = 1;
     } else {
         return -EINVAL;
     }
 
     mutex_lock(&r_evt->sources_mtx);
     if (enable) {
         for (; num_sources; src_id++, num_sources--) {
             int ret = 0;
 
             sid = &r_evt->sources[src_id];
             if (refcount_read(sid) == 0) {
                 ret = REVT_NOTIFY_ENABLE(r_evt, r_evt->evt->id,
                              src_id);
                 if (!ret)
                     refcount_set(sid, 1);
             } else {
                 refcount_inc(sid);
             }
             retvals += !ret;
         }
     } else {
         for (; num_sources; src_id++, num_sources--) {
             sid = &r_evt->sources[src_id];
             if (refcount_dec_and_test(sid))
                 REVT_NOTIFY_DISABLE(r_evt,
                             r_evt->evt->id, src_id);
         }
         retvals = 1;
     }
     mutex_unlock(&r_evt->sources_mtx);
 
     return retvals ? 0 : -EINVAL;
 }
 
 static int scmi_enable_events(struct scmi_event_handler *hndl)
 {
     int ret = 0;
 
     if (!hndl->enabled) {
         ret = __scmi_enable_evt(hndl->r_evt,
                     KEY_XTRACT_SRC_ID(hndl->key), true);
         if (!ret)
             hndl->enabled = true;
     }
 
     return ret;
 }
 
 static int scmi_disable_events(struct scmi_event_handler *hndl)
 {
     int ret = 0;
 
     if (hndl->enabled) {
         ret = __scmi_enable_evt(hndl->r_evt,
                     KEY_XTRACT_SRC_ID(hndl->key), false);
         if (!ret)
             hndl->enabled = false;
     }
 
     return ret;
 }
 
 /**
  * scmi_put_handler_unlocked()  - Put an event handler
  * @ni: A reference to the notification instance to use
  * @hndl: The event handler to act upon
  *
  * After having got exclusive access to the registered handlers hashtable,
  * update the refcount and if @hndl is no more in use by anyone:
  * * ask for events' generation disabling
  * * 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 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) {
         protocol_id = r_evt->proto->id;
         mutex_lock(&r_evt->proto->registered_mtx);
     }
 
     freed = scmi_put_handler_unlocked(ni, hndl);
 
     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_protocol_release(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);
     freed = scmi_put_handler_unlocked(ni, hndl);
     mutex_unlock(&r_evt->proto->registered_mtx);
     if (freed)
         scmi_protocol_release(ni->handle, protocol_id);
 }
 
 /**
  * scmi_event_handler_enable_events()  - Enable events associated to an handler
  * @hndl: The Event handler to act upon
  *
  * Return: 0 on Success
  */
 static int scmi_event_handler_enable_events(struct scmi_event_handler *hndl)
 {
     if (scmi_enable_events(hndl)) {
         pr_err("Failed to ENABLE events for key:%X !\n", hndl->key);
         return -EINVAL;
     }
 
     return 0;
 }
 
 /**
  * scmi_notifier_register()  - Register a notifier_block for an event
  * @handle: The handle identifying the platform instance against which the
  *      callback is registered
  * @proto_id: Protocol ID
  * @evt_id: Event ID
  * @src_id: Source ID, when NULL register for events coming form ALL possible
  *      sources
  * @nb: A standard notifier block to register for the specified event
  *
  * Generic helper to register a notifier_block against a protocol event.
  *
  * A notifier_block @nb will be registered for each distinct event identified
  * by the tuple (proto_id, evt_id, src_id) on a dedicated notification chain
  * so that:
  *
  *  (proto_X, evt_Y, src_Z) --> chain_X_Y_Z
  *
  * @src_id meaning is protocol specific and identifies the origin of the event
  * (like domain_id, sensor_id and so forth).
  *
  * @src_id can be NULL to signify that the caller is interested in receiving
  * notifications from ALL the available sources for that protocol OR simply that
  * the protocol does not support distinct sources.
  *
  * As soon as one user for the specified tuple appears, an handler is created,
  * and that specific event's generation is enabled at the platform level, unless
  * an associated registered event is found missing, meaning that the needed
  * protocol is still to be initialized and the handler has just been registered
  * as still pending.
  *
  * Return: 0 on Success
  */
 static int scmi_notifier_register(const struct scmi_handle *handle,
                   u8 proto_id, u8 evt_id, const u32 *src_id,
                   struct notifier_block *nb)
 {
     int ret = 0;
     u32 evt_key;
     struct scmi_event_handler *hndl;
     struct scmi_notify_instance *ni;
 
