[RFC] "indirect" DCR access (40x, BookE)

Kumar Gala kumar.gala at motorola.com
Sat Mar 13 01:25:23 EST 2004

Look in u-boot.  They have some user commands that allow
reading/writing dcr's.  These commands are written with self modifying
code, I would recommend that we reuse that.

Also, it begs the question of should this be extended to SPRs, not that
I have come across a case with SPRs that I need to iterate over a large

- kumar

On Mar 11, 2004, at 10:54 PM, Eugene Surovegin wrote:

> On Thu, Mar 11, 2004 at 08:44:09PM -0800, Stephen Williams wrote:
>>>> I think you should just write it as self modifying code :-)
>>>> Write the instruction with the DCR number and just execute it.
>>> And deal with locking and icache/dcache coherency ?
>>> No, thanks :)
>> Actually, I recall that there is a code fixup mechanism that
>> is invoked early in kernel init that does exactly that: it
>> manages some machine specific differences by editing the code
>> in place in a safe way.
> Yes, you are correct, but this is done only once during startup and
> nobody cares how fast it is. BTW, there is no locking issues at this
> stage.
> I'm not saying that it's impossible :). It's just not very efficient
> to do such stuff on run-time (lock a spinlock, change memory, dcache
> flush, icache invalidate, isync...)
> Eugene.

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