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Subject[PATCH v2 2/2] drivers: firmware: scmi: Extend SCMI transport layer by trace events
Date
From: Lukasz Luba <lukasz.luba@arm.com>

The SCMI transport layer communicates via mailboxes and shared memory with
firmware running on a microcontroller. It is platform specific how long it
takes to pass a SCMI message. The most sensitive requests are coming from
CPUFreq subsystem, which might be used by the scheduler.
Thus, there is a need to measure these delays and capture anomalies.
This change introduces trace events wrapped around transfer code.

According to Jim's suggestion a unique transfer_id is to distinguish
similar entries which might have the same message id, protocol id and
sequence. This is a case then there are some timeouts in transfers.

Suggested-by: Jim Quinlan <james.quinlan@broadcom.com>
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
---
drivers/firmware/arm_scmi/common.h | 2 ++
drivers/firmware/arm_scmi/driver.c | 18 ++++++++++++++++++
2 files changed, 20 insertions(+)

diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
index 5237c2ff79fe..df35358ff324 100644
--- a/drivers/firmware/arm_scmi/common.h
+++ b/drivers/firmware/arm_scmi/common.h
@@ -81,6 +81,7 @@ struct scmi_msg {
/**
* struct scmi_xfer - Structure representing a message flow
*
+ * @transfer_id: Unique ID for debug & profiling purpose
* @hdr: Transmit message header
* @tx: Transmit message
* @rx: Receive message, the buffer should be pre-allocated to store
@@ -90,6 +91,7 @@ struct scmi_msg {
* @async: pointer to delayed response message received event completion
*/
struct scmi_xfer {
+ int transfer_id;
struct scmi_msg_hdr hdr;
struct scmi_msg tx;
struct scmi_msg rx;
diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 3eb0382491ce..15c5629ad2cd 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -29,6 +29,9 @@

#include "common.h"

+#define CREATE_TRACE_POINTS
+#include <trace/events/scmi.h>
+
#define MSG_ID_MASK GENMASK(7, 0)
#define MSG_XTRACT_ID(hdr) FIELD_GET(MSG_ID_MASK, (hdr))
#define MSG_TYPE_MASK GENMASK(9, 8)
@@ -61,6 +64,8 @@ enum scmi_error_codes {
static LIST_HEAD(scmi_list);
/* Protection for the entire list */
static DEFINE_MUTEX(scmi_list_mutex);
+/* Track the unique id for the transfers for debug & profiling purpose */
+static atomic_t transfer_last_id;

/**
* struct scmi_xfers_info - Structure to manage transfer information
@@ -304,6 +309,7 @@ static struct scmi_xfer *scmi_xfer_get(const struct scmi_handle *handle,
xfer = &minfo->xfer_block[xfer_id];
xfer->hdr.seq = xfer_id;
reinit_completion(&xfer->done);
+ xfer->transfer_id = atomic_inc_return(&transfer_last_id);

return xfer;
}
@@ -374,6 +380,10 @@ static void scmi_rx_callback(struct mbox_client *cl, void *m)

scmi_fetch_response(xfer, mem);

+ trace_scmi_rx_done(xfer->transfer_id, xfer->hdr.id,
+ xfer->hdr.protocol_id, xfer->hdr.seq,
+ msg_type);
+
if (msg_type == MSG_TYPE_DELAYED_RESP)
complete(xfer->async_done);
else
@@ -439,6 +449,10 @@ int scmi_do_xfer(const struct scmi_handle *handle, struct scmi_xfer *xfer)
if (unlikely(!cinfo))
return -EINVAL;

+ trace_scmi_xfer_begin(xfer->transfer_id, xfer->hdr.id,
+ xfer->hdr.protocol_id, xfer->hdr.seq,
+ xfer->hdr.poll_completion);
+
ret = mbox_send_message(cinfo->chan, xfer);
if (ret < 0) {
dev_dbg(dev, "mbox send fail %d\n", ret);
@@ -478,6 +492,10 @@ int scmi_do_xfer(const struct scmi_handle *handle, struct scmi_xfer *xfer)
*/
mbox_client_txdone(cinfo->chan, ret);

+ trace_scmi_xfer_end(xfer->transfer_id, xfer->hdr.id,
+ xfer->hdr.protocol_id, xfer->hdr.seq,
+ xfer->hdr.status);
+
return ret;
}

--
2.17.1
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