linux-kernel - Re: [PATCH] coresight: core: Add sysfs node to reset all sources and sinks

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Message-ID: <CAJ9a7Vh08A8b7YLF=pYPudB0CZ0XjEpF=4YHrNNd7xo_JQGYaA@mail.gmail.com>
Date:   Thu, 9 Feb 2023 14:56:05 +0000
From:   Mike Leach <mike.leach@...aro.org>
To:     Jinlong Mao <quic_jinlmao@...cinc.com>
Cc:     Suzuki K Poulose <suzuki.poulose@....com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Tingwei Zhang <quic_tingweiz@...cinc.com>,
        Yuanfang Zhang <quic_yuanfang@...cinc.com>,
        Tao Zhang <quic_taozha@...cinc.com>,
        Hao Zhang <quic_hazha@...cinc.com>
Subject: Re: [PATCH] coresight: core: Add sysfs node to reset all sources and sinks

Hi,

On Thu, 9 Feb 2023 at 03:02, Jinlong Mao <quic_jinlmao@...cinc.com> wrote:
>
>
> On 2/9/2023 12:36 AM, Suzuki K Poulose wrote:
> > On 08/02/2023 16:20, Mike Leach wrote:
> >> Quick correction - you need to look for enable_source  / enable_sink
> >> files and disable those that are currently '1'
> >>
> >> Mike
> >>
> >> On Wed, 8 Feb 2023 at 16:16, Mike Leach <mike.leach@...aro.org> wrote:
> >>>
> >>> Hi
> >>>
> >>> As this is a sysfs only update - would it not be easier to simply use
> >>> a shell script to iterate through coresight/devices/ looking for
> >>> disable_source / disable_sink files and setting those accordingly?
> >>>
> >>> See tools/perf/tests/shell/test_arm_coresight.sh for an example of a
> >>> script that does similar iteration to test coresight in perf
> >>>
> >
> > +1
> >
> > Suzuki
>
> Hi Mike & Suzuki,
>
> Sometimes user just want to have some quick test from PC with adb commands.
> It is very easy to reset all sources and sinks' status by command below.
> echo 1 > /sys/bus/coresight/reset_source_sink
>

Users of coresight via sysfs will have to know how to use the
coresight infrastructure in order to enable the sources and sinks in
the first place -
e.g
echo 1 > /sys/bus/coresight/devices/tmc_etr0/enable_sink
echo 1 > /sys/bus/coresight/devices/etm0/enable_source

Given that they are aware of which sources and sinks they enabled -
disabling them should be simple.


> Preparing the script for test is not easy for users who are not familiar
> with the coresight framework.
>
If there is a genuine use case were a user has opened so many sources
on the command line that they need a simpler way of closing them than
repeating the enabled commands with an
echo 0 > ...
then any script could be shipped as part of kernel/tools/coresight or
kernel/samples/coresight - they would not have to write it themselves,
and just run it from the command line - for example :-
./kernel/tools/coresight/scripts/sysfs_disable_sources_and_sinks.sh

Realistically users will only try out a couple of devices as the
usefulness of the sysfs interface is really limited to testing or
board bring up.
Any complex use with sysfs - as in the coresight tests I mentioned
earlier is really going to be done by scripting.


Regards

Mike

> Thanks
> Jinlong Mao
>
> >
> >



-- 
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK