[PATCH v5 0/9] coresight: ctcu: Enable byte-cntr function for TMC ETR

[Jie Gan]

On 8/12/2025 4:37 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.
> 


Just a gentle reminder to ensure the patch series hasn't been overlooked 
due to the high volume of message.

Thanks,
Jie


> 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 0x10000 > /sys/bus/coresight/devices/ctcu0/irq_threshold
> echo 1 > /sys/bus/coresight/devices/tmc_etr0/enable_sink
> echo 1 > /sys/bus/coresight/devices/etm0/enable_source
> cat /dev/tmc_etr0
> 
> Enable both ETR0 and ETR1:
> echo 0x10000 0x10000 > /sys/bus/coresight/devices/ctcu0/irq_threshold
> 
> Reset the BYTECNTR register for etr0:
> echo 0 > /sys/bus/coresight/devices/ctcu0/irq_threshold
> 
> 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/
> 
> Jie Gan (9):
>    coresight: core: Refactoring ctcu_get_active_port and make it generic
>    coresight: core: add a new API to retrieve the helper device
>    coresight: tmc: add etr_buf_list to store allocated etr_buf
>    coresight: tmc: add create/clean functions for etr_buf_list
>    coresight: tmc: Introduce sysfs_read_ops to wrap sysfs read operations
>    dt-bindings: arm: add an interrupt property for Coresight CTCU
>    coresight: ctcu: enable byte-cntr for TMC ETR devices
>    coresight: tmc: integrate byte-cntr's read_ops with sysfs file_ops
>    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  |  59 +++
>   .../coresight/coresight-ctcu-byte-cntr.c      | 368 ++++++++++++++++++
>   .../hwtracing/coresight/coresight-ctcu-core.c | 108 +++--
>   drivers/hwtracing/coresight/coresight-ctcu.h  |  62 ++-
>   drivers/hwtracing/coresight/coresight-priv.h  |   4 +
>   .../hwtracing/coresight/coresight-tmc-core.c  | 104 +++--
>   .../hwtracing/coresight/coresight-tmc-etr.c   | 110 ++++++
>   drivers/hwtracing/coresight/coresight-tmc.h   |  39 ++
>   12 files changed, 824 insertions(+), 59 deletions(-)
>   create mode 100644 Documentation/ABI/testing/sysfs-bus-coresight-devices-ctcu
>   create mode 100644 drivers/hwtracing/coresight/coresight-ctcu-byte-cntr.c
>