Re: [PATCH v3 00/10] Coresight: Add support for TPDM and TPDA

[Mike Leach]

Hello  Mao,

I have looked through this set and have a few general questions.

My understanding based on the information in the code is that the TPDM
devices will always send data to the TPDA device, the TPDM is not
capable of directly driving the ATB itself?
The TPDA device  will then packetize the inputs and output these to
the ATB over the normal CoreSight architecture to a standard ETR / ETF
for collection.

Looking at the TPDM driver - it is assigned a trace ID but never
actually uses it in the hardware. My assumption here is that this is
used purely to satisfy the requirement that the CoreSight core has
that all sources have a unique trace id?

For the TPDA driver you assign an ATID as an attribute in device tree,
and then program this into the devices control register.

The trace IDs in ETM / ETE / STM, are programmed into the hardware and
these values drive the ATID value on the trace bus. So assigning an
ATID value to the TPDA driver through device tree will lead to clashes
with the assignment of trace IDs in the other driver software.

The topology here appears to me that you have multiple  "data source"
devices TPDM, supplying a TPDA - which is the real CoreSight "trace
source" from the viewpoint of the trace bus and CoreSight
infrastructure.
To get this to work in the current CoreSight driver stack, you have
assigned the TPDM as a source type, and the TPDA as a link to ensure
that when a TPDM is started, all the components on the path to the
sink are activated.
This is fine.

If my assumptions above are all accurate I suggest the following improvements

For TPDA drop the device tree assignment of ATID and instead use the
coresight_get_system_trace_id() function you introduce in the 2nd
patch in this set.

For TPDM you have assigned a unique source sub-type
CORESIGHT_DEV_SUBTYPE_SOURCE_SYS.- this could become
CORESIGHT_DEV_SUBTYPE_SOURCE_DATA_ONLY. If the trace ID assigned to
this device is only to satisfy the unique ID requirement and is not
used elsewhere, then the sub type could become
CORESIGHT_DEV_SUBTYPE_SOURCE_DATA_ONLY. We can agree that this sub
type does not need a unique ID and acts as none ATB a source for
another component, The core code can be altered to drop the
requirement for this sub-type and trace ID can be dropped for this
component.

You should be aware that we are in the process of re-designed how
trace IDs are allocated. The current mechanism does not scale for
large multi-core systems (currently broken for any system > 46 cores),
and as you have discovered there is a need for additional allocation
of IDs. Also the ETE / TRBE combination does not need a trace ID.  A
dynamic allocation system is being proposed.

