* [PATCH 1/2] firmware: qcom: scm: add trace events for the SMC call interface
2026-05-06 10:37 [PATCH 0/2] firmware: qcom: scm: add tracepoints for the SMC call interface Yuvaraj Ranganathan
@ 2026-05-06 10:37 ` Yuvaraj Ranganathan
2026-05-21 12:03 ` Konrad Dybcio
2026-05-06 10:37 ` [PATCH 2/2] firmware: qcom: scm: instrument SMC call path with tracepoints Yuvaraj Ranganathan
1 sibling, 1 reply; 5+ messages in thread
From: Yuvaraj Ranganathan @ 2026-05-06 10:37 UTC (permalink / raw)
To: Bjorn Andersson, Konrad Dybcio
Cc: kernel, linux-kernel, linux-arm-msm, Yuvaraj Ranganathan
The SCM SMC call path is opaque at runtime. Stalls caused by firmware
congestion, QCOM_SCM_WAITQ_SLEEP/RESUME cycles, and EBUSY retry loops
are invisible without recompiling the kernel with temporary printk
statements or attaching a hardware debugger.
Add five TRACE_EVENTs covering the complete lifecycle of an SCM call:
scm_smc_request
Emit before each arm_smccc_smc_quirk() invocation. Records the
SMC function ID, decoded service and command identifiers, argument
count, and up to six register arguments in hex and decimal. Because
the caller loops on QCOM_SCM_INTERRUPTED, this event fires once per
physical SMC instruction including inte
scm_smc_done
Emit after the outer __scm_smc_do() returns, pairing each
request with its final outcome. Records the SMC function ID, the
kernel error code returned to the caller, and the four firmware
result registers a0-a3.
scm_waitq_sleep
Emit when the firmware returns QCOM_SCM_WAITQ_SLEEP. Records
the wait-queue context and the SMC call context handles required
to issue the matching WAITQ_RESUME.
scm_waitq_resume
Emit just before constructing and sending the WAITQ_RESUME
follow-up call. Records the SMC call context handle being resumed.
scm_waitq_get_wq_ctx
Emit after a successful WAITQ_GET_WQ_CTX fast-call. Records
the returned wait-queue context, flags, and more_pending indicator.
These events let ftrace and perf reconstruct the full sequence of
firmware interactions, measure per-call and end-to-end latency, and
attribute waitqueue stalls to specific service/command pairs without
modifying driver source.
Signed-off-by: Yuvaraj Ranganathan <yuvaraj.ranganathan@oss.qualcomm.com>
---
drivers/firmware/qcom/qcom_scm_trace.h | 143 +++++++++++++++++++++++++++++++++
1 file changed, 143 insertions(+)
diff --git a/drivers/firmware/qcom/qcom_scm_trace.h b/drivers/firmware/qcom/qcom_scm_trace.h
new file mode 100644
index 000000000000..ca8b120563ad
--- /dev/null
+++ b/drivers/firmware/qcom/qcom_scm_trace.h
@@ -0,0 +1,143 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
+ */
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM qcom_scm
+
+#if !defined(_TRACE_SCM_SMC_INTERFACE_H) || defined(TRACE_HEADER_MULTI_READ)
+
+#define _TRACE_SCM_SMC_INTERFACE_H
+
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(scm_smc_request,
+
+ TP_PROTO(unsigned long a0, const struct arm_smccc_args *smc),
+
+ TP_ARGS(a0, smc),
+
+ TP_STRUCT__entry(
+ __field(u64, smc_id)
+ __field(u8, svc_id)
+ __field(u8, cmd_id)
+ __field(u8, args_cnt)
+ __dynamic_array(unsigned long, args,
+ min_t(u8, (smc->args[1] & 0xF), (u8)6))
+ ),
+
+ TP_fast_assign(
+ __entry->smc_id = a0;
