[PATCH v5 0/5] Coresight: Add Coresight TMC Control Unit driver

[Jie Gan]

The Coresight TMC Control Unit(CTCU) device hosts miscellaneous configuration
registers to control various features related to TMC ETR device.

The CTCU device works as a helper device physically connected to the TMC ETR device.
---------------------------------------------------------
             |ETR0|             |ETR1|
              . \                 / .
              .  \               /  .
              .   \             /   .
              .    \           /    .
---------------------------------------------------
ETR0ATID0-ETR0ATID3     CTCU    ETR1ATID0-ETR1ATID3
---------------------------------------------------
Each ETR has four ATID registers with 128 bits long in total.
e.g. ETR0ATID0-ETR0ATID3 registers are used by ETR0 device.

Based on the trace id which is programed in CTCU ATID register of
specific ETR, trace data with that trace id can get into ETR's buffer
while other trace data gets ignored. The number of CTCU ATID registers
depends on the number of defined TMC ETR devices. For example, two TMC
ETR devices need eight ATID registers. ETR0 with ETR0ATID0-ETR0ATID3
and ETR1 with ETR1ATID0-ETRATID3.

The significant challenge in enabling the data filter function is how
to collect the trace ID of the source device. The introduction of
trace_id callback function addresses this challenge. The callback function
collects trace ID of the device and return it back. The trace ID will be
stored in the structure called cs_sink_data and transmitted to helper
and sink devices.

The cs_sink_data structure is created to address how to transmit
parameters needs by coresight_enable_path/coresight_disbale_path
functions.

Here is an example of the struct cs_sink_data:
struct cs_sink_data {
        struct perf_output_handle  *handle; //used by perf mode
        struct coresight_device    *sink;   //used to retrieve atid_offset
        u32                        traceid; //traceid needed by CTCU
};

The atid_offset mentioned before is the offset to ATID register in CTCU
device.

Enabling the source device will configure one bit in the ATID register based
on its trace ID.
Disabling the source devices will reset the bit in the AITD register
based on its trace ID.

Useage:
Enable:
STM device with trace ID 5 and ETR0 is activated.
Bitmap before the enablement:
ETR0ATID0:
31..................543210
==========================
0000000000000000000000...0
==========================

Bitmap after the enablement:
31..................543210
==========================
0000000000000...0000100000
==========================

The bit 5 of the ETR0ATID0 register is configured to 1 when enabling the
STM device.

Disable:
STM device with trace ID 5 and ETR0 is activated.
Bitmap before the disablement:
ETR0ATID0:
31................6543210
=========================
000000000010111...0100000
=========================

Bitmap after the disablement
ETR0ATID0:
31................6543210
=========================
000000000010111...0000000
=========================

The bit 5 of the ETR0ATID0 register is reset to 0 when disabling the STM
device.

Previous discussion for V1:
https://lore.kernel.org/lkml/20240618072726.3767974-1-quic_jiegan@xxxxxxxxxxx/T/#t

Changes in V2:
1. Rename the device to Coresight Control Unit.
2. Introduce the trace_id function pointer to address the challeng how to
properly collect the trace ID of the device.
3. Introduce a new way to define the qcom,ccu-atid-offset property in
device tree.
4. Disabling the filter function blocked on acquiring the ATID-offset,
which will be addressed in a separate patch once it’s ready.

Previous discussion for V2:
https://lore.kernel.org/linux-arm-msm/20240705090049.1656986-1-quic_jiegan@xxxxxxxxxxx/T/#t

Changes in V3:
1. Rename the device to Coresight TMC Control Unit(CTCU).
2. Introduce a new way to define the platform related configs. The new
   structure, qcom_ctcu_config, is used to store configurations specific
   to a platform. Each platform should have its own qcom_ctcu_config structure.
3. In perf mode, the ETM devices allocate their trace IDs using the
   perf_sink_id_map. In sysfs mode, the ETM devices allocate their trace
   IDs using the id_map_default.
4. Considering the scenario where both ETR devices might be enabled simultaneously
   with multiple sources, retrieving and using trace IDs instead of id_map is more effective
   for the CTCU device in sysfs mode. For example, We can configure one ETR as sink for high
   throughput trace data like ETM and another ETR for low throughput trace data like STM.
   In this case, STM data won’t be flushed out by ETM data quickly. However, if we use id_map to
   manage the trace IDs, we need to create a separate id_map for each ETR device. Addtionally, We
   would need to iterate through the entire id_map for each configuration.
5. Add support for apb's clock name "apb". If the function fails to obtain the clock with
   the name "apb_pclk", it will attempt to acquire the clock with the name "apb".

Previous discussion for V3:
https://lore.kernel.org/linux-arm-kernel/20240812024141.2867655-1-quic_jiegan@xxxxxxxxxxx/

Changes in V4:
1. Add TMC description in binding file.
2. Restrict the number of ports for the CTCU device to a range of 0 to 1 in the binding file,
because the maximum number of CTCU devices is 2 for existing projects.

Changes in V5:
1. Fix the format issue for description paragrah in dt binding file.
2. Previous discussion for why use "in-ports" property instead of "ports".
Please help to comment this point if the platform driver must be fixed before
submit this patch series.
https://lore.kernel.org/linux-arm-msm/4b51d5a9-3706-4630-83c1-01b01354d9a4@xxxxxxx/

Jie Gan (5):
  Coresight: Add support for new APB clock name
  Coresight: Add trace_id function to retrieving the trace ID
  dt-bindings: arm: Add Coresight TMC Control Unit hardware
  Coresight: Add Coresight TMC Control Unit driver
  arm64: dts: qcom: Add CTCU and ETR nodes for SA8775p

 .../bindings/arm/qcom,coresight-ctcu.yaml     |  84 +++++
 arch/arm64/boot/dts/qcom/sa8775p.dtsi         | 160 ++++++++++
 drivers/hwtracing/coresight/Kconfig           |   8 +
 drivers/hwtracing/coresight/Makefile          |   1 +
 drivers/hwtracing/coresight/coresight-core.c  |  59 +++-
 drivers/hwtracing/coresight/coresight-ctcu.c  | 292 ++++++++++++++++++
 drivers/hwtracing/coresight/coresight-ctcu.h  |  21 ++
 drivers/hwtracing/coresight/coresight-etb10.c |   3 +-
 .../hwtracing/coresight/coresight-etm-perf.c  |  37 ++-
 .../coresight/coresight-etm3x-core.c          |  30 ++
 .../coresight/coresight-etm4x-core.c          |  29 ++
 drivers/hwtracing/coresight/coresight-priv.h  |  13 +-
 drivers/hwtracing/coresight/coresight-stm.c   |  22 ++
 drivers/hwtracing/coresight/coresight-sysfs.c |  24 +-
 .../hwtracing/coresight/coresight-tmc-etf.c   |   3 +-
 .../hwtracing/coresight/coresight-tmc-etr.c   |   6 +-
 drivers/hwtracing/coresight/coresight-tpda.c  |  20 ++
 drivers/hwtracing/coresight/coresight-trbe.c  |   4 +-
 drivers/hwtracing/coresight/ultrasoc-smb.c    |   3 +-
 include/linux/coresight.h                     |  16 +-
 20 files changed, 807 insertions(+), 28 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/arm/qcom,coresight-ctcu.yaml
 create mode 100644 drivers/hwtracing/coresight/coresight-ctcu.c
 create mode 100644 drivers/hwtracing/coresight/coresight-ctcu.h

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2.34.1