The byte-cntr function provided by the CTCU device is used to count the
trace data entering the ETR. An interrupt is triggered 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,
for example:
/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 1 > /sys/bus/coresight/devices/ctcu0/irq_enabled0
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_enabled0

---
Changes in v16:
1. Remove lock/unlock processes in patch "coresight: tmc: add create/clean
   functions for etr_buf_list" because we are allocating/freeing memory.
- Link to v15: https://lore.kernel.org/r/20260313-enable-byte-cntr-for-ctcu-v15-0-1777f14ed319@oss.qualcomm.com

Changes in v15:
1. add lockdep_assert_held in patch "coresight: tmc: add create/clean
   functions for etr_buf_list"
2. optimize tmc_clean_etr_buf_list function
3. optimize the patch "enable byte-cntr for TMC ETR devices" according
   to Suzuki's comments
   - call byte_cntr_sysfs_ops from etr_sysfs_ops
   - optimize the lock usage in all functions
   - remove the buf_node parameter in etr_drvdata, move it to
     byte_cntr_data
   - move the tmc_reset_sysfs_buf function to tmc-etr.c
   - add a read flag to struct etr_buf_node to allow updating pos while
     traversing etr_buf_list during data reads.
Link to v14: https://lore.kernel.org/r/20260309-enable-byte-cntr-for-ctcu-v14-0-c08823e5a8e6@oss.qualcomm.com

Changes in V14:
1. Drop the patch: integrate byte-cntr's sysfs_ops with tmc sysfs file_ops
2. Replace tmc_sysfs_ops with byte_cntr_sysfs_ops in byte_cntr_start
   function and restore etr_sysfs_ops in byte_cntr_unprepare function.
3. Remove redundant checks in byte‑cntr functions.
Link to V13: https://lore.kernel.org/all/20260223-enable-byte-cntr-for-ctcu-v13-0-9cb44178b250@oss.qualcomm.com/

Changes in v13:
1. initilize the byte_cntr_data->raw_spin_lock before using.
2. replace kzalloc with kzalloc_obj.
Link to V12: https://lore.kernel.org/all/20260203-enable-byte-cntr-for-ctcu-v12-0-7bf81b86b70e@oss.qualcomm.com/

Changes in v12:
1. Add a new function for retrieving the CTCU's coresight_dev instead of
   refactor the existing function.
Link to v11: https://lore.kernel.org/r/20260126-enable-byte-cntr-for-ctcu-v11-0-c0af66ba15cf@oss.qualcomm.com

Changes in v11:
1. Correct the description in patch1 for the function coresight_get_in_port.
2. Renaming the sysfs_ops to tmc_sysfs_ops per Suzuki's suggestion.
Link to v10: https://lore.kernel.org/r/20260122-enable-byte-cntr-for-ctcu-v10-0-22978e3c169f@oss.qualcomm.com

Changes in v10:
1. fix a free memory issue that is reported by robot for patch 2.
Link to v9: https://lore.kernel.org/r/20251224-enable-byte-cntr-for-ctcu-v9-0-886c4496fed4@oss.qualcomm.com

Changes in v9:
1. Drop the patch: add a new API to retrieve the helper device
2. Add a new patch to refactor the tmc_etr_get_catu_device function,
   making it generic to support all types of helper devices associated with ETR.
3. Optimizing the code for creating irq_threshold sysfs node.
4. Remove interrupt-name property and obtain the IRQ based on the
   in-port number.
Link to v8: https://lore.kernel.org/r/20251211-enable-byte-cntr-for-ctcu-v8-0-3e12ff313191@oss.qualcomm.com

Changes in V8:
1. Optimizing the patch 1 and patch 2 according to Suzuki's comments.
2. Combine the patch 3 and patch 4 together.
3. Rename the interrupt-name to prevent confusion, for example:etr0->etrirq0.
Link to V7 - https://lore.kernel.org/all/20251013-enable-byte-cntr-for-ctcu-v7-0-e1e8f41e15dd@oss.qualcomm.com/

Changes in V7:
1. rebased on tag next-20251010
2. updated info for sysfs node document
Link to V6 - https://lore.kernel.org/all/20250908-enable-byte-cntr-for-tmc-v6-0-1db9e621441a@oss.qualcomm.com/

Changes in V6:
1. rebased on next-20250905.
2. fixed the issue that the dtsi file has re-named from sa8775p.dtsi to
   lemans.dtsi.
3. fixed some minor issues about comments.
Link to V5 - https://lore.kernel.org/all/20250812083731.549-1-jie.gan@oss.qualcomm.com/

