Re: [PATCH 1/2] Documentation: tracing: Documentation for ultrasoc SMB drivers

From: Mathieu Poirier
Date: Mon Sep 06 2021 - 13:34:53 EST

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On Mon, Jul 19, 2021 at 07:17:36PM +0800, Qi Liu wrote:
> Ultrasoc trace module is a system level solution for tracing, and SMB
> is the component in trace module to store trace message. This patch
> brings in a documentation for ultrasoc SMB driver and simple introduces
> how to use ultrasoc SMB by sysfs interface and perf interface.
>
> Signed-off-by: Qi Liu <liuqi115@xxxxxxxxxx>
> ---
> .../trace/coresight/ultrasoc-trace.rst | 193 ++++++++++++++++++
> 1 file changed, 193 insertions(+)
> create mode 100644 Documentation/trace/coresight/ultrasoc-trace.rst
>
> diff --git a/Documentation/trace/coresight/ultrasoc-trace.rst b/Documentation/trace/coresight/ultrasoc-trace.rst
> new file mode 100644
> index 000000000000..dee133e27bf3
> --- /dev/null
> +++ b/Documentation/trace/coresight/ultrasoc-trace.rst
> @@ -0,0 +1,193 @@
> +=======================================================
> +Siemens Embedded Analytics - HW Assisted Tracing on SoC
> +=======================================================
> + :Author: Jonathan Zhou <Jonathan.zhouwen@xxxxxxxxxx>
> + Qi Liu <liuqi115@xxxxxxxxxx>
> + :Date: July 8th, 2021
> +
> +Introduction
> +------------
> +
> +This document is concerned with the Siemens Embedded Analytics Framework,
> +using for tracing of multiple type SoC. As this module is developed by
> +Ultrasoc technology, which is acquired by Siemens, we still use "Ultrasoc"
> +to name document and structures.
> +
> +System Memory Buffer is an important component in this Analytics Framework,
> +it provides a way to buffer and store messages in system memory. It provides
> +a capability to store messages received on its input message interface to an
> +area of system memory.
> +
> +A typical Siemens trace system would look like the following diagram:
> + @@@@@@@@@@@@@
> + @ CPU @
> + @@@@@@@@@@@@@
> + #############
> + # Coresight #
> + # ETM #
> + #######
> + ###
> + #
> + |
> + *
> + *******************************
> + *** AMBA Advanced Trace Bus (ATB) ***
> + ***************^***************
> + =============== |
> + === FUNNEL ==<--- |
> + =======
> + |
> + *
> + @@@@@@@
> + @ TRC @
> + @@@@@
> + @@@
> + @
> + |
> + *
> + ************************************** *******************
> + ************************ Message BUS ***************************
> + ******************^************************^****************
> + | |
> + @@@@@@@@@@@@@@@@@@ | @@@@@@@@@@@@
> + @ Message Engine @ | @ JTAG COM @
> + @@@@@@@@@@@@@@@@@@ | @@@@@@@@@@
> + | |---> @@@@@@@@
> + | @@@@@@
> + @@@@@@@ |
> + @ SMB @ JTAG
> + @@@@@
> + @@@
> + @
> + |
> + |
> + *
> + ***************************************************************
> + **************************** AMBA AXI ****************************
> + *****************************************************************
> +
> +Acronyms
> +---------------------------
> +
> +Acronyms:
> +
> +SMB: System Memory Buffer
> +TRC: Trace receiver
> +
> +Framework and implementation
> +------------------------------
> +
> +SMB is implemented as platform device, each SCCL has one SMB device.
> +
> +As TRC receives data from coresight ETM device, SMB can use the following API
> +to register into coresight framework as a sink device:
> +.. c:function:: struct coresight_device *coresight_register(struct coresight_desc *desc);
> +.. c:function:: void coresight_unregister(struct coresight_device *csdev);
> +
> +Then users can get trace data by this path: ETM->funnel->SMB.
> +More information about coresight framework can be found in
> +Documention/trace/coresight/coresight.rst.
> +
> +If everything goes well, the relationship of Embedded Analytics devices will be
> +described under the sysfs::
> +
> + $# ls /sys/bus/platform/devices/
> + <HID.smb>:00
> + $# ls /sys/bus/coresight/devices/
> + etm0 etm14 etm2 etm25 etm30 etm8 funnel4
> + etm1 etm15 etm20 etm26 etm31 etm9 funnel5
> + etm10 etm16 etm21 etm27 etm4 funnel0 funnel6
> + etm11 etm17 etm22 etm28 etm5 funnel1 funnel7
> + etm12 etm18 etm23 etm29 etm6 funnel2 sink_smb0
> + etm13 etm19 etm24 etm3 etm7 funnel3
> + $# ls -l /sys/bus/coresight/devices/funnel0/connections/
> + <file details> in:0 -> ../../../../system/cpu/cpu0/ARMHC500:00/etm0
