[U-Boot] 83xx and LCRR setting

[Kim Phillips]

On Mon, 24 Aug 2009 12:15:39 +0200
Detlev Zundel <dzu at denx.de> wrote:

> > but I can do of course a:
> >
> > +	/* LCRR - Clock Ratio Register (10.3.1.14) */
> > +	im->lbus.lcrr = (im->lbus.lcrr & ~LCRR_MASK) | \
> > +			(CONFIG_SYS_LCRR & LCRR_MASK);
> >
> > Which way is prefered?
> 
> Personally I'd prefer the latter, as I expect a bitmask to specifiy
> which bits I'm allowed to _write_.

which is consistent with the rest of the assignment style in that file.

> >>> This really depends if and how this applies to the other members of the
> >>> 83xx family.
> >> 
> >> they're all the same, really.
> >
> > OK, if it is so ;-)
> 
> Then why not put this into mpc83xx.h?

that makes a lot of sense - I don't know why original code has multiple
#ifdef configuration based sccr assignments in cpu_init.c.

> >>> And, by the way, we should _really_ be using accessor macros all around
> >>> ;)
> >> 
> >> actually LCRR itself has specific instructions that say if written, it
> >> then should be read, and then an isync be issued.
> >
> > Hmm.. actual code did not this! Where is this documented? And shouldn;t
> > we update this in code?
> 
> Of course "we" should update this ;)

of course.

Heiko, I got tired of looking up all the errata docs for common parts
of 83xx, so now I look at the latest device manuals.  In this case, the
source was "MPC8379E PowerQUICC II Pro Integrated Host Processor Family
Reference Manual, Rev. 1", p. 10-34, in the description for the CLKDIV
bitfield.

let's not duplicate existing bad code, and use the io accessor fns
(e.g., out_be, etc.) for new code here please.

Thanks,

Kim