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

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Date:   Wed, 1 Mar 2023 23:04:14 +0800
From:   Jinlong Mao <quic_jinlmao@...cinc.com>
To:     Mike Leach <mike.leach@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>
CC:     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 Mike & Suzuki,

On 2/9/2023 10:56 PM, Mike Leach wrote:
> 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

There is also requirement that reset all the sources and sinks in an 
user space daemon.
For such requirement, I think it is better to use only once sysfs node 
instead of iterating through coresight/device folder in an user space 
daemon.

Thanks
Jinlong Mao

>> Thanks
>> Jinlong Mao
>>
>>>
>
>