> + <file details> in:1 -> ../../../../system/cpu/cpu1/ARMHC500:01/etm1
> + <file details> in:2 -> ../../../../system/cpu/cpu2/ARMHC500:02/etm2
> + <file details> in:3 -> ../../../../system/cpu/cpu3/ARMHC500:03/etm3
> + <file details> nr_links
> + <file details> out:0 -> ../../../HISI0391:00/HISI03A1:00/sink_smb0
> + $# ls -l /sys/bus/coresight/devices/sink_smb0/connections/
> + <file details> in:101 -> ../../../../ARMHC9FE:05/funnel5
> + <file details> in:114 -> ../../../../ARMHC9FE:07/funnel7
> + <file details> in:121 -> ../../../../ARMHC9FE:03/funnel3
> + <file details> in:39 -> ../../../../ARMHC9FE:00/funnel0
> + <file details> in:51 -> ../../../../ARMHC9FE:04/funnel4
> + <file details> in:61 -> ../../../../ARMHC9FE:06/funnel6
> + <file details> in:68 -> ../../../../ARMHC9FE:02/funnel2
> + <file details> in:89 -> ../../../../ARMHC9FE:01/funnel1
> + <file details> nr_links
> +
> +How to use the Embedded Analytics trace module
> +-----------------------------------------------
> +
> +There are two ways to use the Embedded Analytics trace module:
> +
> +1. interacting directly with the devices using the sysFS interface.
> +2. using the perf cmd line tools.
> +
> +1) Using the sysFS interface:
> +
> +Before trace collection can start, a coresight sink needs to be identified.
> +There is no limit on the amount of sinks (nor sources) that can be enabled at
> +any given moment. As a generic operation, all device pertaining to the sink
> +class will have an "active" entry in sysfs::
> +
> + $# ls /sys/bus/coresight/devices/
> + etm0 etm14 etm2 etm25 etm30 etm8 funnel4
> + etm1 etm15 etm20 etm26 etm31 etm9 funnel5
> + etm10 etm16 etm21 etm27 etm4 funnel0 funnel6
> + etm11 etm17 etm22 etm28 etm5 funnel1 funnel7
> + etm12 etm18 etm23 etm29 etm6 funnel2 sink_smb0
> + etm13 etm19 etm24 etm3 etm7 funnel3
> + $# ls /sys/bus/coresight/devices/sink_smb0
> + connections enable_sink firmware_node power subsystem uevent
> + $# echo 1 > /sys/bus/coresight/devices/sink_smb0/enable_sink
> + $# cat /sys/bus/coresight/devices/sink_smb0/enable_sink
> + 1
> +
> +When start trace collection, etm devices corresponding to the enabled sink
> +should be selected::
> +
> + $# echo 1 > /sys/bus/coresight/devices/etm0/enable_source
> + $# cat /sys/bus/coresight/devices/etm0/enable_source
> + 1
> + $# cat /sys/bus/platform/devices/<HID.smb>:00/com_status
> + com-type : DOWN-ONLY
> + service status : stopped
> + interrupt status : 0x00000003
> + write point : 0x5437f400 <----- The write pointer is moving
> +
> +Trace collection is stopped the same way::
> +
> + $# echo 0 > /sys/bus/coresight/devices/etm0/enable_source
> + $# echo 0 > /sys/bus/coresight/devices/sink_smb0/enable_sink
> +
> +The content of the SMB buffer can be harvested directly from /dev::
> +
> + $# dd if=/dev/sink_smb0 of=~/cstrace.bin
> + 5233+0 records in
> + 5233+0 records out
> + 2679296 bytes (2.7 MB) copied, 0.0131708 s, 203 MB/s
> +
> + root:/sys/bus/coresight/devices#
> +
> +The file cstrace.bin can be decompressed using "ptm2human".
> +
> +2) Using perf framework:
> +
> +As SMB device has been registered with coresight framework, perf tool can be
> +used to control Embedded Analytics trace collection, and the method is similar
> +to using perf to do coresight trace collection.
> +
> +The only thing to note is, list of cpus should be correspond to the specified
> +sink device.
> +
> +Example usage of perf::
> +
> + $# ./perf list pmu
> + cs_etm// [Kernel PMU event]
> + $# ./perf record -e cs_etm/@sink_smb0/ -C 0 --per-thread sleep 2s
> + [ perf record: Woken up 2 times to write data ]
> + [ perf record: Captured and wrote 0.288 MB perf.data ]
> + $# ./perf report

This IP block works like any other sink device and as such I don't really see a
need for this documentation - especially since it is mostly conveying the same
information already present in coresight.rst.

Thanks,
Mathieu

> --
> 2.17.1
>

Next message: Miklos Szeredi: "Re: [syzbot] linux-next test error: KASAN: null-ptr-deref Read in fuse_conn_put"
Previous message: Ulf Hansson: "Re: [PATCH 1/3] PM: domains: Drop the performance state vote for a device at detach"
Next in thread: liuqi (BA): "Re: [PATCH 1/2] Documentation: tracing: Documentation for ultrasoc SMB drivers"
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