Subject: Re: uartlite with 2.6.17 kernel and kernel early text messages

From: "David H. Lynch Jr." <[email-masked]>
Date: Sun, 15 Oct 2006 18:00:58 -0400

Michael Galassi wrote:
>> In an effort to get past the "Rebooting to System ACE Configuration
>> Address 6..." message, I have selected "support for early boot texts
>> over serial port" in kernel debugging.
>>     
>
> This will not work.  Unfortunately linux here shows its roots as PS OS,
> there is a vast amount of hardcoded NS8250/NS16550 knowledge in there.
> I'd started modularizing this so we could use a UART lite but the more I
> dug the lower my motivation.  This is really ugly code in an area that
> is of virtually no interest.  For now get rid of support for early boot
> texts over serial port" and use your JTAG to read the buffers if you
> panic before the console is up and running.
>   
   UartLite early boot text support is fairly trivial. It is also fairly 
standalone.
    You basically need about 5 lines  of code to output a character.
   
    David Bolcsfoldi has posted patches to Peter's driver that should work.
    I have had working early boot text support long before I even had a 
working driver.
    There is atleast one other Uart family besides the 8250 with early 
boot text support.
     You can also fairly trivially fold my early boot text code into 
Peter's driver.
   
    The most disconcerting problem is the #ifdef that results with 
something like 4 or cases.

    The non-8250 support could be more modularized - but it still not a 
major pain.

> -michael
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-- 
Dave Lynch 					  	    DLA Systems
Software Development:  				         Embedded Linux
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