[PATCH v2 0/3] firmware: arm_scmi: Add xfer inflight debug and trace

[PATCH v2 0/3] firmware: arm_scmi: Add xfer inflight debug and trace

[Philip Radford]

Hi all,

This series adds a new counter to the Arm SCMI firmware driver to track
the number of in-flight message transfers during debug and trace. This
will be useful for examining behaviour under a large load with regards
to concurrent messages being sent and received. As the counter only gives
a live value, printing the value in trace allows logging of the in-flight
xfers.

The series is divided into three small patches:
Patch [1/3]
        - Adds a function to decrement debug counters, similar to the
		  existing counter to increment debug counters.
Patch [2/3]
        - Adds a new xfers_inflight debug counter to track active
		  transfers.
Patch [3/3]
        - Enhances two tracepoints (scmi_xfer_begin and scmi_xfer_end) to
          include the number of in-flight transfers. Also adds a function
		  (scmi_inflight_count) that retrieves the current in-flight count
		  for use in tracing.

This series is based off the branch sudeep/for-next/scmi/updates at commit
397f802d06c4 ("firmware: arm_scmi: quirk: Force perf level get fastchannel").

Regards,
Phil
---
V1->V2
- Amendments to commit messages
- Final commit of V1 squashed into commit three
- Removal of erroneous blank space
- rebased on sudeep/for-next/scmi/updates as previously based on v6.16-rc2


Philip Radford (3):
  firmware: arm_scmi: Add debug decrement counter
  firmware: arm_scmi: Add xfer_inflight counter
  include: trace: Add inflight_xfer counter tracepoint

 drivers/firmware/arm_scmi/common.h   |  8 ++++++++
 drivers/firmware/arm_scmi/driver.c   | 28 ++++++++++++++++++++++++++--
 drivers/firmware/arm_scmi/raw_mode.c |  6 ++++--
 include/trace/events/scmi.h          | 24 ++++++++++++++----------
 4 files changed, 52 insertions(+), 14 deletions(-)

--
2.25.1

[PATCH v2 1/3] firmware: arm_scmi: Add debug decrement counter

[Philip Radford]

Create scmi_dec_count function to decrease any of the Arm SCMI
debug counters. There is already an scmi_inc_count function
but no decrement function.

Reviewed-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Philip Radford <philip.radford@arm.com>
---
V1->V2
- Amended commit message
---
 drivers/firmware/arm_scmi/common.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
index dab758c5fdea..c6495c4a0e8a 100644
--- a/drivers/firmware/arm_scmi/common.h
+++ b/drivers/firmware/arm_scmi/common.h
@@ -314,6 +314,12 @@ static inline void scmi_inc_count(atomic_t *arr, int stat)
 		atomic_inc(&arr[stat]);
 }
 
+static inline void scmi_dec_count(atomic_t *arr, int stat)
+{
+	if (IS_ENABLED(CONFIG_ARM_SCMI_DEBUG_COUNTERS))
+		atomic_dec(&arr[stat]);
+}
+
 enum scmi_bad_msg {
 	MSG_UNEXPECTED = -1,
 	MSG_INVALID = -2,
-- 
2.25.1

[PATCH v2 2/3] firmware: arm_scmi: Add xfer_inflight counter

[Philip Radford]

Add a counter to the debug_counters struct to record the current
number of outstanding inflight xfers.