     ni = scmi_notification_instance_data_get(handle);
     if (!ni)
         return -ENODEV;
 
     evt_key = MAKE_HASH_KEY(proto_id, evt_id,
                 src_id ? *src_id : SRC_ID_MASK);
     hndl = scmi_get_or_create_handler(ni, evt_key);
     if (!hndl)
         return -EINVAL;
 
     blocking_notifier_chain_register(&hndl->chain, nb);
 
     /* Enable events for not pending handlers */
     if (!IS_HNDL_PENDING(hndl)) {
         ret = scmi_event_handler_enable_events(hndl);
         if (ret)
             scmi_put_handler(ni, hndl);
     }
 
     return ret;
 }
 
 /**
  * scmi_notifier_unregister()  - Unregister a notifier_block for an event
  * @handle: The handle identifying the platform instance against which the
  *      callback is unregistered
  * @proto_id: Protocol ID
  * @evt_id: Event ID
  * @src_id: Source ID
  * @nb: The notifier_block to unregister
  *
  * Takes care to unregister the provided @nb from the notification chain
  * associated to the specified event and, if there are no more users for the
  * event handler, frees also the associated event handler structures.
  * (this could possibly cause disabling of event's generation at platform level)
  *
  * Return: 0 on Success
  */
 static int scmi_notifier_unregister(const struct scmi_handle *handle,
                     u8 proto_id, u8 evt_id, const u32 *src_id,
                     struct notifier_block *nb)
 {
     u32 evt_key;
     struct scmi_event_handler *hndl;
     struct scmi_notify_instance *ni;
 
     ni = scmi_notification_instance_data_get(handle);
     if (!ni)
         return -ENODEV;
 
     evt_key = MAKE_HASH_KEY(proto_id, evt_id,
                 src_id ? *src_id : SRC_ID_MASK);
     hndl = scmi_get_handler(ni, evt_key);
     if (!hndl)
         return -EINVAL;
 
     /*
      * Note that this chain unregistration call is safe on its own
      * being internally protected by an rwsem.
      */
     blocking_notifier_chain_unregister(&hndl->chain, nb);
     scmi_put_handler(ni, hndl);
 
     /*
      * This balances the initial get issued in @scmi_notifier_register.
      * If this notifier_block happened to be the last known user callback
      * for this event, the handler is here freed and the event's generation
      * stopped.
      *
      * Note that, an ongoing concurrent lookup on the delivery workqueue
      * path could still hold the refcount to 1 even after this routine
      * completes: in such a case it will be the final put on the delivery
      * path which will finally free this unused handler.
      */
     scmi_put_handler(ni, hndl);
 
     return 0;
 }
 
 struct scmi_notifier_devres {
     const struct scmi_handle *handle;
     u8 proto_id;
     u8 evt_id;
     u32 __src_id;
     u32 *src_id;
     struct notifier_block *nb;
 };
 
 static void scmi_devm_release_notifier(struct device *dev, void *res)
 {
     struct scmi_notifier_devres *dres = res;
 
     scmi_notifier_unregister(dres->handle, dres->proto_id, dres->evt_id,
                  dres->src_id, dres->nb);
 }
 
