From mboxrd@z Thu Jan 1 00:00:00 1970 From: Graeme Russ Date: Mon, 16 May 2011 16:11:29 +1000 Subject: [U-Boot] [PATCH 0/4] Accurate boot time measurement In-Reply-To: <20110516055503.81F381491B07@gemini.denx.de> References: <1305319923-9477-1-git-send-email-sjg@chromium.org> <20110515115317.56695DB7945@gemini.denx.de> <20110516055503.81F381491B07@gemini.denx.de> Message-ID: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On Mon, May 16, 2011 at 3:55 PM, Wolfgang Denk wrote: > Dear Graeme Russ, > > In message 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