mirror of
https://github.com/brain-hackers/linux-brain.git
synced 2024-06-09 23:36:23 +09:00
Documentation: coresight: Update the generic device names
Update the documentation to reflect the new naming scheme with latest changes. Reported-by: Leo Yan <leo.yan@linaro.org> Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Suzuki K Poulose
Jonathan Corbet
parent
83e8b971f8
commit
cd84d63a29
|
|
@ -188,6 +188,49 @@ specific to that component only. "Implementation defined" customisations are
|
|||
expected to be accessed and controlled using those entries.
|
||||
|
||||
|
||||
Device Naming scheme
|
||||
------------------------
|
||||
The devices that appear on the "coresight" bus were named the same as their
|
||||
parent devices, i.e, the real devices that appears on AMBA bus or the platform bus.
|
||||
Thus the names were based on the Linux Open Firmware layer naming convention,
|
||||
which follows the base physical address of the device followed by the device
|
||||
type. e.g:
|
||||
|
||||
root:~# ls /sys/bus/coresight/devices/
|
||||
20010000.etf 20040000.funnel 20100000.stm 22040000.etm
|
||||
22140000.etm 230c0000.funnel 23240000.etm 20030000.tpiu
|
||||
20070000.etr 20120000.replicator 220c0000.funnel
|
||||
23040000.etm 23140000.etm 23340000.etm
|
||||
|
||||
However, with the introduction of ACPI support, the names of the real
|
||||
devices are a bit cryptic and non-obvious. Thus, a new naming scheme was
|
||||
introduced to use more generic names based on the type of the device. The
|
||||
following rules apply:
|
||||
|
||||
1) Devices that are bound to CPUs, are named based on the CPU logical
|
||||
number.
|
||||
|
||||
e.g, ETM bound to CPU0 is named "etm0"
|
||||
|
||||
2) All other devices follow a pattern, "<device_type_prefix>N", where :
|
||||
|
||||
<device_type_prefix> - A prefix specific to the type of the device
|
||||
N - a sequential number assigned based on the order
|
||||
of probing.
|
||||
|
||||
e.g, tmc_etf0, tmc_etr0, funnel0, funnel1
|
||||
|
||||
Thus, with the new scheme the devices could appear as :
|
||||
|
||||
root:~# ls /sys/bus/coresight/devices/
|
||||
etm0 etm1 etm2 etm3 etm4 etm5 funnel0
|
||||
funnel1 funnel2 replicator0 stm0 tmc_etf0 tmc_etr0 tpiu0
|
||||
|
||||
Some of the examples below might refer to old naming scheme and some
|
||||
to the newer scheme, to give a confirmation that what you see on your
|
||||
system is not unexpected. One must use the "names" as they appear on
|
||||
the system under specified locations.
|
||||
|
||||
How to use the tracer modules
|
||||
-----------------------------
|
||||
|
||||
|
|
@ -326,16 +369,25 @@ amount of processor cores), the "cs_etm" PMU will be listed only once.
|
|||
A Coresight PMU works the same way as any other PMU, i.e the name of the PMU is
|
||||
listed along with configuration options within forward slashes '/'. Since a
|
||||
Coresight system will typically have more than one sink, the name of the sink to
|
||||
work with needs to be specified as an event option. Names for sink to choose
|
||||
from are listed in sysFS under ($SYSFS)/bus/coresight/devices:
|
||||
work with needs to be specified as an event option.
