Nios II 中的缓存和内存数据的读写
nios 使用地址中31bit来表示访问是否bypass cache。
如果bit 31=0 表示不bypass cache,即使用cache里的数据;如果bit 31=1表示bypass cache,即直接使用mem中的数据。
如alt_remap_uncached函数
1 #ifdef NIOS2_MMU_PRESENT 2 /* Convert KERNEL region address to IO region address */ 3 #define BYPASS_DCACHE_MASK (0x1 << 29) 4 #else 5 /* Set bit 31 of address to bypass D-cache */ 6 #define BYPASS_DCACHE_MASK (0x1 << 31) 7 #endif 8 9 /* 10 * Convert a pointer to a block of cached memory, into a block of 11 * uncached memory. 12 */ 13 14 volatile void* alt_remap_uncached (void* ptr, alt_u32 len) 15 { 16 alt_dcache_flush (ptr, len); 17 return (volatile void*) (((alt_u32) ptr) | BYPASS_DCACHE_MASK); 18 }
其中
1 #ifdef NIOS2_FLUSHDA_SUPPORTED 2 #define ALT_FLUSH_DATA(i) __asm__ volatile ("flushda (%0)" :: "r" (i)); 3 #else 4 #define ALT_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 memory 9 * region of length "len" bytes, starting at address "start". 10 * 11 * Any dirty lines in the data cache are written back to memory. 12 */ 13 14 void alt_dcache_flush (void* start, alt_u32 len) 15 { 16 #if NIOS2_DCACHE_SIZE > 0 17 18 char* i; 19 char* end; 20 21 /* 22 * This is the most we would ever need to flush. 23 * 24 * SPR 196942, 2006.01.13: The cache flush loop below will use the 25 * ‘flushda‘ instruction if its available; in that case each line 26 * must be flushed individually, and thus ‘len‘ cannot be trimmed. 27 */ 28 #ifndef NIOS2_FLUSHDA_SUPPORTED 29 if (len > NIOS2_DCACHE_SIZE) 30 { 31 len = NIOS2_DCACHE_SIZE; 32 } 33 #endif 34 35 end = ((char*) start) + len; 36 37 for (i = start; i < end; i+= NIOS2_DCACHE_LINE_SIZE) 38 { 39 ALT_FLUSH_DATA(i); 40 } 41 42 /* 43 * For an unaligned flush request, we‘ve got one more line left. 44 * Note that this is dependent on NIOS2_DCACHE_LINE_SIZE to be a 45 * multiple of 2 (which it always is). 46 */ 47 48 if (((alt_u32) start) & (NIOS2_DCACHE_LINE_SIZE - 1)) 49 { 50 ALT_FLUSH_DATA(i); 51 } 52 53 #endif /* NIOS2_DCACHE_SIZE > 0 */ 54 }
郑重声明:本站内容如果来自互联网及其他传播媒体,其版权均属原媒体及文章作者所有。转载目的在于传递更多信息及用于网络分享,并不代表本站赞同其观点和对其真实性负责,也不构成任何其他建议。