Question about DBCR0 initialization for 440

[Josh Boyer]

On Fri, Apr 17, 2009 at 02:41:26PM -0600, John Linn wrote:
> 
>
>> -----Original Message-----
>> From: Josh Boyer [mailto:jwboyer at linux.vnet.ibm.com] 
>> Sent: Friday, April 17, 2009 2:36 PM
>> To: John Linn
>> Cc: grant.likely at secretlab.ca; Benjamin Herrenschmidt; 
>> linuxppc-dev at ozlabs.org; Hollis Blanchard; Tirumala Reddy Marri
>> Subject: Re: Question about DBCR0 initialization for 440
>> 
>> On Fri, Apr 17, 2009 at 02:30:45PM -0600, John Linn wrote:
>> >> > Might be worth checking if external debug is enabled, and 
>> >> override it
>> >> > only if it's not.
>> >> 
>> >> ppc440x5_um.pdf says that both can be enabled.
>> >> 
>> >
>> >The code that I started the thread with, from the fsl file, 
>> has conditional for the BDI around it.
>> >
>> >We think that we still need that conditional as the code is 
>> not Oring in the enable such that it would
>> >disable external debug mode for the BDI. But we need it this 
>> way for our Xilinx pod.
>> 
>> EDM is a read-only bit according to the docs I have.  You 
>> can't set it (or
>> clear it) at all.  It's only set by external hardware.
>
>That's strange, my 440x4_um.pdf does not say it's read-only unless it's
>in some obscure place.

Gah.  I think that was my mistake.  I don't see that in x4 or x5 manuals, but
it came up on IRC.

josh