Doubts About Cache Manager Routines

[Thomas Doerfler (nt)]

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Naufal,

maybe using a local (stack) variable as a test target is not really a
good idea, because you will _always_ hit stuff in the neighbourhood.
Your analysis is totally to the point regarding the effects you have.

A proper way may include:
- - allocate a cache-aligned chunk of memory (e.g. from the heap, using
malloc() ).
- - use this location as your test area.

wkr,
Thomas.


Am 05.04.2011 20:49, schrieb Mohamed Naufal:
> Hi
> 
> I'm trying to implement to write an sptest to check the working of
> cache manager routines as a qualification task for the cache manager
> support GSoC project.
> 
> This is what I have so far:
> 
> on i386:
> 
> rtems_task Init(rtems_task_argument arg)
> {
>    int volatile a = 1;
>    //Writeback and invalidate
>    __asm__ __volatile__("wbinvd");
>    a = 2;
>    //Invalidate
>    __asm__ __volatile__("invd");
>    if (a == 1)
>        printf("Invalidation successful\n");
>    else
>        printf("Invalidation unsuccessful\n");
> 
>    exit(0);
> }
> This doesn't work on qemu but does on real hardware.
> 
> Using the cache manager routines, this is what I did
> rtems_task Init(rtems_task_argument arg)
> {
>    int volatile a = 1;
> 
>    rtems_cache_data_enable();
>    rtems_cache_flush_entire_data();
>    a = 2;
>    rtems_cache_invalidate_entire_data();
>    if (a == 1)
>        printf("Invalidation successful\n");
>    else
>        printf("Invalidation unsuccessful\n");
> 
>    exit(0);
> }
> 
> This doesn't work as I'd hoped. On checking, it seems
> invalidate_data() returns to the line a=2 and thus infinite loops.My
> understanding is that in the invalidate function, the dirty blocks
> including the stack part which contains the return address are
> invalidated. So it uses the return address of the flush function which
> was the previously written out to the same memory location.
> 
> How do I handle this?
> 
> Thanks
> Naufal
> _______________________________________________
> rtems-users mailing list
> rtems-users at rtems.org
> http://www.rtems.org/mailman/listinfo/rtems-users


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IMD Ingenieurbuero fuer Microcomputertechnik
Thomas Doerfler           Herbststrasse 8
D-82178 Puchheim          Germany
email:    Thomas.Doerfler at imd-systems.de
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