On 03/20/2013 02:15:19 PM, Tom Rini wrote:
On Wed, Mar 20, 2013 at 11:43:15AM -0500, Scott Wood wrote:
> On 03/20/2013 09:58:36 AM, Wolfgang Denk wrote:
> >Dear Albert,
> >
> >In message <20130320145927.2031b913@lilith> you wrote:
> >>
> >> I do understand what it does, but I still don't get why it
should be
> >> done, since precisely payload control transfer happens through
> >bootm and
> >> the like which already properly flush cache.
>
> It doesn't always happen through bootm. Standalone apps use the
> "go" command.
So, to try and be a bit more verbose about this, for U-Boot
applications
which use 'go', we still need to ensure cache coherence, which is why
bootm does a cache flush, we need some way to flush in this case.
It's also an issue with using the "cpu <n> release" command.
And in this case you aren't better served by say bootelf ?
That wouldn't handle the "cpu release" case. In any case, "go" exists
and is currently the recommended way to launch a standalone application
in doc/README.standalone.
> It's a user command! How can it be dead code? I don't know of a
> way to include a human user in a patchset...
Can you hightlight what exactly causes the world today to go off and
fail? Is the hello_world example app sufficient in this case or do we
need something much larger?
A user inside Freescale is running standalone performance test apps,
using both "go" and "cpu <n> release" (since the test needs to run on
all CPUs). They are seeing cache problems running on a T4240 if they
don't have this flush. This flush is architecturally required between
modifying/loading code and running it.
-Scott
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