Changes in V5:
1. Add Mike's reviewed-by tag for patchset 1,2,5.
2. Remove the function pointer added to helper_ops according to Mike's
   comment, it also results the patchset has been removed.
3. Optimizing the paired create/clean functions for etr_buf_list.
4. Remove the unneeded parameter "reading" from the etr_buf_node.
Link to V4 - https://lore.kernel.org/all/20250725100806.1157-1-jie.gan@oss.qualcomm.com/

Changes in V4:
1. Rename the function to coresight_get_in_port_dest regarding to Mike's
comment (patch 1/10).
2. Add lock to protect the connections regarding to Mike's comment
(patch 2/10).
3. Move all byte-cntr functions to coresight-ctcu-byte-cntr file.
4. Add tmc_read_ops to wrap all read operations for TMC device.
5. Add a function in helper_ops to check whether the byte-cntr is
enabkled.
6. Call byte-cntr's read_ops if byte-cntr is enabled when reading data
from the sysfs node.
Link to V3 resend - https://lore.kernel.org/all/20250714063109.591-1-jie.gan@oss.qualcomm.com/

Changes in V3 resend:
1. rebased on next-20250711.
Link to V3 - https://lore.kernel.org/all/20250624060438.7469-1-jie.gan@oss.qualcomm.com/

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/

To: Suzuki K Poulose <suzuki.poulose@arm.com>
To: Mike Leach <mike.leach@arm.com>
To: James Clark <james.clark@linaro.org>
To: Alexander Shishkin <alexander.shishkin@linux.intel.com>
To: Rob Herring <robh@kernel.org>
To: Krzysztof Kozlowski <krzk+dt@kernel.org>
To: Conor Dooley <conor+dt@kernel.org>
To: Tingwei Zhang <tingwei.zhang@oss.qualcomm.com>
To: Bjorn Andersson <andersson@kernel.org>
To: Konrad Dybcio <konradybcio@kernel.org>
Cc: coresight@lists.linaro.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-arm-msm@vger.kernel.org
Cc: devicetree@vger.kernel.org
Signed-off-by: Jie Gan <jie.gan@oss.qualcomm.com>

---
Jie Gan (7):
      coresight: core: refactor ctcu_get_active_port and make it generic
      coresight: tmc: add create/clean functions for etr_buf_list
      coresight: tmc: introduce tmc_sysfs_ops to wrap sysfs read operations
      coresight: etr: add a new function to retrieve the CTCU device
      dt-bindings: arm: add an interrupt property for Coresight CTCU
      coresight: ctcu: enable byte-cntr for TMC ETR devices
      arm64: dts: qcom: lemans: add interrupts to CTCU device

 .../ABI/testing/sysfs-bus-coresight-devices-ctcu   |   9 +
 .../bindings/arm/qcom,coresight-ctcu.yaml          |  10 +
 arch/arm64/boot/dts/qcom/lemans.dtsi               |   3 +
 drivers/hwtracing/coresight/Makefile               |   2 +-
 drivers/hwtracing/coresight/coresight-core.c       |  24 ++
 .../hwtracing/coresight/coresight-ctcu-byte-cntr.c | 286 +++++++++++++++++++++
 drivers/hwtracing/coresight/coresight-ctcu-core.c  | 123 +++++++--
 drivers/hwtracing/coresight/coresight-ctcu.h       |  79 +++++-
 drivers/hwtracing/coresight/coresight-priv.h       |   2 +
 drivers/hwtracing/coresight/coresight-tmc-core.c   |  55 ++--
 drivers/hwtracing/coresight/coresight-tmc-etr.c    | 226 +++++++++++++++-
 drivers/hwtracing/coresight/coresight-tmc.h        |  42 +++
 12 files changed, 789 insertions(+), 72 deletions(-)
---
base-commit: a0ae2a256046c0c5d3778d1a194ff2e171f16e5f
change-id: 20260309-enable-byte-cntr-for-ctcu-ff86e6198b7f

