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Subject: Re: [PATCH 1/4] scsi: ufs: Add exception event tracepoint
From:   Bean Huo <huobean@gmail.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-kernel@vger.kernel.org,
        Alim Akhtar <alim.akhtar@samsung.com>,
        Avri Altman <avri.altman@wdc.com>,
        Can Guo <cang@codeaurora.org>,
        Stanley Chu <stanley.chu@mediatek.com>
Date:   Wed, 03 Feb 2021 09:37:40 +0100
In-Reply-To: <20210119141542.3808-2-adrian.hunter@intel.com>
References: <20210119141542.3808-1-adrian.hunter@intel.com>
         <20210119141542.3808-2-adrian.hunter@intel.com>
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On Tue, 2021-01-19 at 16:15 +0200, Adrian Hunter wrote:
> Currently, exception event status can be read from
> wExceptionEventStatus
> attribute (sysfs file attributes/exception_event_status under the UFS
> host
> controller device directory). Polling that attribute to track UFS
> exception
> events is impractical, so add a tracepoint to track exception events
> for
> testing and debugging purposes.
> 
> 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.
> 
> Note also, only enabled exception events can be reported. A
> subsequent
> patch adds the ability for users to enable selected exception events
> via
> debugfs.
> 
> Example with driver instrumented to enable all exception events:
> 
>   # echo 1 >
> /sys/kernel/debug/tracing/events/ufs/ufshcd_exception_event/enable
> 
>   ... do some I/O ...
> 
>   # cat /sys/kernel/debug/tracing/trace
>   # tracer: nop
>   #
>   # entries-in-buffer/entries-written: 3/3   #P:5
>   #
>   #                                _-----=> irqs-off
>   #                               / _----=> need-resched
>   #                              | / _---=> hardirq/softirq
>   #                              || / _--=> preempt-depth
>   #                              ||| /     delay
>   #           TASK-PID     CPU#  ||||   TIMESTAMP  FUNCTION
>   #              | |         |   ||||      |         |
>        kworker/2:2-173     [002] ....   731.486419:
> ufshcd_exception_event: 0000:00:12.5: exception event status 0x0
>        kworker/2:2-173     [002] ....   732.608918:
> ufshcd_exception_event: 0000:00:12.5: exception event status 0x4
>        kworker/2:2-173     [002] ....   732.609312:
> ufshcd_exception_event: 0000:00:12.5: exception event status 0x4

Hi Adrian

aAbove print has two trace strings "exception event" in each event
print, it is somehow redundant to me, why not replace the second one
with the event string name?


ufshcd_exception_event: 0000:00:12.5: LOW_TEMP 0x4

or just status:

ufshcd_exception_event: 0000:00:12.5: status 0x4


Bean

> 

>