linux-kernel - Re: Time stamp value in printk records

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Date:   Mon, 30 Sep 2019 09:53:54 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Sodagudi Prasad <psodagud@...eaurora.org>
Cc:     pmladek@...e.com, sergey.senozhatsky@...il.com,
        linux-kernel@...r.kernel.org
Subject: Re: Time stamp value in printk records

On Mon, 30 Sep 2019 06:33:42 -0700
Sodagudi Prasad <psodagud@...eaurora.org> wrote:

> Hi All,
> 
>  From Qualcomm side, we would like to check with upstream team about 
> adding Raw time stamp value to printk records. On Qualcomm soc, there 
> are various DSPs subsystems are there - for example audio, video and 
> modem DSPs.
> Adding raw timer value(along with sched_clock()) in the printk record 
> helps in the following use cases –
> 1)	To find out which subsystem  crashed first  -  Whether application 
> processor crashed first or DSP subsystem?
> 2)	If there are any system stability issues on the DSP side, what is the 
> activity on the APPS processor side during that time?
> 
> Initially during the device boot up, printk shed_clock value can be 
> matched with timer raw value used on the dsp subsystem, but after APPS 
> processor suspends several times, we don’t have way to correlate the 
> time stamp  value on the DSP and APPS processor. All timers(both apps 
> processor timer and dsp timers) are derived from globally always on 
> timer on Qualcomm soc, So keeping global timer raw values in printk 
> records and dsp logs help to correlate the activity of all the 
> processors in SoC.
> 
> It would be great if upstream team adds common solution this problem if 
> all soc vendors would get benefit by adding raw timer value to  printk 
> 

Hi Prasad,

If you or someone you know would like to present patches for exactly
what you would like to see, that would go a long way.

-- Steve