X-Git-Url: https://git.sur5r.net/?a=blobdiff_plain;f=README;h=604f0fa78e5141839e29e8d855a2932f537b3f69;hb=fc0f25f91948eef623999ab0874d6bd4604cb889;hp=42ece994739cd4f56f39e32861d57c78503bc3bc;hpb=7a7ffedabd29adde9cb6ebe6066256c4cf8b77af;p=u-boot

diff --git a/README b/README
index 42ece99473..604f0fa78e 100644
--- a/README
+++ b/README
@@ -4016,6 +4016,25 @@ Configuration Settings:
 		boards which do not use the full malloc in SPL (which is
 		enabled with CONFIG_SYS_SPL_MALLOC_START).
 
+- CONFIG_SYS_NONCACHED_MEMORY:
+		Size of non-cached memory area. This area of memory will be
+		typically located right below the malloc() area and mapped
+		uncached in the MMU. This is useful for drivers that would
+		otherwise require a lot of explicit cache maintenance. For
+		some drivers it's also impossible to properly maintain the
+		cache. For example if the regions that need to be flushed
+		are not a multiple of the cache-line size, *and* padding
+		cannot be allocated between the regions to align them (i.e.
+		if the HW requires a contiguous array of regions, and the
+		size of each region is not cache-aligned), then a flush of
+		one region may result in overwriting data that hardware has
+		written to another region in the same cache-line. This can
+		happen for example in network drivers where descriptors for
+		buffers are typically smaller than the CPU cache-line (e.g.
+		16 bytes vs. 32 or 64 bytes).
+
+		Non-cached memory is only supported on 32-bit ARM at present.
+
 - CONFIG_SYS_BOOTM_LEN:
 		Normally compressed uImages are limited to an
 		uncompressed size of 8 MBytes. If this is not enough,