Messages in this thread | | | Subject | Re: [PATCH] Documentation: coresight: Update the generic device names | From | Suzuki K Poulose <> | Date | Fri, 7 Jun 2019 09:40:48 +0100 |
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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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