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>
Link: https://lore.kernel.org/r/20260522-scm-tracepoints-v2-1-e27cdbe0c585@oss.qualcomm.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
