linux-kernel - Re: [PATCH] Documentation: coresight: Update the generic device names

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Date:   Mon, 3 Jun 2019 13:01:33 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        leo.yan@...aro.org, coresight@...ts.linaro.org,
        Jonathan Corbet <corbet@....net>
Subject: Re: [PATCH] Documentation: coresight: Update the generic device names

Hi Suzuki,

On Thu, May 30, 2019 at 04:11:17PM +0100, Suzuki K Poulose wrote:
> Update the documentation to reflect the new naming scheme with
> latest changes.
> 
> Reported-by: Leo Yan <leo.yan@...aro.org>
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Cc: Jonathan Corbet <corbet@....net>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
>  Documentation/trace/coresight.txt | 34 +++++++++++++++++++---------------
>  1 file changed, 19 insertions(+), 15 deletions(-)
> 
> diff --git a/Documentation/trace/coresight.txt b/Documentation/trace/coresight.txt
> index efbc832..7b427cf 100644
> --- a/Documentation/trace/coresight.txt
> +++ b/Documentation/trace/coresight.txt
> @@ -326,16 +326,20 @@ 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@...aro-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@...alhost:/sys/bus/event_source/devices/cs_etm/sinks# ls
> +	tmc_etf0  tmc_etr0  tpiu0
>  
> -	root@...aro-nano:~# perf record -e cs_etm/@...70000.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@...alhost:/sys/bus/coresight/devices# ls
> +	etm0  etm1  etm2  etm3  etm4  etm5  funnel0  funnel1  funnel2  replicator0  stm0 tmc_etf0  tmc_etr0  tpiu0
> +
> +	root@...aro-nano:~# perf record -e cs_etm/@..._etr0/u --per-thread program

On the "older" kernels you are referring to one would find the original naming
convention.  Everything else looks good to me.

Mathieu

>  
>  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 +356,7 @@ 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/@...70000.etr/u --per-thread
> +    perf record -e cs_etm/@..._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 +385,7 @@ 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/@...70000.etr/u --per-thread taskset -c 2 ./sort
> +	$ perf record -e cs_etm/@..._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 +409,7 @@ 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@...ericarmv8:~# ls /sys/bus/coresight/devices/20100000.stm
> +root@...ericarmv8:~# ls /sys/bus/coresight/devices/stm0
>  enable_source   hwevent_select  port_enable     subsystem       uevent
>  hwevent_enable  mgmt            port_select     traceid
>  root@...ericarmv8:~#
> @@ -413,14 +417,14 @@ root@...ericarmv8:~#
>  Like any other source a sink needs to be identified and the STM enabled before
>  being used:
>  
> -root@...ericarmv8:~# echo 1 > /sys/bus/coresight/devices/20010000.etf/enable_sink
> -root@...ericarmv8:~# echo 1 > /sys/bus/coresight/devices/20100000.stm/enable_source
> +root@...ericarmv8:~# echo 1 > /sys/bus/coresight/devices/tmc_etf0/enable_sink
> +root@...ericarmv8:~# 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@...ericarmv8:~# ls -l /dev/20100000.stm
> -crw-------    1 root     root       10,  61 Jan  3 18:11 /dev/20100000.stm
> +root@...ericarmv8:~# ls -l /dev/stm0
> +crw-------    1 root     root       10,  61 Jan  3 18:11 /dev/stm0
>  root@...ericarmv8:~#
>  
>  Details on how to use the generic STM API can be found here [2].
> -- 
> 2.7.4
>