 /**
  * scmi_devm_notifier_register()  - Managed registration of a notifier_block
  * for an event
  * @sdev: A reference to an scmi_device whose embedded struct device is to
  *    be used for devres accounting.
  * @proto_id: Protocol ID
  * @evt_id: Event ID
  * @src_id: Source ID, when NULL register for events coming form ALL possible
  *      sources
  * @nb: A standard notifier block to register for the specified event
  *
  * Generic devres managed helper to register a notifier_block against a
  * protocol event.
  *
  * Return: 0 on Success
  */
 static int scmi_devm_notifier_register(struct scmi_device *sdev,
                        u8 proto_id, u8 evt_id,
                        const u32 *src_id,
                        struct notifier_block *nb)
 {
     int ret;
     struct scmi_notifier_devres *dres;
 
     dres = devres_alloc(scmi_devm_release_notifier,
                 sizeof(*dres), GFP_KERNEL);
     if (!dres)
         return -ENOMEM;
 
     ret = scmi_notifier_register(sdev->handle, proto_id,
                      evt_id, src_id, nb);
     if (ret) {
         devres_free(dres);
         return ret;
     }
 
     dres->handle = sdev->handle;
     dres->proto_id = proto_id;
     dres->evt_id = evt_id;
     dres->nb = nb;
     if (src_id) {
         dres->__src_id = *src_id;
         dres->src_id = &dres->__src_id;
     } else {
         dres->src_id = NULL;
     }
     devres_add(&sdev->dev, dres);
 
     return ret;
 }
 
 static int scmi_devm_notifier_match(struct device *dev, void *res, void *data)
 {
     struct scmi_notifier_devres *dres = res;
     struct scmi_notifier_devres *xres = data;
 
     if (WARN_ON(!dres || !xres))
         return 0;
 
     return dres->proto_id == xres->proto_id &&
         dres->evt_id == xres->evt_id &&
         dres->nb == xres->nb &&
         ((!dres->src_id && !xres->src_id) ||
           (dres->src_id && xres->src_id &&
            dres->__src_id == xres->__src_id));
 }
 
 /**
  * scmi_devm_notifier_unregister()  - Managed un-registration of a
  * notifier_block for an event
  * @sdev: A reference to an scmi_device whose embedded struct device is to
  *    be used for devres accounting.
  * @proto_id: Protocol ID
  * @evt_id: Event ID
  * @src_id: Source ID, when NULL register for events coming form ALL possible
  *      sources
  * @nb: A standard notifier block to register for the specified event
  *
  * Generic devres managed helper to explicitly un-register a notifier_block
  * against a protocol event, which was previously registered using the above
  * @scmi_devm_notifier_register.
  *
  * Return: 0 on Success
  */
 static int scmi_devm_notifier_unregister(struct scmi_device *sdev,
                      u8 proto_id, u8 evt_id,
                      const u32 *src_id,
                      struct notifier_block *nb)
 {
     int ret;
     struct scmi_notifier_devres dres;
 
     dres.handle = sdev->handle;
     dres.proto_id = proto_id;
     dres.evt_id = evt_id;
     if (src_id) {
         dres.__src_id = *src_id;
         dres.src_id = &dres.__src_id;
     } else {
         dres.src_id = NULL;
     }
 
     ret = devres_release(&sdev->dev, scmi_devm_release_notifier,
                  scmi_devm_notifier_match, &dres);
 
     WARN_ON(ret);
 
     return ret;
 }
 
 /**
  * scmi_protocols_late_init()  - Worker for late initialization
  * @work: The work item to use associated to the proper SCMI instance
  *
  * This kicks in whenever a new protocol has completed its own registration via
  * scmi_register_protocol_events(): it is in charge of scanning the table of
  * pending handlers (registered by users while the related protocol was still
  * not initialized) and finalizing their initialization whenever possible;
  * invalid pending handlers are purged at this point in time.
  */
 static void scmi_protocols_late_init(struct work_struct *work)
 {
     int bkt;
     struct scmi_event_handler *hndl;
     struct scmi_notify_instance *ni;
     struct hlist_node *tmp;
 
     ni = container_of(work, struct scmi_notify_instance, init_work);
 
     /* Ensure protocols and events are up to date */
     smp_rmb();
 
     mutex_lock(&ni->pending_mtx);
     hash_for_each_safe(ni->pending_events_handlers, bkt, tmp, hndl, hash) {
         int ret;
 
         ret = scmi_bind_event_handler(ni, hndl);
         if (!ret) {
             dev_dbg(ni->handle->dev,
                 "finalized PENDING handler - key:%X\n",
                 hndl->key);
             ret = scmi_event_handler_enable_events(hndl);
             if (ret) {
                 dev_dbg(ni->handle->dev,
                     "purging INVALID handler - key:%X\n",
                     hndl->key);
                 scmi_put_active_handler(ni, hndl);
             }
         } else {
             ret = scmi_valid_pending_handler(ni, hndl);
             if (ret) {
                 dev_dbg(ni->handle->dev,
                     "purging PENDING handler - key:%X\n",
                     hndl->key);
                 /* this hndl can be only a pending one */
                 scmi_put_handler_unlocked(ni, hndl);
             }
         }
     }
     mutex_unlock(&ni->pending_mtx);
 }
 
