PowerPC Cache Warning Help Request

[Joel Sherrill]

On October 20, 2014 3:41:06 PM CDT, Peter Dufault <dufault at hda.com> wrote:
>
>> On Oct 20, 2014, at 13:20 , Joel Sherrill <Joel.Sherrill at oarcorp.com>
>wrote:
>> 
>> 
>> On 10/20/2014 12:09 PM, Gedare Bloom wrote:
>>> Cache manager implementations are a perennial open project.
>> +1
>> 
>> In this case,we only have ten RTEMS_CPU_MODELs which are not
>> addressed.  There are currently two blocks of code in the file. One
>> is protected by this:
>> 
>> #if defined(ppc603) || defined(ppc603e) || defined(mpc8260)
>> 
>> And the other by this:
>> 
>> #elif ( defined(mpx8xx) || defined(mpc860) || defined(mpc821) )
>> 
>> My guess with no research is that the first block of code is also
>> appropriate for these RTEMS_CPU_MODELs:
>> 
>> e500
>> mpc604
>> mpc7400 mpc7455 mpc750
>> qoriq
>> mpc55xx
>> 
>> A quick google makes me pretty confident that the mpc690 and mpc7*
>models
>> belong in the ppc603 HID0 block.
>> 
>> I do not have a guess about these
>> 
>> ppc405 ppc440 mpc555
>> 
>> If we have to implement code to support something new, then I don't
>want
>> to do it. If we have the code and just need to check to see if more
>needs to
>> be added to the conditional, then we should.
>> 
>> --joel
>> 
>
>I'm not sure.  I looked at this briefly today.  The MPC55XX has a
>unified cache, a lot of the unimplemented entry points had to to do
>with operations specifically on either the instruction or data cache. 
>I agree you could implement a unified method where accessing either
>would affect the other, but I also agree with Sebastian that I'm not
>sure it matters if someone is trying to use one of those for good
>reason.
>
>However, should unimplemented versions return an error instead of being
>a NOP?  That would force one to visit code that makes assumptions.

If this is OK for the mpc55xx, feel free to submit a patch turning the warning off for it.

I tend to agree that if I had a generic drive that wanted to flush data cache and all we can do on a target is flush all, then that's preferable to flushing nothing.

If these are called from a cache test then we would end up with a hard error instead of a warning in that test which makes the issue worse. 


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