u-boot/doc/README.arm-caches

1 Disabling I-cache:
2 - Set CONFIG_SYS_ICACHE_OFF
4 Disabling D-cache:
5 - Set CONFIG_SYS_DCACHE_OFF
7 Enabling I-cache:
8 - Make sure CONFIG_SYS_ICACHE_OFF is not set and call icache_enable().
10 Enabling D-cache:
11 - Make sure CONFIG_SYS_DCACHE_OFF is not set and call dcache_enable().
14 - Implement enable_caches() for your platform and enable the I-cache and
15   D-cache from this function. This function is called immediately
18 Guidelines for Working with D-cache:
21 - Flush the buffer after the MPU writes the data and before the DMA is
25 - Invalidate the buffer before starting the DMA. In case there are any dirty
26   lines from the DMA buffer in the cache, subsequent cache-line replacements
27   may corrupt the buffer in memory while the DMA is still going on. Cache-line
29   into the cache while the DMA is going on.
30 - Invalidate the buffer after the DMA is complete and before the MPU reads
33   come to the cache due to speculative memory access by the CPU. If this
37 - Any buffer that is invalidated(that is, typically the peripheral to
38   memory DMA buffer) should be aligned to cache-line boundary both at
40 - If the buffer is not cache-line aligned invalidation will be restricted
41   to the aligned part. That is, one cache-line at the respective boundary
43 - A suitable buffer can be alloced on the stack using the
47 - cleanup_before_linux() should flush the D-cache, invalidate I-cache, and
49 - The following sequence is advisable while disabling d-cache:
50   1. dcache_disable() - flushes and disables d-cache
51   2. invalidate_dcache_all() - invalid any entry that came to the cache
52 	in the short period after the cache was flushed but before the
53 	cache got disabled.