lkml.org 
[lkml]   [2019]   [Jun]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH v2] Documentation: coresight: Update the generic device names
On Mon, 10 Jun 2019 at 12:02, Suzuki K Poulose <suzuki.poulose@arm.com> wrote:
>
> Update the documentation to reflect the new naming scheme with
> latest changes.
>
> Reported-by: Leo Yan <leo.yan@linaro.org>
> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
> Changes since v1
> - Add a section about the Device Naming scheme and add refer to
> it in the examples.
> ---
> Documentation/trace/coresight.txt | 82 ++++++++++++++++++++++++++++++++-------
> 1 file changed, 67 insertions(+), 15 deletions(-)
>
> diff --git a/Documentation/trace/coresight.txt b/Documentation/trace/coresight.txt
> index efbc832..b027d61 100644
> --- a/Documentation/trace/coresight.txt
> +++ b/Documentation/trace/coresight.txt
> @@ -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

This looks goo do me. Jonathan, if you prefer to handle this via your tree:

Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>

Otherwise I'll pick it up.

Thanks,
Mathieu

> +
> +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].
> --
> 2.7.4
>

\
 
 \ /
  Last update: 2019-06-11 17:58    [W:0.065 / U:5.140 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site