Nios f / Custom MM Slave

Altera_Forum · ‎04-26-2014

Hi all,

I know this has been asked several times on the forum but I must be missing the point as I'm still at encountering the issue. I have tested my SoPC fine with the nios e.

The problems occur when using the nios f. I have the data and instruction caches set to 4kb's, and after a bit of reading(and testing) I know I need to bypass my data cache to successfully test my system with my custom MM slave. The address of my MM slave in Qsys is 00081_1100 - 0x0081_117f.

In my header file avs.h, the base address matches that of system.h(and Qsys of course)

#define avs_base 0x811_1100

As I'm using HAL, I know there are 3 methods to bypass the cache:

1. Bypass by using IORD and IOWR.

2. Set bit 31

3. Use alt_remap_uncached()

As I have my program written, I was hoping to implement# 3 in my avs.c file by the following method:

# include "aes.h"# include <stdio.h># include <sys/alt_cache.h>
........................# define avsrange 177
int main{
// insert alt_remap_uncached
.......
}

Would I be correct so far, and in saying this would be the most straightforward method to implement?

I have reviewed the documentation but it's not becoming any clearer in my mind.

Going by this document (http://www.altera.com/literature/hb/nios2/n2sw_nii52010.pdf) the function is defined as

volatile void* alt_remap_uncached (void* ptr, 
alt_u32 len);

where 'ptr' is starting address and 'len' is the memory range.

So, would this translate, in my example, to:

alt_remap_uncached((void*)AVS_BASE, avsrange);

Edit: I know the last piece of code does not work. Also, I am not using the nios MMU so perhaps option 2 is workable.

Altera_Forum · ‎04-27-2014

alt_remap_uncached() simply returns a new pointer with bit 31 set. Your code fragment doesn't show you are doing anything with the return value, so perhaps this is the piece you are missing?

e.g.


alt_u32 *my_block = alt_remap_uncached( AVS_BASE, avsrange );
my_block = foo;

Altera_Forum · ‎04-27-2014

Thanks, I resolved this by ANDing my custom components base address with 0x8000_0000 to set MSB to 1. Still having issues but data is no longer cached.

I'm debugging at the moment so I think this resolved the caching issue.

In the header file, avs.h:

#define AVS_BASEADDR (0x811100 | 0x80000000)