Reviewed-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Philip Radford <philip.radford@arm.com>
---
V1->V2
- Amended commit message
---
 drivers/firmware/arm_scmi/common.h |  1 +
 drivers/firmware/arm_scmi/driver.c | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
index c6495c4a0e8a..ad9232c982ce 100644
--- a/drivers/firmware/arm_scmi/common.h
+++ b/drivers/firmware/arm_scmi/common.h
@@ -305,6 +305,7 @@ enum debug_counters {
 	ERR_MSG_INVALID,
 	ERR_MSG_NOMEM,
 	ERR_PROTOCOL,
+	XFERS_INFLIGHT,
 	SCMI_DEBUG_COUNTERS_LAST
 };
 
diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 2699c8efef0a..46f15c5b4998 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -190,6 +190,7 @@ struct scmi_info {
 };
 
 #define handle_to_scmi_info(h)	container_of(h, struct scmi_info, handle)
+#define tx_minfo_to_scmi_info(h) container_of(h, struct scmi_info, tx_minfo)
 #define bus_nb_to_scmi_info(nb)	container_of(nb, struct scmi_info, bus_nb)
 #define req_nb_to_scmi_info(nb)	container_of(nb, struct scmi_info, dev_req_nb)
 
@@ -603,9 +604,14 @@ static inline void
 scmi_xfer_inflight_register_unlocked(struct scmi_xfer *xfer,
 				     struct scmi_xfers_info *minfo)
 {
+	/* In this context minfo will be tx_minfo due to the xfer pending */
+	struct scmi_info *info = tx_minfo_to_scmi_info(minfo);
+
 	/* Set in-flight */
 	set_bit(xfer->hdr.seq, minfo->xfer_alloc_table);
 	hash_add(minfo->pending_xfers, &xfer->node, xfer->hdr.seq);
+	scmi_inc_count(info->dbg->counters, XFERS_INFLIGHT);
+
 	xfer->pending = true;
 }
 
@@ -807,9 +813,13 @@ __scmi_xfer_put(struct scmi_xfers_info *minfo, struct scmi_xfer *xfer)
 	spin_lock_irqsave(&minfo->xfer_lock, flags);
 	if (refcount_dec_and_test(&xfer->users)) {
 		if (xfer->pending) {
+			struct scmi_info *info = tx_minfo_to_scmi_info(minfo);
+
 			scmi_xfer_token_clear(minfo, xfer);
 			hash_del(&xfer->node);
 			xfer->pending = false;
+
+			scmi_dec_count(info->dbg->counters, XFERS_INFLIGHT);
 		}
 		hlist_add_head(&xfer->node, &minfo->free_xfers);
 	}
@@ -2909,6 +2919,7 @@ static const char * const dbg_counter_strs[] = {
 	"err_msg_invalid",
 	"err_msg_nomem",
 	"err_protocol",
+	"xfers_inflight",
 };
 
 static ssize_t reset_all_on_write(struct file *filp, const char __user *buf,
-- 
2.25.1

[PATCH v2 3/3] include: trace: Add inflight_xfer counter tracepoint

[Philip Radford]

Add tracepoint for inflight_xfers and patch all related callsites.

firmware: arm_scmi: Add new inflight tracing functionality

Add scmi_inflight_count function to fetch the current xfer
inflight count to use in trace.

Reviewed-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Philip Radford <philip.radford@arm.com>
---
V1->V2
- Squashed final commit adding functionality into this commit
- Cleaned up erroneous blank space
---
 drivers/firmware/arm_scmi/common.h   |  1 +
 drivers/firmware/arm_scmi/driver.c   | 17 +++++++++++++++--
 drivers/firmware/arm_scmi/raw_mode.c |  6 ++++--
 include/trace/events/scmi.h          | 24 ++++++++++++++----------
 4 files changed, 34 insertions(+), 14 deletions(-)

diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
index ad9232c982ce..07b9e629276d 100644
--- a/drivers/firmware/arm_scmi/common.h
+++ b/drivers/firmware/arm_scmi/common.h
@@ -505,4 +505,5 @@ static struct platform_driver __drv = {					       \
 void scmi_notification_instance_data_set(const struct scmi_handle *handle,
 					 void *priv);
 void *scmi_notification_instance_data_get(const struct scmi_handle *handle);
+int scmi_inflight_count(const struct scmi_handle *handle);
 #endif /* _SCMI_COMMON_H */
diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 46f15c5b4998..ccc70f10408f 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -1440,7 +1440,8 @@ static int do_xfer(const struct scmi_protocol_handle *ph,
 
 	trace_scmi_xfer_begin(xfer->transfer_id, xfer->hdr.id,
 			      xfer->hdr.protocol_id, xfer->hdr.seq,
-			      xfer->hdr.poll_completion);
+			      xfer->hdr.poll_completion,
+			      scmi_inflight_count(&info->handle));
 