+ __entry->svc_id = (smc->args[0] >> 8) & 0xFF;
+ __entry->cmd_id = smc->args[0] & 0xFF;
+ u8 n = min_t(u8, (smc->args[1] & 0xF), (u8)6);
+
+ __entry->args_cnt = n;
+
+ unsigned long *dst = __get_dynamic_array(args);
+
+ for (int i = 0; i < n; i++)
+ dst[i] = smc->args[2 + i];
+ ),
+
+ TP_printk("smc_id:0x%08llx svc_id:0x%02x cmd_id:0x%02x args_cnt:%u args:%s",
+ __entry->smc_id, __entry->svc_id, __entry->cmd_id, __entry->args_cnt,
+ __print_dynamic_array(args, sizeof(unsigned long)))
+);
+
+TRACE_EVENT(scm_waitq_sleep,
+
+ TP_PROTO(u32 wq_ctx, u32 smc_ctx),
+
+ TP_ARGS(wq_ctx, smc_ctx),
+
+ TP_STRUCT__entry(
+ __field(u32, wq_ctx)
+ __field(u32, smc_call_ctx)
+ ),
+
+ TP_fast_assign(
+ __entry->wq_ctx = wq_ctx;
+ __entry->smc_call_ctx = smc_ctx;
+ ),
+
+ TP_printk("wq_ctx:%u, smc_call_ctx:%u", __entry->wq_ctx, __entry->smc_call_ctx)
+);
+
+TRACE_EVENT(scm_waitq_resume,
+
+ TP_PROTO(u32 smc_ctx),
+
+ TP_ARGS(smc_ctx),
+
+ TP_STRUCT__entry(
+ __field(u32, smc_call_ctx)
+ ),
+
+ TP_fast_assign(
+ __entry->smc_call_ctx = smc_ctx;
+ ),
+
+ TP_printk("smc_call_ctx:%u", __entry->smc_call_ctx)
+);
+
+TRACE_EVENT(scm_waitq_get_wq_ctx,
+
+ TP_PROTO(u32 wq_ctx, u32 flags, u32 pending),
+
+ TP_ARGS(wq_ctx, flags, pending),
+
+ TP_STRUCT__entry(
+ __field(u32, wq_ctx)
+ __field(u32, flags)
+ __field(u32, more_pending)
+ ),
+
+ TP_fast_assign(
+ __entry->wq_ctx = wq_ctx;
+ __entry->flags = flags;
+ __entry->more_pending = pending;
+ ),
+
+ TP_printk("wq_ctx:%u, flags:%u, more_pending:%u",
+ __entry->wq_ctx, __entry->flags, __entry->more_pending)
+);
+
+TRACE_EVENT(scm_smc_done,
+
+ TP_PROTO(int ret, u64 smc_id, struct arm_smccc_res *smc_res),
+
+ TP_ARGS(ret, smc_id, smc_res),
+
+ TP_STRUCT__entry(
+ __field(int, ret)
+ __field(u64, smc_id)
+ __field(unsigned long, res)
+ __field(unsigned long, res0)
+ __field(unsigned long, res1)
+ __field(unsigned long, res2)
+ ),
+
+ TP_fast_assign(
+ __entry->ret = ret;
+ __entry->smc_id = smc_id;
+ __entry->res = smc_res->a0;
+ __entry->res0 = smc_res->a1;
+ __entry->res1 = smc_res->a2;
+ __entry->res2 = smc_res->a3;
+ ),
+
+ TP_printk("smc_id:0x%08llx, ret:%d res_to_callee:0x%lx res0:0x%lx res1:0x%lx res2:0x%lx",
+ __entry->smc_id, __entry->ret, __entry->res,
+ __entry->res0, __entry->res1, __entry->res2)
+);
+
+#endif /* _TRACE_SCM_SMC_INTERFACE_H */
+
+#undef TRACE_INCLUDE_PATH
+#define TRACE_INCLUDE_PATH .
+#define TRACE_INCLUDE_FILE qcom_scm_trace
+
+#include <trace/define_trace.h>
+
--
2.34.1
^ permalink raw reply [flat|nested] 5+ messages in thread* [PATCH 2/2] firmware: qcom: scm: instrument SMC call path with tracepoints
2026-05-06 10:37 [PATCH 0/2] firmware: qcom: scm: add tracepoints for the SMC call interface Yuvaraj Ranganathan
2026-05-06 10:37 ` [PATCH 1/2] firmware: qcom: scm: add trace events " Yuvaraj Ranganathan
@ 2026-05-06 10:37 ` Yuvaraj Ranganathan
2026-05-21 12:03 ` Konrad Dybcio
1 sibling, 1 reply; 5+ messages in thread
From: Yuvaraj Ranganathan @ 2026-05-06 10:37 UTC (permalink / raw)
To: Bjorn Andersson, Konrad Dybcio
Cc: kernel, linux-kernel, linux-arm-msm, Yuvaraj Ranganathan
Wire the five tracepoints defined in qcom_scm_trace.h into the SMC
execution path by including the header with CREATE_TRACE_POINTS.
