[U-Boot] Strange / Unreadable console output

[Andreas Bießmann]

Dear Markus Hubig,

On 14.08.2012 11:08, Markus Hubig wrote:
> On Tue, Aug 14, 2012 at 08:22:11AM +0200, Andreas Bießmann wrote:
>> On 27.07.12 11:16, Markus Hubig wrote:
>>> one minor Problem I often read about in this list is some crappy / unreadable
>>> console output at beginning of the U-Boot start procedure. Now I have the same
>>> "visual" Problem.
>>>
>>> | H�NAND:  128 MiB
>>> | *** Warning - bad CRC, using default environment
>>> | 
>>> | In:    serial
>>> | Out:   serial
>>> | Err:   serial
>>> | Net:   macb0
>>> | macb0: Starting autonegotiation...
>>> | macb0: Autonegotiation timed out (status=0x7849)
>>> | macb0: link down (status: 0x7849)
>>> | Hit any key to stop autoboot:  0 
>>> | ...
> 
> <snipp>
> 
>>>
>>> Has anyone an ideea how to fix this? Or what's the cause of it? Is it even
>>> related to u-boot or is it something at91bootstrap is doing wrong?
>>
>> can you please check http://patchwork.ozlabs.org/patch/107896/
>>
>> It seems this patch was set to 'Accepted' but never applied to the
>> master repository. Unfortunately this got lost in nirvana end of last
>> year. I will apply it in any case but can you please check if it fixes
>> your problem?
> 
> Unfortunately not ... but it dosen't do any harm.

How sad!

I wonder if this has something to do with the ominous PC9. It is
possible that this PC9 switches some vital element e.g. power supply,
'output enable' of UART level shifter or something else which needs some
settling. Have you tried adding some delay in between setting this pin
and activating the serial port output pins?
Did you investigate the PCB? Which device is directly behind the DB9
connector? Can you find a datasheet for that device and check if it has
some power saving features? Can you check if these power saving features
switched with the PC9? Did taskit respond to your request for detailed
information?

Another possible reason can be the fact that you enable the output pins
after serial port is enabled (serial_init runs way before board_init).
Therefore your output is put into the TX register but I don't know what
happens then. Eventually the output is delayed until the output pins are
enabled in conjunction with the 'SYS' clock. Maybe the TX logic is
happily shifting the bits into nirvana until you switch on the output
pins. In conjunction with the PC9 thing this could be your problem.

best regards

Andreas Bießmann