 /*
  * notify_ops are attached to the handle so that can be accessed
  * directly from an scmi_driver to register its own notifiers.
  */
 static const struct scmi_notify_ops notify_ops = {
     .devm_event_notifier_register = scmi_devm_notifier_register,
     .devm_event_notifier_unregister = scmi_devm_notifier_unregister,
     .event_notifier_register = scmi_notifier_register,
     .event_notifier_unregister = scmi_notifier_unregister,
 };
 
 /**
  * scmi_notification_init()  - Initializes Notification Core Support
  * @handle: The handle identifying the platform instance to initialize
  *
  * This function lays out all the basic resources needed by the notification
  * core instance identified by the provided handle: once done, all of the
  * SCMI Protocols can register their events with the core during their own
  * initializations.
  *
  * Note that failing to initialize the core notifications support does not
  * cause the whole SCMI Protocols stack to fail its initialization.
  *
  * SCMI Notification Initialization happens in 2 steps:
  * * initialization: basic common allocations (this function)
  * * registration: protocols asynchronously come into life and registers their
  *         own supported list of events with the core; this causes
  *         further per-protocol allocations
  *
  * Any user's callback registration attempt, referring a still not registered
  * event, will be registered as pending and finalized later (if possible)
  * by scmi_protocols_late_init() work.
  * This allows for lazy initialization of SCMI Protocols due to late (or
  * missing) SCMI drivers' modules loading.
  *
  * Return: 0 on Success
  */
 int scmi_notification_init(struct scmi_handle *handle)
 {
     void *gid;
     struct scmi_notify_instance *ni;
 
     gid = devres_open_group(handle->dev, NULL, GFP_KERNEL);
     if (!gid)
         return -ENOMEM;
 
     ni = devm_kzalloc(handle->dev, sizeof(*ni), GFP_KERNEL);
     if (!ni)
         goto err;
 
     ni->gid = gid;
     ni->handle = handle;
 
     ni->registered_protocols = devm_kcalloc(handle->dev, SCMI_MAX_PROTO,
                         sizeof(char *), GFP_KERNEL);
     if (!ni->registered_protocols)
         goto err;
 
     ni->notify_wq = alloc_workqueue(dev_name(handle->dev),
                     WQ_UNBOUND | WQ_FREEZABLE | WQ_SYSFS,
                     0);
     if (!ni->notify_wq)
         goto err;
 
     mutex_init(&ni->pending_mtx);
     hash_init(ni->pending_events_handlers);
 
     INIT_WORK(&ni->init_work, scmi_protocols_late_init);
 
     scmi_notification_instance_data_set(handle, ni);
     handle->notify_ops = &notify_ops;
     /* Ensure handle is up to date */
     smp_wmb();
 
     dev_info(handle->dev, "Core Enabled.\n");
 
     devres_close_group(handle->dev, ni->gid);
 
     return 0;
 
 err:
     dev_warn(handle->dev, "Initialization Failed.\n");
     devres_release_group(handle->dev, gid);
     return -ENOMEM;
 }
 
 /**
  * scmi_notification_exit()  - Shutdown and clean Notification core
  * @handle: The handle identifying the platform instance to shutdown
  */
 void scmi_notification_exit(struct scmi_handle *handle)
 {
     struct scmi_notify_instance *ni;
 
     ni = scmi_notification_instance_data_get(handle);
     if (!ni)
         return;
     scmi_notification_instance_data_set(handle, NULL);
 
     /* Destroy while letting pending work complete */
     destroy_workqueue(ni->notify_wq);
 
     devres_release_group(ni->handle->dev, ni->gid);
 }

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