Best regards,
-- 
Jie Gan <jie.gan@oss.qualcomm.com>

On 3/23/2026 5:49 PM, Jie Gan wrote:
> The byte-cntr function provided by the CTCU device is used to count the
> trace data entering the ETR. An interrupt is triggered 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,
> for example:
> /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 1 > /sys/bus/coresight/devices/ctcu0/irq_enabled0
> 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_enabled0
> 
> ---
> Changes in v16:
> 1. Remove lock/unlock processes in patch "coresight: tmc: add create/clean
>     functions for etr_buf_list" because we are allocating/freeing memory.
> - Link to v15: https://lore.kernel.org/r/20260313-enable-byte-cntr-for-ctcu-v15-0-1777f14ed319@oss.qualcomm.com
> 


Gentle ping


> Changes in v15:
> 1. add lockdep_assert_held in patch "coresight: tmc: add create/clean
>     functions for etr_buf_list"
> 2. optimize tmc_clean_etr_buf_list function
> 3. optimize the patch "enable byte-cntr for TMC ETR devices" according
>     to Suzuki's comments
>     - call byte_cntr_sysfs_ops from etr_sysfs_ops
>     - optimize the lock usage in all functions
>     - remove the buf_node parameter in etr_drvdata, move it to
>       byte_cntr_data
>     - move the tmc_reset_sysfs_buf function to tmc-etr.c
>     - add a read flag to struct etr_buf_node to allow updating pos while
>       traversing etr_buf_list during data reads.
> Link to v14: https://lore.kernel.org/r/20260309-enable-byte-cntr-for-ctcu-v14-0-c08823e5a8e6@oss.qualcomm.com
> 
> Changes in V14:
> 1. Drop the patch: integrate byte-cntr's sysfs_ops with tmc sysfs file_ops
> 2. Replace tmc_sysfs_ops with byte_cntr_sysfs_ops in byte_cntr_start
>     function and restore etr_sysfs_ops in byte_cntr_unprepare function.
> 3. Remove redundant checks in byte‑cntr functions.
> Link to V13: https://lore.kernel.org/all/20260223-enable-byte-cntr-for-ctcu-v13-0-9cb44178b250@oss.qualcomm.com/
> 
> Changes in v13:
> 1. initilize the byte_cntr_data->raw_spin_lock before using.
> 2. replace kzalloc with kzalloc_obj.
> Link to V12: https://lore.kernel.org/all/20260203-enable-byte-cntr-for-ctcu-v12-0-7bf81b86b70e@oss.qualcomm.com/
> 
> Changes in v12:
> 1. Add a new function for retrieving the CTCU's coresight_dev instead of
>     refactor the existing function.
> Link to v11: https://lore.kernel.org/r/20260126-enable-byte-cntr-for-ctcu-v11-0-c0af66ba15cf@oss.qualcomm.com
> 
> Changes in v11:
> 1. Correct the description in patch1 for the function coresight_get_in_port.
> 2. Renaming the sysfs_ops to tmc_sysfs_ops per Suzuki's suggestion.
> Link to v10: https://lore.kernel.org/r/20260122-enable-byte-cntr-for-ctcu-v10-0-22978e3c169f@oss.qualcomm.com
> 
> Changes in v10:
> 1. fix a free memory issue that is reported by robot for patch 2.
> Link to v9: https://lore.kernel.org/r/20251224-enable-byte-cntr-for-ctcu-v9-0-886c4496fed4@oss.qualcomm.com
> 
> Changes in v9:
> 1. Drop the patch: add a new API to retrieve the helper device
> 2. Add a new patch to refactor the tmc_etr_get_catu_device function,
>     making it generic to support all types of helper devices associated with ETR.
> 3. Optimizing the code for creating irq_threshold sysfs node.
> 4. Remove interrupt-name property and obtain the IRQ based on the
>     in-port number.
> Link to v8: https://lore.kernel.org/r/20251211-enable-byte-cntr-for-ctcu-v8-0-3e12ff313191@oss.qualcomm.com
> 
> Changes in V8:
> 1. Optimizing the patch 1 and patch 2 according to Suzuki's comments.
> 2. Combine the patch 3 and patch 4 together.
> 3. Rename the interrupt-name to prevent confusion, for example:etr0->etrirq0.
> Link to V7 - https://lore.kernel.org/all/20251013-enable-byte-cntr-for-ctcu-v7-0-e1e8f41e15dd@oss.qualcomm.com/
> 
> Changes in V7:
> 1. rebased on tag next-20251010
> 2. updated info for sysfs node document
