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SubjectRe: [PATCH] Documentation: coresight: Update the generic device names
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Hi Leo,

>>>> 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 ($SYSFS)/bus/coresight/devices/:
>>>> +
>>>> + root@localhost:/sys/bus/coresight/devices# ls
>>>> + etm0 etm1 etm2 etm3 etm4 etm5 funnel0 funnel1 funnel2 replicator0 stm0 tmc_etf0 tmc_etr0 tpiu0
>>>> +
>>>> + root@linaro-nano:~# perf record -e cs_etm/@tmc_etr0/u --per-thread program
>>>
>>> On the "older" kernels you are referring to one would find the original naming
>>> convention. Everything else looks good to me.
>>
>> True, but do we care what we see there ? All we care about is the location,
>> where to find them. I could fix it, if you think thats needed.
>
> IIUC, either the old kernel or newer kernel, both we can find the event
> from ($SYSFS)/bus/event_source/devices/cs_etm/sinks/; the only
> difference between them is the naming convention.

The cs_etm/sinks was only added with the CPU-wide trace support. So, if someone
refers to this document alone and then tries to do something on on older kernel,
which is quite possible for a production device running a stable kernel, {s,}he
might be surprised.

>
> So the doc can use the same location to find event for both new and
> old kernel, and explain the naming convention difference?

My question is really, does the naming convention matter ? What you see
under the directory is the name. But yes, I am open to add a section to
explain the fact that we changed the naming scheme, if everyone agrees
to it.

Cheers
Suzuki

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