[U-Boot] ARM v7: Flush icache when executing a program with go

[Wolfgang Denk]

Dear Henrik Nordström,

In message <1368792981.765.21.camel at localhost> you wrote:
> 
> > There is a common, architecture-independent C API that implements
> > cache flushing/invalidation; please re-read the summary at [1]
> 
> Sorry I missed that discussion. Had a bit too much mail for a while.

No problem; that's why I pointed you to the sumnmary (and the rest of
the thread).

> > The cache commands currently do not support subcommands for flushing
> > / invalidating the caches.  See again [1].
> 
> From what I see the cache commands do have a sub commands for flushing.
> 
> "icache flush" calls icache_invalidate_all().
> 
> "dcache flush" calls flush_dcache_all().

Indeed. I was not aware of this :-(

> but imho the user shouldn't really need to care for these and is why I
> hooked into the go command.

In this case you should use the common C API.

> I don't see much of a performance problem with a automatic full cache
> flush when using the go command on platforms with incoherent caches. In
> most use cases it's not very different from the bootm command which also
> needs to do the same (and using a similar hooking mechanism as what I
> used for go, but not saying that is a good thing)

No.  bootm  knows exactly the location and size of the image, so it is
sufficient to flush / invalidate a part of the memory, usually a
pretty small one compared to the total RAM size.

> And I do not think there needs to be commands for flushing specific
> regions other than for testing. Region based flushing is better done by
> code which knows what is needed. It's hard for users to get this right
> as most times it works anyway.

The code should know which ranges need flushing, not the user.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
"Now here's something you're really going to like!"
- Rocket J. Squirrel