[PATCH v2 0/4] Coresight: Add Coresight Control Unit driver

[Jie Gan]

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

The CCU device works as a helper device physically connected to the TMC ETR device.
---------------------------------------------------------
             |ETR0|             |ETR1|
              . \                 / .
              .  \               /  .
              .   \             /   .
              .    \           /    .
---------------------------------------------------
ETR0ATID0-ETR0ATID3     CCU     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 CCU 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 CCU 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 directly. 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 CCU
};

The atid_offset mentioned before is the offset to ATID register in CCU
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@quicinc.com/T/#t

V1->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.

Jie Gan (4):
  Coresight: Add trace_id function to collect trace ID
  dt-bindings: arm: Add binding document for Coresight Control Unit
    device.
  Coresight: Add Coresight Control Unit driver
  arm64: dts: qcom: Add CCU and ETR nodes for SA8775p

 .../bindings/arm/qcom,coresight-ccu.yaml      |  87 ++++++
 arch/arm64/boot/dts/qcom/sa8775p.dtsi         | 163 ++++++++++
 drivers/hwtracing/coresight/Kconfig           |   6 +
 drivers/hwtracing/coresight/Makefile          |   1 +
 drivers/hwtracing/coresight/coresight-ccu.c   | 290 ++++++++++++++++++
 drivers/hwtracing/coresight/coresight-ccu.h   |  18 ++
 drivers/hwtracing/coresight/coresight-core.c  |  53 +++-
 drivers/hwtracing/coresight/coresight-etb10.c |   3 +-
 .../hwtracing/coresight/coresight-etm-perf.c  |  34 +-
 .../coresight/coresight-etm3x-core.c          |  14 +
 .../coresight/coresight-etm4x-core.c          |  13 +
 drivers/hwtracing/coresight/coresight-priv.h  |  12 +-
 drivers/hwtracing/coresight/coresight-stm.c   |  13 +
 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  |  13 +
 drivers/hwtracing/coresight/coresight-trbe.c  |   4 +-
 drivers/hwtracing/coresight/ultrasoc-smb.c    |   3 +-
 include/linux/coresight.h                     |   4 +
 20 files changed, 739 insertions(+), 25 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/arm/qcom,coresight-ccu.yaml
 create mode 100644 drivers/hwtracing/coresight/coresight-ccu.c
 create mode 100644 drivers/hwtracing/coresight/coresight-ccu.h

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2.34.1