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

[Wolfgang Denk]

Dear Henrik Nordström,

In message <1368669278.27007.43.camel at localhost> you wrote:
> 
> > So my suggestion is to implement the icache_flush in common/bmmt_cmd.c
> > as follows:
...
> From what I can tell there is no need to theck icache_status(). It's
> always safe to call invalidate_icache_all().
> 
> So it's back to use the compiler define for ARMv7.

I don't think this would be an acceptable approach.  There are several
serious issues with the suggested patch.


First, I think your solution in not complete.   Invalidating the
instruction cache is only one part of what needs to be done.  You
should also make sure to flush the data cache.

Second, flushing _all_ caches may be a time consuming operation on
some systems, and it is not necessary.  It should be sufficient to
flush the address range where the loaded code resides.

Third, Albert is perfectly right:  there is no reason to make this
architecture specific.  We should NOT add such code here and there on
a per-arch base; this results only in code fragmentation, duplication
and a maintenance nightmare.

Finally, a very similar topic has been discussed here not so long ago;
please see the thread "command/cache: Add flush command" at [1], [2],
and [3]; see especially the attempt of a summary at [4].

[1] http://thread.gmane.org/gmane.comp.boot-loaders.u-boot/156449
[2] http://thread.gmane.org/gmane.comp.boot-loaders.u-boot/158038
[3] http://thread.gmane.org/gmane.comp.boot-loaders.u-boot/158101

[4] http://thread.gmane.org/gmane.comp.boot-loaders.u-boot/158101/focus=158559


In the summary I tried to explain what I think we should do to strive
for more common code; unfortunately did not follow this suggestion but
decided to keep his code out-of-tree.  But I still think this is what
should be done, also in your case.

We should not add architecture-specific code like you suggested.

Best regards,

Wolfgang Denk

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