linux-kernel - [PATCH v3 00/10] coresight: ctcu: Enable byte-cntr function for TMC ETR

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Message-Id: <20250624060438.7469-1-jie.gan@oss.qualcomm.com>
Date: Tue, 24 Jun 2025 14:04:28 +0800
From: Jie Gan <jie.gan@....qualcomm.com>
To: Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        James Clark <james.clark@...aro.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Tingwei Zhang <quic_tingweiz@...cinc.com>, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        jie.gan@....qualcomm.com
Subject: [PATCH v3 00/10] coresight: ctcu: Enable byte-cntr function for TMC ETR

The byte-cntr function provided by the CTCU device is used to count the
trace data entering the ETR. An interrupt is tiggered if the data size
exceeds the threshold set in the BYTECNTRVAL register. The interrupt
handler counts the number of triggered interruptions.

Based on this concept, the irq_cnt can be used to determine whether
the etr_buf is full. The ETR device will be disabled when the active
etr_buf is nearly full or a timeout occurs. The nearly full buffer will
be switched to background after synced. A new buffer will be picked from
the etr_buf_list, then restart the ETR device.

The byte-cntr reading functions can access data from the synced and
deactivated buffer, transferring trace data from the etr_buf to userspace
without stopping the ETR device.

The byte-cntr read operation has integrated with the file node tmc_etr, e.g.
/dev/tmc_etr0
/dev/tmc_etr1

There are two scenarios for the tmc_etr file node with byte-cntr function:
1. BYTECNTRVAL register is configured and byte-cntr is enabled -> byte-cntr read
2. BYTECNTRVAL register is reset or byte-cntr is disabled -> original behavior

Shell commands to enable byte-cntr reading for etr0:
echo 0x10000 > /sys/bus/coresight/devices/ctcu0/irq_val
echo 1 > /sys/bus/coresight/devices/tmc_etr0/enable_sink
echo 1 > /sys/bus/coresight/devices/etm0/enable_source
cat /dev/tmc_etr0

Reset the BYTECNTR register for etr0:
echo 0 > /sys/bus/coresight/devices/ctcu0/irq_val

Changes in V3:
1. The previous solution has been deprecated.
2. Add a etr_buf_list to manage allcated etr buffers.
3. Add a logic to switch buffer for ETR.
4. Add read functions to read trace data from synced etr buffer.
Link to V2 - https://lore.kernel.org/all/20250410013330.3609482-1-jie.gan@oss.qualcomm.com/

Changes in V2:
1. Removed the independent file node /dev/byte_cntr.
2. Integrated the byte-cntr's file operations with current ETR file
   node.
3. Optimized the driver code of the CTCU that associated with byte-cntr.
4. Add kernel document for the export API tmc_etr_get_rwp_offset.
5. Optimized the way to read the rwp_offset according to Mike's
   suggestion.
6. Removed the dependency of the dts patch.
Link to V1 - https://lore.kernel.org/all/20250310090407.2069489-1-quic_jiegan@quicinc.com/

Jie Gan (10):
  coresight: core: Refactoring ctcu_get_active_port and make it generic
  coresight: core: add a new API to retrieve the helper device
  dt-bindings: arm: add an interrupt property for Coresight CTCU
  coresight: ctcu: enable byte-cntr for TMC ETR devices
  coresight: tmc: add etr_buf_list to store allocated etr_buf
  coresight: tmc: add create/delete functions for etr_buf_node
  coresight: tmc: add prepare/unprepare functions for byte-cntr
  coresight: tmc: add a switch buffer function for byte-cntr
  coresight: tmc: add read function for byte-cntr
  arm64: dts: qcom: sa8775p: Add interrupts to CTCU device

 .../testing/sysfs-bus-coresight-devices-ctcu  |   5 +
 .../bindings/arm/qcom,coresight-ctcu.yaml     |  17 ++
 arch/arm64/boot/dts/qcom/sa8775p.dtsi         |   5 +
 drivers/hwtracing/coresight/Makefile          |   2 +-
 drivers/hwtracing/coresight/coresight-core.c  |  54 ++++
 .../coresight/coresight-ctcu-byte-cntr.c      | 102 +++++++
 .../hwtracing/coresight/coresight-ctcu-core.c | 113 ++++++--
 drivers/hwtracing/coresight/coresight-ctcu.h  |  52 +++-
 drivers/hwtracing/coresight/coresight-priv.h  |   4 +
 .../hwtracing/coresight/coresight-tmc-core.c  |  70 ++++-
 .../hwtracing/coresight/coresight-tmc-etr.c   | 270 ++++++++++++++++++
 drivers/hwtracing/coresight/coresight-tmc.h   |  29 ++
 12 files changed, 691 insertions(+), 32 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-coresight-devices-ctcu
 create mode 100644 drivers/hwtracing/coresight/coresight-ctcu-byte-cntr.c

-- 
2.34.1