[PATCH v13 14/25] firmware: arm_scmi: Add Telemetry generation counter event

[Cristian Marussi]

Add a per-instance generation counter to track configuration changes which
uses the common telemetry events framework.

Signed-off-by: Cristian Marussi <cristian.marussi at arm.com>
---
v11 -->v12
 - reviewed generation counter update logic
v6 --> v7
 - use new Generic event mechanism based on EventFD instead of WaitQ
v5 --> v6
 - add relese semantic to the atomic set of the generation counter
 - use new eventfd_ctx common event logic
---
 drivers/firmware/arm_scmi/telemetry.c | 49 +++++++++++++++++++++++++++
 include/linux/scmi_protocol.h         |  6 ++--
 2 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/arm_scmi/telemetry.c b/drivers/firmware/arm_scmi/telemetry.c
index 31cd63dee3a5..8ce6af2d01c7 100644
--- a/drivers/firmware/arm_scmi/telemetry.c
+++ b/drivers/firmware/arm_scmi/telemetry.c
@@ -16,6 +16,7 @@
 #include <linux/hash.h>
 #include <linux/io.h>
 #include <linux/limits.h>
+#include <linux/lockdep.h>
 #include <linux/minmax.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
@@ -26,6 +27,7 @@
 #include <linux/string.h>
 #include <linux/uuid.h>
 #include <linux/xarray.h>
+#include <linux/wait.h>
 
 #include "protocols.h"
 #include "notify.h"
@@ -35,6 +37,7 @@
 /* Updated only after ALL the mandatory features for that version are merged */
 #define SCMI_PROTOCOL_SUPPORTED_VERSION		0x10000
 
+#define SCMI_TLM_GENERATION_ONE		(SCMI_TLM_GENERATION_INVALID + 1U)
 #define SCMI_TLM_TDCF_MAX_RETRIES	5
 
 #define SCMI_TLM_DE_IMPL_NUM_DWORDS	4
@@ -729,6 +732,37 @@ scmi_telemetry_tde_cache_lookup(struct telemetry_de *tde,
 	return 0;
 }
 
+static inline void __scmi_telemetry_generation_set(struct telemetry_info *ti,
+						   unsigned int new)
+{
+	int ret;
+
+	atomic_set_release(&ti->info.generation, new);
+
+	ret = scmi_telemetry_event_signal(ti, SCMI_TLM_EVT_GENERATION);
+	if (ret)
+		dev_warn_once(ti->ph->dev,
+			      "Could NOT signal telemetry event %d\n",
+			      SCMI_TLM_EVT_GENERATION);
+}
+
+static inline void scmi_telemetry_generation_update(struct telemetry_info *ti)
+{
+	unsigned int next;
+
+	lockdep_assert_held(&ti->config_mtx);
+
+	/* Wrap around skipping invalid generation 0 */
+	next = (atomic_read(&ti->info.generation) + 1) ?: SCMI_TLM_GENERATION_ONE;
+
+	__scmi_telemetry_generation_set(ti, next);
+}
+
+static inline void scmi_telemetry_generation_reset(struct telemetry_info *ti)
+{
+	__scmi_telemetry_generation_set(ti, SCMI_TLM_GENERATION_ONE);
+}
+
 struct scmi_tlm_de_priv {
 	struct telemetry_info *ti;
 	void *next;
@@ -2849,6 +2883,9 @@ scmi_telemetry_remote_state_update_needed(struct telemetry_info *ti,
 						  is_group ? obj : NULL,
 						  !is_group ? obj : NULL);
 
+		/* A local change can have an impact anyway */
+		scmi_telemetry_generation_update(ti);
+
 		return false;
 	}
 
@@ -2941,6 +2978,8 @@ static int scmi_telemetry_tde_state_set(const struct scmi_protocol_handle *ph,
 			scmi_telemetry_state_cache_update(ti, enable, &de->enabled,
 							  tstamp, &de->tstamp_enabled,
 							  NULL, de);
+
+			scmi_telemetry_generation_update(ti);
 		}
 	}
 
@@ -2985,6 +3024,8 @@ static int scmi_telemetry_group_state_set(const struct scmi_protocol_handle *ph,
 			scmi_telemetry_state_cache_update(ti, enable, &grp->enabled,
 							  tstamp, &grp->tstamp_enabled,
 							  grp, NULL);
+
+			scmi_telemetry_generation_update(ti);
 		}
 	}
 
@@ -3136,6 +3177,9 @@ scmi_telemetry_collection_configure(const struct scmi_protocol_handle *ph,
 
 	ph->xops->xfer_put(ph, t);
 
+	if (!ret)
+		scmi_telemetry_generation_update(ti);
+
 	return ret;
 }
 
@@ -3672,6 +3716,9 @@ static int scmi_telemetry_reset(const struct scmi_protocol_handle *ph)
 	ret = ph->xops->do_xfer(ph, t);
 	if (!ret) {
 		scmi_telemetry_local_resources_reset(ti);
+		/* Reset generation now that server has been reset */
+		scmi_telemetry_generation_reset(ti);
+
 		/* NO need to lookup the initial state we have just reset all */
 	}
 
@@ -4244,6 +4291,8 @@ static int scmi_telemetry_instance_init(struct telemetry_info *ti)
 		INIT_LIST_HEAD(&ti->events[i]);
 	mutex_init(&ti->events_mtx);
 
+	/* Generation counter init */
+	atomic_set(&ti->info.generation, SCMI_TLM_GENERATION_ONE);
 	atomic_set(&ti->des_enabled[ENA_STATE], 0);
 	atomic_set(&ti->des_enabled[ENA_TSTAMP], 0);
 	mutex_init(&ti->des_enabled_mtx);
diff --git a/include/linux/scmi_protocol.h b/include/linux/scmi_protocol.h
index 8ca6803df60a..0210247c0166 100644
--- a/include/linux/scmi_protocol.h
+++ b/include/linux/scmi_protocol.h
@@ -891,6 +891,7 @@ enum scmi_telemetry_collection {
 	SCMI_TLM_SINGLE_READ,
 };
 
+#define SCMI_TLM_GENERATION_INVALID	0U
 #define SCMI_TLM_GRP_INVALID		0xFFFFFFFF
 
 struct scmi_telemetry_intervals {
@@ -986,6 +987,7 @@ struct scmi_telemetry_info {
 	bool enabled;
 	bool notif_enabled;
 	enum scmi_telemetry_collection current_mode;
+	atomic_t generation;
 };
 
 struct scmi_telemetry_de_sample {
@@ -996,7 +998,7 @@ struct scmi_telemetry_de_sample {
 };
 
 enum scmi_telemetry_event {
-	SCMI_TLM_EVT_DUMMY,
+	SCMI_TLM_EVT_GENERATION,
 	SCMI_TLM_EVT_MAX,
 };
 
@@ -1022,11 +1024,11 @@ enum scmi_telemetry_event {
  *		    the ones belonging to a specific group when provided.
  *		    This causes an immediate update platform-side of all the
  *		    enabled DEs.
- * @reset: reset configuration and telemetry data.
  * @event_subscribe: subscribe to the specified event @type using the provided
  *		     @eventfd_ctx.
  * @event_unsubscribe: unsubscribe to the specified event @type the previously
  *		       registered @eventfd_ctx.
+ * @reset: reset configuration and telemetry data.
  */
 struct scmi_telemetry_proto_ops {
 	const struct scmi_telemetry_info __must_check *(*info_get)
-- 
2.54.0