> Link to V6 - https://lore.kernel.org/all/20250908-enable-byte-cntr-for-tmc-v6-0-1db9e621441a@oss.qualcomm.com/
> 
> Changes in V6:
> 1. rebased on next-20250905.
> 2. fixed the issue that the dtsi file has re-named from sa8775p.dtsi to
>     lemans.dtsi.
> 3. fixed some minor issues about comments.
> Link to V5 - https://lore.kernel.org/all/20250812083731.549-1-jie.gan@oss.qualcomm.com/
> 
> Changes in V5:
> 1. Add Mike's reviewed-by tag for patchset 1,2,5.
> 2. Remove the function pointer added to helper_ops according to Mike's
>     comment, it also results the patchset has been removed.
> 3. Optimizing the paired create/clean functions for etr_buf_list.
> 4. Remove the unneeded parameter "reading" from the etr_buf_node.
> Link to V4 - https://lore.kernel.org/all/20250725100806.1157-1-jie.gan@oss.qualcomm.com/
> 
> Changes in V4:
> 1. Rename the function to coresight_get_in_port_dest regarding to Mike's
> comment (patch 1/10).
> 2. Add lock to protect the connections regarding to Mike's comment
> (patch 2/10).
> 3. Move all byte-cntr functions to coresight-ctcu-byte-cntr file.
> 4. Add tmc_read_ops to wrap all read operations for TMC device.
> 5. Add a function in helper_ops to check whether the byte-cntr is
> enabkled.
> 6. Call byte-cntr's read_ops if byte-cntr is enabled when reading data
> from the sysfs node.
> Link to V3 resend - https://lore.kernel.org/all/20250714063109.591-1-jie.gan@oss.qualcomm.com/
> 
> Changes in V3 resend:
> 1. rebased on next-20250711.
> Link to V3 - https://lore.kernel.org/all/20250624060438.7469-1-jie.gan@oss.qualcomm.com/
> 
> 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/
> 
> To: Suzuki K Poulose <suzuki.poulose@arm.com>
> To: Mike Leach <mike.leach@arm.com>
> To: James Clark <james.clark@linaro.org>
> To: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> To: Rob Herring <robh@kernel.org>
> To: Krzysztof Kozlowski <krzk+dt@kernel.org>
> To: Conor Dooley <conor+dt@kernel.org>
> To: Tingwei Zhang <tingwei.zhang@oss.qualcomm.com>
> To: Bjorn Andersson <andersson@kernel.org>
> To: Konrad Dybcio <konradybcio@kernel.org>
> Cc: coresight@lists.linaro.org
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-arm-msm@vger.kernel.org
> Cc: devicetree@vger.kernel.org
> Signed-off-by: Jie Gan <jie.gan@oss.qualcomm.com>
> 
> ---
> Jie Gan (7):
>        coresight: core: refactor ctcu_get_active_port and make it generic
>        coresight: tmc: add create/clean functions for etr_buf_list
>        coresight: tmc: introduce tmc_sysfs_ops to wrap sysfs read operations
>        coresight: etr: add a new function to retrieve the CTCU device
>        dt-bindings: arm: add an interrupt property for Coresight CTCU
>        coresight: ctcu: enable byte-cntr for TMC ETR devices
>        arm64: dts: qcom: lemans: add interrupts to CTCU device
> 
>   .../ABI/testing/sysfs-bus-coresight-devices-ctcu   |   9 +
>   .../bindings/arm/qcom,coresight-ctcu.yaml          |  10 +
>   arch/arm64/boot/dts/qcom/lemans.dtsi               |   3 +
>   drivers/hwtracing/coresight/Makefile               |   2 +-
>   drivers/hwtracing/coresight/coresight-core.c       |  24 ++
>   .../hwtracing/coresight/coresight-ctcu-byte-cntr.c | 286 +++++++++++++++++++++
>   drivers/hwtracing/coresight/coresight-ctcu-core.c  | 123 +++++++--
>   drivers/hwtracing/coresight/coresight-ctcu.h       |  79 +++++-
>   drivers/hwtracing/coresight/coresight-priv.h       |   2 +
>   drivers/hwtracing/coresight/coresight-tmc-core.c   |  55 ++--
>   drivers/hwtracing/coresight/coresight-tmc-etr.c    | 226 +++++++++++++++-
>   drivers/hwtracing/coresight/coresight-tmc.h        |  42 +++
>   12 files changed, 789 insertions(+), 72 deletions(-)
> ---
> base-commit: a0ae2a256046c0c5d3778d1a194ff2e171f16e5f
> change-id: 20260309-enable-byte-cntr-for-ctcu-ff86e6198b7f
> 
> Best regards,