Reading and writing of cache and memory data in Nios II

Nios uses 31bit in the address to indicate whether the access is bypass cache.
If bit 31=0 indicates that the cache is not bypass, it uses the data in the cache, and if bit 31=1 represents the bypass cache, the data in the mem is used directly.
such as the alt_remap_uncached function

1 #ifdef nios2_mmu_present2 /*Convert KERNEL Region address to IO region address*/3 #defineBypass_dcache_mask (0x1 << 29)4 #else5 /*Set bit of address to bypass D-cache*/6 #defineBypass_dcache_mask (0x1 << 31)7 #endif8 9 /*Ten * Convert A pointer to a block of cached memory, into a block of One * uncached memory. A  */ -  - volatile void* Alt_remap_uncached (void*ptr, alt_u32 len) the { - Alt_dcache_flush (PTR, Len); -   return(volatile void*) (((ALT_U32) ptr) |bypass_dcache_mask); -}

which

1 #ifdef nios2_flushda_supported2 #defineAlt_flush_data (i) __asm__ volatile ("Flushda (%0)":: "R" (i));3 #else4 #defineAlt_flush_data (i) __asm__ volatile ("flushd (%0)":: "R" (i));5 #endif/* nios2_flushda_supported */6 7 /*8 * Alt_dcache_flush () is called to flush the data cache for a memory9 * Region of the length "Len" bytes, starting at address "start".Ten  * One * Any dirty lines in the data cache is written back to memory. A  */ -  - voidAlt_dcache_flush (void*start, alt_u32 len) the { - #ifNios2_dcache_size > 0 -  -   Char*i; +   Char*end; -  +   /* A * This is the most of we would ever need to flush. at    * - * SPR 196942, 2006.01.13:the cache flush loop below 'll use the - * ' flushda ' instruction if its available; - * must is flushed individually, and thus ' Len ' cannot be trimmed. -    */ - #ifndef nios2_flushda_supported in   if(Len >nios2_dcache_size) -   { toLen =nios2_dcache_size; +   } -   #endif the  *End = ((Char*) Start) +Len; $ Panax Notoginseng    for(i = start; i < end; i+=nios2_dcache_line_size) -   {  the Alt_flush_data (i); +   } A  the   /*  + * For a unaligned flush request, we ' ve got one more line left. - * Note that this was dependent on nios2_dcache_line_size to be a $ * Multiple of 2 (which it always is). $    */ -  -   if((ALT_U32) Start) & (Nios2_dcache_line_size-1)) the   { - Alt_flush_data (i);Wuyi   } the  - #endif/* nios2_dcache_size > 0 */ Wu}

Reading and writing of cache and memory data in Nios II