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From:   Avri Altman <Avri.Altman@wdc.com>
To:     Adrian Hunter <adrian.hunter@intel.com>,
        "Martin K . Petersen" <martin.petersen@oracle.com>,
        "James E . J . Bottomley" <jejb@linux.ibm.com>
CC:     "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Alim Akhtar <alim.akhtar@samsung.com>,
        Bean Huo <huobean@gmail.com>, Can Guo <cang@codeaurora.org>,
        Stanley Chu <stanley.chu@mediatek.com>
Subject: RE: [PATCH V2 1/4] scsi: ufs: Add exception event tracepoint
Thread-Topic: [PATCH V2 1/4] scsi: ufs: Add exception event tracepoint
Thread-Index: AQHW/qxDGTHS29mllEOWiXxyvmFw/6pRsiFw
Date:   Wed, 10 Feb 2021 18:09:23 +0000
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 <20210209062437.6954-2-adrian.hunter@intel.com>
In-Reply-To: <20210209062437.6954-2-adrian.hunter@intel.com>
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>=20
> Currently, exception event status can be read from wExceptionEventStatus
> attribute (sysfs file attributes/exception_event_status under the UFS hos=
t
> controller device directory). Polling that attribute to track UFS excepti=
on
> events is impractical, so add a tracepoint to track exception events for
> testing and debugging purposes.
>=20
> Note, by the time the exception event status is read, the exception event
> may have cleared, so the value can be zero - see example below.
>=20
> Note also, only enabled exception events can be reported. A subsequent
> patch adds the ability for users to enable selected exception events via
> debugfs.
>=20
> Example with driver instrumented to enable all exception events:
>=20
>   # echo 1 >
> /sys/kernel/debug/tracing/events/ufs/ufshcd_exception_event/enable
>=20
>   ... do some I/O ...
>=20
>   # cat /sys/kernel/debug/tracing/trace
>   # tracer: nop
>   #
>   # entries-in-buffer/entries-written: 3/3   #P:5
>   #
>   #                                _-----=3D> irqs-off
>   #                               / _----=3D> need-resched
>   #                              | / _---=3D> hardirq/softirq
>   #                              || / _--=3D> preempt-depth
>   #                              ||| /     delay
>   #           TASK-PID     CPU#  ||||   TIMESTAMP  FUNCTION
>   #              | |         |   ||||      |         |
>        kworker/2:2-173     [002] ....   731.486419: ufshcd_exception_even=
t:
> 0000:00:12.5: status 0x0
>        kworker/2:2-173     [002] ....   732.608918: ufshcd_exception_even=
t:
> 0000:00:12.5: status 0x4
>        kworker/2:2-173     [002] ....   732.609312: ufshcd_exception_even=
t:
> 0000:00:12.5: status 0x4
>=20
> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Avri Altman <avri.altman@wdc.com>