PowerPC Cache Warning Help Request

[Peter Dufault]

> On Oct 23, 2014, at 09:38 , Sebastian Huber <sebastian.huber at embedded-brains.de> wrote:
> 
>>> What do you mean with "return errors"?  Should this be a fatal error or
>>> a
>>> linker error?
>> 
>> Let's take the simplest case. A CPU with no cache control. Empty stubs is the right implementation.
>> 
>> Next up is just enable, disable and flush. Can we map those to more specialized methods. Is it ok and expected that disable data cache does all? Or flush flushes all.
> 
> What is the use case for a cache disable/enable at application level?  Most 
> cache disable functions in the tree are broken.
> 
> The only useful cache manager functions I see is data cache flush/invalidate 
> lines and instruction cache invalidate lines.
> 
> 

My original thinking about "return errors" is to return an error code when an unimplemented function is called, because somebody called that function for what they thought was a good reason.  A link-time warning (not error) if the function is linked-in to the user application would be great, I don't know if that is possible.  That approach moves the warning from the BSP compilation stage to the conscious usage of an unusual unimplemented function by a BSP user.

I don't know what the use cases of all those cache manager functions are.  The few real-world unusual cache usages that I can think of are chip and application specific (e.g. reserve a section of cache as a section to store some critical code in) and I wouldn't even attempt to generalize them for use in a "manager".

My desirements would be, in order and if possible:
- Link time warning when an unimplemented function is called from an application;
- Run-time error return (not fatal abort type thing, but something the application should handle) when an unimplemented function is called;
- Nothing at all.

Peter
-----------------
Peter Dufault
HD Associates, Inc.      Software and System Engineering