diff options
| -rw-r--r-- | arch/arm/lib/board.c | 8 | ||||
| -rw-r--r-- | arch/arm/lib/cache.c | 12 | ||||
| -rw-r--r-- | doc/README.arm-caches | 51 | ||||
| -rw-r--r-- | include/common.h | 1 |
4 files changed, 67 insertions, 5 deletions
diff --git a/arch/arm/lib/board.c b/arch/arm/lib/board.c index c899839..a7fb251 100644 --- a/arch/arm/lib/board.c +++ b/arch/arm/lib/board.c @@ -452,11 +452,9 @@ void board_init_r(gd_t *id, ulong dest_addr) gd->flags |= GD_FLG_RELOC; /* tell others: relocation done */ monitor_flash_len = _end_ofs; - /* - * Enable D$: - * I$, if needed, must be already enabled in start.S - */ - dcache_enable(); + + /* Enable caches */ + enable_caches(); debug("monitor flash len: %08lX\n", monitor_flash_len); board_init(); /* Setup chipselects */ diff --git a/arch/arm/lib/cache.c b/arch/arm/lib/cache.c index 92b61a2..b545fb7 100644 --- a/arch/arm/lib/cache.c +++ b/arch/arm/lib/cache.c @@ -53,3 +53,15 @@ void __flush_dcache_all(void) } void flush_dcache_all(void) __attribute__((weak, alias("__flush_dcache_all"))); + + +/* + * Default implementation of enable_caches() + * Real implementation should be in platform code + */ +void __enable_caches(void) +{ + puts("WARNING: Caches not enabled\n"); +} +void enable_caches(void) + __attribute__((weak, alias("__enable_caches"))); diff --git a/doc/README.arm-caches b/doc/README.arm-caches new file mode 100644 index 0000000..cd2b458 --- /dev/null +++ b/doc/README.arm-caches @@ -0,0 +1,51 @@ +Disabling I-cache: +- Set CONFIG_SYS_ICACHE_OFF + +Disabling D-cache: +- Set CONFIG_SYS_DCACHE_OFF + +Enabling I-cache: +- Make sure CONFIG_SYS_ICACHE_OFF is not set and call icache_enable(). + +Enabling D-cache: +- Make sure CONFIG_SYS_DCACHE_OFF is not set and call dcache_enable(). + +Enabling Caches at System Startup: +- Implement enable_caches() for your platform and enable the I-cache and + D-cache from this function. This function is called immediately + after relocation. + +Guidelines for Working with D-cache: + +Memory to Peripheral DMA: +- Flush the buffer after the MPU writes the data and before the DMA is + initiated. + +Peripheral to Memory DMA: +- Invalidate the buffer before starting the DMA. In case there are any dirty + lines from the DMA buffer in the cache, subsequent cache-line replacements + may corrupt the buffer in memory while the DMA is still going on. Cache-line + replacement can happen if the CPU tries to bring some other memory locations + into the cache while the DMA is going on. +- Invalidate the buffer after the DMA is complete and before the MPU reads + it. This may be needed in addition to the invalidation before the DMA + mentioned above, because in some processors memory contents can spontaneously + come to the cache due to speculative memory access by the CPU. If this + happens with the DMA buffer while DMA is going on we have a coherency problem. + +Buffer Requirements: +- Any buffer that is invalidated(that is, typically the peripheral to + memory DMA buffer) should be aligned to cache-line boundary both at + at the beginning and at the end of the buffer. +- If the buffer is not cache-line aligned invalidation will be restricted + to the aligned part. That is, one cache-line at the respective boundary + may be left out while doing invalidation. + +Cleanup Before Linux: +- cleanup_before_linux() should flush the D-cache, invalidate I-cache, and + disable MMU and caches. +- The following sequence is advisable while disabling d-cache: + 1. disable_dcache() - flushes and disables d-cache + 2. invalidate_dcache_all() - invalid any entry that came to the cache + in the short period after the cache was flushed but before the + cache got disabled. diff --git a/include/common.h b/include/common.h index 12a1074..bd10f31 100644 --- a/include/common.h +++ b/include/common.h @@ -616,6 +616,7 @@ ulong lcd_setmem (ulong); ulong video_setmem (ulong); /* arch/$(ARCH)/lib/cache.c */ +void enable_caches(void); void flush_cache (unsigned long, unsigned long); void flush_dcache_all(void); void flush_dcache_range(unsigned long start, unsigned long stop); |