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Message-ID: <06d76546-badc-4035-8954-4c3e13d2fb22@oss.qualcomm.com>
Date: Mon, 27 Oct 2025 09:12:10 +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>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>,
Tingwei Zhang <tingwei.zhang@....qualcomm.com>,
Yuanfang Zhang <yuanfang.zhang@....qualcomm.com>,
Mao Jinlong <jinlong.mao@....qualcomm.com>,
Jie Gan
<quic_jiegan@...cinc.com>,
Bjorn Andersson <andersson@...nel.org>,
Konrad Dybcio <konradybcio@...nel.org>
Cc: 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,
Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Subject: Re: [PATCH v7 0/9] coresight: ctcu: Enable byte-cntr function for TMC
ETR
On 10/13/2025 1:49 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 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
>
Gentle reminder.
Thanks,
Jie
> 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/
>
> Signed-off-by: Jie Gan <jie.gan@....qualcomm.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: lemans: Add interrupts to CTCU device
>
> .../ABI/testing/sysfs-bus-coresight-devices-ctcu | 6 +
> .../bindings/arm/qcom,coresight-ctcu.yaml | 17 +
> arch/arm64/boot/dts/qcom/lemans.dtsi | 5 +
> drivers/hwtracing/coresight/Makefile | 2 +-
> drivers/hwtracing/coresight/coresight-core.c | 59 ++++
> .../hwtracing/coresight/coresight-ctcu-byte-cntr.c | 368 +++++++++++++++++++++
> drivers/hwtracing/coresight/coresight-ctcu-core.c | 108 ++++--
> drivers/hwtracing/coresight/coresight-ctcu.h | 62 +++-
> drivers/hwtracing/coresight/coresight-priv.h | 4 +
> drivers/hwtracing/coresight/coresight-tmc-core.c | 104 ++++--
> drivers/hwtracing/coresight/coresight-tmc-etr.c | 112 +++++++
> drivers/hwtracing/coresight/coresight-tmc.h | 37 +++
> 12 files changed, 825 insertions(+), 59 deletions(-)
> ---
> base-commit: 2b763d4652393c90eaa771a5164502ec9dd965ae
> change-id: 20251013-enable-byte-cntr-for-ctcu-6199b791b77a
>
> Best regards,
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