 	/* Clear any stale status */
 	xfer->hdr.status = SCMI_SUCCESS;
@@ -1476,7 +1477,8 @@ static int do_xfer(const struct scmi_protocol_handle *ph,
 		info->desc->ops->mark_txdone(cinfo, ret, xfer);
 
 	trace_scmi_xfer_end(xfer->transfer_id, xfer->hdr.id,
-			    xfer->hdr.protocol_id, xfer->hdr.seq, ret);
+			    xfer->hdr.protocol_id, xfer->hdr.seq, ret,
+			    scmi_inflight_count(&info->handle));
 
 	return ret;
 }
@@ -3413,6 +3415,17 @@ static struct dentry *scmi_debugfs_init(void)
 	return d;
 }
 
+int scmi_inflight_count(const struct scmi_handle *handle)
+{
+	if (IS_ENABLED(CONFIG_ARM_SCMI_DEBUG_COUNTERS)) {
+		struct scmi_info *info = handle_to_scmi_info(handle);
+
+		return atomic_read(&info->dbg->counters[XFERS_INFLIGHT]);
+	} else {
+		return 0;
+	}
+}
+
 static int __init scmi_driver_init(void)
 {
 	scmi_quirks_initialize();
diff --git a/drivers/firmware/arm_scmi/raw_mode.c b/drivers/firmware/arm_scmi/raw_mode.c
index 3d543b1d8947..73db5492ab44 100644
--- a/drivers/firmware/arm_scmi/raw_mode.c
+++ b/drivers/firmware/arm_scmi/raw_mode.c
@@ -475,7 +475,8 @@ static void scmi_xfer_raw_worker(struct work_struct *work)
 			raw->desc->ops->mark_txdone(rw->cinfo, ret, xfer);
 
 		trace_scmi_xfer_end(xfer->transfer_id, xfer->hdr.id,
-				    xfer->hdr.protocol_id, xfer->hdr.seq, ret);
+				    xfer->hdr.protocol_id, xfer->hdr.seq,
+				    ret, scmi_inflight_count(raw->handle));
 
 		/* Wait also for an async delayed response if needed */
 		if (!ret && xfer->async_done) {
@@ -642,7 +643,8 @@ static int scmi_do_xfer_raw_start(struct scmi_raw_mode_info *raw,
 
 	trace_scmi_xfer_begin(xfer->transfer_id, xfer->hdr.id,
 			      xfer->hdr.protocol_id, xfer->hdr.seq,
-			      xfer->hdr.poll_completion);
+			      xfer->hdr.poll_completion,
+			      scmi_inflight_count(raw->handle));
 
 	ret = raw->desc->ops->send_message(rw->cinfo, xfer);
 	if (ret) {
diff --git a/include/trace/events/scmi.h b/include/trace/events/scmi.h
index 127300481123..703b7bb68e44 100644
--- a/include/trace/events/scmi.h
+++ b/include/trace/events/scmi.h
@@ -36,8 +36,8 @@ TRACE_EVENT(scmi_fc_call,
 
 TRACE_EVENT(scmi_xfer_begin,
 	TP_PROTO(int transfer_id, u8 msg_id, u8 protocol_id, u16 seq,
-		 bool poll),
-	TP_ARGS(transfer_id, msg_id, protocol_id, seq, poll),
+		 bool poll, int inflight),
+	TP_ARGS(transfer_id, msg_id, protocol_id, seq, poll, inflight),
 