Signed-off-by: Yuvaraj Ranganathan <yuvaraj.ranganathan@oss.qualcomm.com>
---
drivers/firmware/qcom/Makefile | 1 +
drivers/firmware/qcom/qcom_scm-smc.c | 10 ++++++++++
2 files changed, 11 insertions(+)
diff --git a/drivers/firmware/qcom/Makefile b/drivers/firmware/qcom/Makefile
index 0be40a1abc13..b679d3fc2c26 100644
--- a/drivers/firmware/qcom/Makefile
+++ b/drivers/firmware/qcom/Makefile
@@ -5,6 +5,7 @@
obj-$(CONFIG_QCOM_SCM) += qcom-scm.o
qcom-scm-objs += qcom_scm.o qcom_scm-smc.o qcom_scm-legacy.o
+CFLAGS_qcom_scm-smc.o := -I$(src)
obj-$(CONFIG_QCOM_TZMEM) += qcom_tzmem.o
obj-$(CONFIG_QCOM_QSEECOM) += qcom_qseecom.o
obj-$(CONFIG_QCOM_QSEECOM_UEFISECAPP) += qcom_qseecom_uefisecapp.o
diff --git a/drivers/firmware/qcom/qcom_scm-smc.c b/drivers/firmware/qcom/qcom_scm-smc.c
index 574930729ddd..01999c22659c 100644
--- a/drivers/firmware/qcom/qcom_scm-smc.c
+++ b/drivers/firmware/qcom/qcom_scm-smc.c
@@ -24,6 +24,9 @@ struct arm_smccc_args {
unsigned long args[8];
};
+#define CREATE_TRACE_POINTS
+#include "qcom_scm_trace.h"
+
static DEFINE_MUTEX(qcom_scm_lock);
#define QCOM_SCM_EBUSY_WAIT_MS 30
@@ -44,6 +47,7 @@ static void __scm_smc_do_quirk(const struct arm_smccc_args *smc,
quirk.state.a6 = 0;
do {
+ trace_scm_smc_request(a0, smc);
arm_smccc_smc_quirk(a0, smc->args[1], smc->args[2],
smc->args[3], smc->args[4], smc->args[5],
quirk.state.a6, smc->args[7], res, &quirk);
@@ -83,6 +87,7 @@ int scm_get_wq_ctx(u32 *wq_ctx, u32 *flags, u32 *more_pending)
if (ret)
return ret;
+ trace_scm_waitq_get_wq_ctx(get_wq_res.a1, get_wq_res.a2, get_wq_res.a3);
*wq_ctx = get_wq_res.a1;
*flags = get_wq_res.a2;
*more_pending = get_wq_res.a3;
@@ -105,10 +110,12 @@ static int __scm_smc_do_quirk_handle_waitq(struct device *dev, struct arm_smccc_
wq_ctx = res->a1;
smc_call_ctx = res->a2;
+ trace_scm_waitq_sleep(wq_ctx, smc_call_ctx);
ret = qcom_scm_wait_for_wq_completion(wq_ctx);
if (ret)
return ret;
+ trace_scm_waitq_resume(smc_call_ctx);
fill_wq_resume_args(&resume, smc_call_ctx);
smc = &resume;
}
@@ -201,6 +208,9 @@ int __scm_smc_call(struct device *dev, const struct qcom_scm_desc *desc,
}
ret = __scm_smc_do(dev, &smc, &smc_res, atomic);
+
+ trace_scm_smc_done(ret, smc.args[0], &smc_res);
+
if (ret)
return ret;
--
2.34.1
^ permalink raw reply [flat|nested] 5+ messages in thread