Hi Wolfgang,
On Dec 15, 2012 6:30 PM, "Wolfgang Denk" wd@denx.de wrote:
Dear Graeme Russ,
In message 50CBD313.60508@gmail.com you wrote:
I can give you an example - Remote Telemetry Units (RTUs). They usually have a number of serial ports. The number of ports may vary based on the sub-model. Some ports may be RS-232, some may be RS-485 or RS-422. Depending on what additional devices you want to communicate with, you
may
need to use the 'console/diag' port to connect to a real device. So what you want to do is route console to another port (if available) or even netconsole.
Netconsole is always an option, and I think we also support switching to other serial ports here and there (after relocation, that is).
But if you need console output before relocation (i. e. during debugging), then I do not see why we cannot demand that the console port is statically configured, and that you need corectly configured images to have an early working console.
I have seen situations where console output by the bootloader messes up attached serial devices hence effectively dropping the serial port count by one. Pre-console buffer helps a lot (no console output until we know where to send it to). But that kills early debug.
I do get your point of view. But I think a combination of storing the dynamic console info in a DT format, the pre-console buffer and getting
DT
available as early as possible can yield a 'non-cludgy' solution. For
board
or SoC vendors who, for whatever reason, have implemented non-DT
storage of
hardware enumeration data they will be stuck with the penalty of having
to
translate that data into DT format before it can be parsed by U-Boot.
Maybe
this could be done in SPL. Yes, it's a hack, but if it can't be worked around, push it as low as possible and as far away from the U-Boot core
as
possible
I mostly agree here. But I still fail to see why we havet os upport this combination of early and dynamic - and only this is what causes some issues.
The situations I have seen can be resolved by pre-console buffer and console configured in env. If the hardware is playing up, a factory reset to default console (without using pre-console buffer) suffices (the device is on the bench with nothing attached). But then we are back to the board specific/pre-DT problem.
Regards,
Graeme