[PATCH v2 1/2] firmware: qcom: scm: add trace events for the SMC call interface

[Yuvaraj Ranganathan <yuvaraj.ranganathan@oss.qualcomm.com>]

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.

Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
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..6c911124fc56
--- /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