 	TP_STRUCT__entry(
 		__field(int, transfer_id)
@@ -45,6 +45,7 @@ TRACE_EVENT(scmi_xfer_begin,
 		__field(u8, protocol_id)
 		__field(u16, seq)
 		__field(bool, poll)
+		__field(int, inflight)
 	),
 
 	TP_fast_assign(
@@ -53,11 +54,12 @@ TRACE_EVENT(scmi_xfer_begin,
 		__entry->protocol_id = protocol_id;
 		__entry->seq = seq;
 		__entry->poll = poll;
+		__entry->inflight = inflight;
 	),
 
-	TP_printk("pt=%02X msg_id=%02X seq=%04X transfer_id=%X poll=%u",
-		__entry->protocol_id, __entry->msg_id, __entry->seq,
-		__entry->transfer_id, __entry->poll)
+	TP_printk("pt=%02X msg_id=%02X seq=%04X transfer_id=%X poll=%u inflight=%d",
+		  __entry->protocol_id, __entry->msg_id, __entry->seq,
+		  __entry->transfer_id, __entry->poll, __entry->inflight)
 );
 
 TRACE_EVENT(scmi_xfer_response_wait,
@@ -90,8 +92,8 @@ TRACE_EVENT(scmi_xfer_response_wait,
 
 TRACE_EVENT(scmi_xfer_end,
 	TP_PROTO(int transfer_id, u8 msg_id, u8 protocol_id, u16 seq,
-		 int status),
-	TP_ARGS(transfer_id, msg_id, protocol_id, seq, status),
+		 int status, int inflight),
+	TP_ARGS(transfer_id, msg_id, protocol_id, seq, status, inflight),
 
 	TP_STRUCT__entry(
 		__field(int, transfer_id)
@@ -99,6 +101,7 @@ TRACE_EVENT(scmi_xfer_end,
 		__field(u8, protocol_id)
 		__field(u16, seq)
 		__field(int, status)
+		__field(int, inflight)
 	),
 
 	TP_fast_assign(
@@ -107,11 +110,12 @@ TRACE_EVENT(scmi_xfer_end,
 		__entry->protocol_id = protocol_id;
 		__entry->seq = seq;
 		__entry->status = status;
+		__entry->inflight = inflight;
 	),
 
-	TP_printk("pt=%02X msg_id=%02X seq=%04X transfer_id=%X s=%d",
-		__entry->protocol_id, __entry->msg_id, __entry->seq,
-		__entry->transfer_id, __entry->status)
+	TP_printk("pt=%02X msg_id=%02X seq=%04X transfer_id=%X s=%d inflight=%d",
+		  __entry->protocol_id, __entry->msg_id, __entry->seq,
+		  __entry->transfer_id, __entry->status, __entry->inflight)
 );
 
 TRACE_EVENT(scmi_rx_done,
-- 
2.25.1

Re: [PATCH v2 0/3] firmware: arm_scmi: Add xfer inflight debug and trace

[Sudeep Holla]

On Mon, 30 Jun 2025 10:55:40 +0000, Philip Radford wrote:
> This series adds a new counter to the Arm SCMI firmware driver to track
> the number of in-flight message transfers during debug and trace. This
> will be useful for examining behaviour under a large load with regards
> to concurrent messages being sent and received. As the counter only gives
> a live value, printing the value in trace allows logging of the in-flight
> xfers.
> 
> [...]

Applied to sudeep.holla/linux (for-linux-next), thanks!
(with some commit message changes)

[1/3] firmware: arm_scmi: Add debug decrement counter
      https://git.kernel.org/sudeep.holla/c/555e9174ef06
[2/3] firmware: arm_scmi: Add xfer_inflight counter
      https://git.kernel.org/sudeep.holla/c/a9cd861e61ae
[3/3] include: trace: Add inflight_xfer counter tracepoint
      https://git.kernel.org/sudeep.holla/c/f8e656382b4a
--
Regards,
Sudeep