|
||||
On newer kernels the available sinks are listed in sysFS under:
|
||||
($SYSFS)/bus/event_source/devices/cs_etm/sinks/
|
||||
|
||||
root@linaro-nano:~# ls /sys/bus/coresight/devices/
|
||||
20010000.etf 20040000.funnel 20100000.stm 22040000.etm
|
||||
22140000.etm 230c0000.funnel 23240000.etm 20030000.tpiu
|
||||
20070000.etr 20120000.replicator 220c0000.funnel
|
||||
23040000.etm 23140000.etm 23340000.etm
|
||||
root@localhost:/sys/bus/event_source/devices/cs_etm/sinks# ls
|
||||
tmc_etf0 tmc_etr0 tpiu0
|
||||
|
||||
root@linaro-nano:~# perf record -e cs_etm/@20070000.etr/u --per-thread program
|
||||
On older kernels, this may need to be found from the list of coresight devices,
|
||||
available under ($SYSFS)/bus/coresight/devices/:
|
||||
|
||||
root:~# ls /sys/bus/coresight/devices/
|
||||
etm0 etm1 etm2 etm3 etm4 etm5 funnel0
|
||||
funnel1 funnel2 replicator0 stm0 tmc_etf0 tmc_etr0 tpiu0
|
||||
|
||||
root@linaro-nano:~# perf record -e cs_etm/@tmc_etr0/u --per-thread program
|
||||
|
||||
As mentioned above in section "Device Naming scheme", the names of the devices could
|
||||
look different from what is used in the example above. One must use the device names
|
||||
as it appears under the sysFS.
|
||||
|
||||
The syntax within the forward slashes '/' is important. The '@' character
|
||||
tells the parser that a sink is about to be specified and that this is the sink
|
||||
|
|
@ -352,7 +404,7 @@ perf can be used to record and analyze trace of programs.
|
|||
Execution can be recorded using 'perf record' with the cs_etm event,
|
||||
specifying the name of the sink to record to, e.g:
|
||||
|
||||
perf record -e cs_etm/@20070000.etr/u --per-thread
|
||||
perf record -e cs_etm/@tmc_etr0/u --per-thread
|
||||
|
||||
The 'perf report' and 'perf script' commands can be used to analyze execution,
|
||||
synthesizing instruction and branch events from the instruction trace.
|
||||
|
|
@ -381,7 +433,7 @@ sort example is from the AutoFDO tutorial (https://gcc.gnu.org/wiki/AutoFDO/Tuto
|
|||
Bubble sorting array of 30000 elements
|
||||
5910 ms
|
||||
|
||||
$ perf record -e cs_etm/@20070000.etr/u --per-thread taskset -c 2 ./sort
|
||||
$ perf record -e cs_etm/@tmc_etr0/u --per-thread taskset -c 2 ./sort
|
||||
Bubble sorting array of 30000 elements
|
||||
12543 ms
|
||||
[ perf record: Woken up 35 times to write data ]
|
||||
|
|
@ -405,7 +457,7 @@ than the program flow through the code.
|
|||
As with any other CoreSight component, specifics about the STM tracer can be
|
||||
found in sysfs with more information on each entry being found in [1]:
|
||||
|
||||
root@genericarmv8:~# ls /sys/bus/coresight/devices/20100000.stm
|
||||
root@genericarmv8:~# ls /sys/bus/coresight/devices/stm0
|
||||
enable_source hwevent_select port_enable subsystem uevent
|
||||
hwevent_enable mgmt port_select traceid
|
||||
root@genericarmv8:~#
|
||||
|
|
@ -413,14 +465,14 @@ root@genericarmv8:~#
|
|||
Like any other source a sink needs to be identified and the STM enabled before
|
||||
being used:
|
||||
|
||||
root@genericarmv8:~# echo 1 > /sys/bus/coresight/devices/20010000.etf/enable_sink
|
||||
root@genericarmv8:~# echo 1 > /sys/bus/coresight/devices/20100000.stm/enable_source
|
||||
root@genericarmv8:~# echo 1 > /sys/bus/coresight/devices/tmc_etf0/enable_sink
|
||||
root@genericarmv8:~# echo 1 > /sys/bus/coresight/devices/stm0/enable_source
|
||||
|
||||
From there user space applications can request and use channels using the devfs
|
||||
interface provided for that purpose by the generic STM API:
|
||||
|
||||
root@genericarmv8:~# ls -l /dev/20100000.stm
|
||||
crw------- 1 root root 10, 61 Jan 3 18:11 /dev/20100000.stm
|
||||
root@genericarmv8:~# ls -l /dev/stm0
|
||||
crw------- 1 root root 10, 61 Jan 3 18:11 /dev/stm0
|
||||
root@genericarmv8:~#
|
||||
|
||||
Details on how to use the generic STM API can be found here [2].
|
||||
|
|
|
|||
Loading…
Reference in New Issue
Block a user