[U-Boot] [PATCH 0/4] Accurate boot time measurement

[Graeme Russ]

On Mon, May 16, 2011 at 3:55 PM, Wolfgang Denk <wd at denx.de> wrote:
> Dear Graeme Russ,
>
> In message <BANLkTim7=-rZa_L-Dy0B-+aDqv4ngOLb-g at mail.gmail.com> you wrote:
>>
>> But at 9600 baud it is over 1ms - 9600 is still considered the lowest
>> common denominator for serial comms for diagnostic output for a lot of
>> devices such as industrial PLCs etc.
>
> I think in the last 5 years I have seen but 2 devices using 9600 bps.
> All others appear to be using 115200 bps these days.
>
> And even at 9600 we're still close to millisecond reolution...
>
>> And in the field, you may be interested more in transient timing anomalies
>> which may result from network issues if the device is obtaining an IP address
>> or loading an image file. In such scenarios, you will need to log the boot
>> timing of every boot, not just when a serial terminal is connected
>
> time-stamping console output is not restricted to the serial port.  It
> works as well with tty over USB, or netconsole, or even netconsole
> over USB.

My point is, if the device reboots in the field, you cannot recover the
boot timing analysis as once it is streamed out it is gone forever

>
>> And finally, the lack of a serial port is a biggie - There are devices out
>> there that do not have serial ports
>
> If they have a console interface, then the output can be time-stamped.

See above

Regards,

Graeme