Regards

Mike


On Wed, 9 Feb 2022 at 10:57, Mao Jinlong <quic_jinlmao@xxxxxxxxxxx> wrote:
>
> This series adds support for the trace performance monitoring and
> diagnostics hardware (TPDM and TPDA). It is composed of two major
> elements.
> a) Changes for original coresight framework to support for TPDM and TPDA.
> b) Add driver code for TPDM and TPDA.
>
> Introduction of changes for original coresight framework
> Support TPDM as new coresight source.
> Since only STM and ETM are supported as coresight source originally.
> TPDM is a newly added coresight source. We need to change
> the original way of saving coresight path to support more types source
> for coresight driver.
> The following patch is to add support more coresight sources.
>     Use IDR to maintain all the enabled sources' paths.
>     coresight: Use bitmap to assign trace id to the sources
>
> Introduction of TPDM and TPDA
> TPDM - The trace performance monitoring and diagnostics monitor or TPDM in
> short serves as data collection component for various dataset types
> specified in the QPMDA(Qualcomm performance monitoring and diagnostics
> architecture) spec. The primary use case of the TPDM is to collect data
> from different data sources and send it to a TPDA for packetization,
> timestamping and funneling.
>     Coresight: Add coresight TPDM source driver
>     dt-bindings: arm: Adds CoreSight TPDM hardware definitions
>     coresight-tpdm: Add DSB dataset support
>     coresight-tpdm: Add integration test support
>     docs: sysfs: coresight: Add sysfs ABI documentation for TPDM
>
> TPDA - The trace performance monitoring and diagnostics aggregator or
> TPDA in short serves as an arbitration and packetization engine for the
> performance monitoring and diagnostics network as specified in the QPMDA
> (Qualcomm performance monitoring and diagnostics architecture)
> specification. The primary use case of the TPDA is to provide
> packetization, funneling and timestamping of Monitor data as specified
> in the QPMDA specification.
> The following patch is to add driver for TPDA.
>     Coresight: Add TPDA link driver
>     dt-bindings: arm: Adds CoreSight TPDA hardware definitions
>
> The last patch of this series is a device tree modification, which add
> the TPDM and TPDA configuration to device tree for validating.
>     ARM: dts: msm: Add coresight components for SM8250
>
> Once this series patches are applied properly, the tpdm and tpda nodes
> should be observed at the coresight path /sys/bus/coresight/devices
> e.g.
> /sys/bus/coresight/devices # ls -l | grep tpd
> tpda0 -> ../../../devices/platform/soc@0/6004000.tpda/tpda0
> tpdm0 -> ../../../devices/platform/soc@0/6c08000.mm.tpdm/tpdm0
>
> We can use the commands are similar to the below to validate TPDMs.
> Enable coresight sink first.
>
> echo 1 > /sys/bus/coresight/devices/tmc_etf0/enable_sink
> echo 1 > /sys/bus/coresight/devices/tpdm0/enable_source
> echo 1 > /sys/bus/coresight/devices/tpdm0/integration_test
> echo 2 > /sys/bus/coresight/devices/tpdm0/integration_test
> The test data will be collected in the coresight sink which is enabled.
> If rwp register of the sink is keeping updating when do
> integration_test (by cat tmc_etf0/mgmt/rwp), it means there is data
> generated from TPDM to sink.
>
> Changes from V2:
> 1. Use bitmap to assign the trace id. (Mathieu Poirier)
>
> Mao Jinlong (10):
>   Use IDR to maintain all the enabled sources' paths.
>   coresight: Use bitmap to assign trace id to the sources
>   Coresight: Add coresight TPDM source driver
>   dt-bindings: arm: Adds CoreSight TPDM hardware definitions
>   coresight-tpdm: Add DSB dataset support
>   coresight-tpdm: Add integration test support
>   docs: sysfs: coresight: Add sysfs ABI documentation for TPDM
>   Coresight: Add TPDA link driver
>   dt-bindings: arm: Adds CoreSight TPDA hardware definitions
>   ARM: dts: msm: Add coresight components for SM8250
>
>  .../testing/sysfs-bus-coresight-devices-tpdm  |   6 +
>  .../bindings/arm/coresight-tpda.yaml          | 129 ++++
>  .../bindings/arm/coresight-tpdm.yaml          |  81 ++
>  .../devicetree/bindings/arm/coresight.txt     |   7 +
>  MAINTAINERS                                   |   1 +
>  .../arm64/boot/dts/qcom/sm8250-coresight.dtsi | 690 ++++++++++++++++++
>  arch/arm64/boot/dts/qcom/sm8250.dtsi          |   2 +
>  drivers/hwtracing/coresight/Kconfig           |  33 +
>  drivers/hwtracing/coresight/Makefile          |   2 +
>  drivers/hwtracing/coresight/coresight-core.c  | 127 ++--
>  drivers/hwtracing/coresight/coresight-tpda.c  | 193 +++++
>  drivers/hwtracing/coresight/coresight-tpda.h  |  32 +
>  drivers/hwtracing/coresight/coresight-tpdm.c  | 270 +++++++
>  drivers/hwtracing/coresight/coresight-tpdm.h  |  57 ++
>  include/linux/coresight-pmu.h                 |  11 +
>  include/linux/coresight.h                     |   1 +
>  16 files changed, 1592 insertions(+), 50 deletions(-)
>  create mode 100644 Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
>  create mode 100644 Documentation/devicetree/bindings/arm/coresight-tpda.yaml
>  create mode 100644 Documentation/devicetree/bindings/arm/coresight-tpdm.yaml
>  create mode 100644 arch/arm64/boot/dts/qcom/sm8250-coresight.dtsi
>  create mode 100644 drivers/hwtracing/coresight/coresight-tpda.c
>  create mode 100644 drivers/hwtracing/coresight/coresight-tpda.h
>  create mode 100644 drivers/hwtracing/coresight/coresight-tpdm.c
>  create mode 100644 drivers/hwtracing/coresight/coresight-tpdm.h
>
> --
> 2.17.1
>


--
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK