[U-Boot] [RFC] command/cache: Add flush_cache command

[Scott Wood <scottwood@freescale.com>]

On 03/20/2013 07:27:29 PM, Michael Cashwell wrote:
> On Mar 20, 2013, at 7:48 PM, Scott Wood <scottwood@freescale.com>  
> wrote:
> 
> > On 03/20/2013 06:33:41 PM, Michael Cashwell wrote:
> >
> >> What is the purpose of limiting the memory range to be flushed? Is  
> there a reason one might want to NOT flush certain data sitting in a  
> dirty cache line out to memory before doing a go or boot command?
> >
> > Because it would take a while to flush all of RAM?
> 
> "Flushing all of RAM" is what trips me up. Fundamentally, that puts  
> the cart in front of the horse. The goal isn't to flush all of RAM  
> but rather to flush all of cache.

Right, I was just responding to your question of, "What is the purpose  
of limiting the memory range to be flushed?"

> Iterating over the small thing rather than the large would seem  
> reasonably efficient.
> 
> But as you say, if there are architectures where that can't be done  
> and you must pass GBs of physical address space (rather than KB of  
> cache space) through some process then range limiting it does make  
> sense.

Right.  The range specified is a minimum to be flushed -- if a  
particular architecture finds it easier/quicker to flush everything  
instead, that's fine.

-Scott