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Altera_Forum
Honored Contributor I
840 Views

Nios f / Custom MM Slave

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.
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2 Replies
Altera_Forum
Honored Contributor I
21 Views

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
Honored Contributor I
21 Views

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)