sandbox: Add un/map_sysmen() to deal with sandbox's ram_buf

[people/ms/u-boot.git] / README

diff --git a/README b/README
index 0070694438c956cad17af9ce27149cc7f98041c0..51eb71b27c5de9015bd7676f79930b6c16fb2a75 100644 (file)
--- a/README
+++ b/README
@@ -3811,6 +3811,15 @@ Low Level (hardware related) configuration options:
                that is executed before the actual U-Boot. E.g. when
                compiling a NAND SPL.
 
+- CONFIG_ARCH_MAP_SYSMEM
+               Generally U-Boot (and in particular the md command) uses
+               effective address. It is therefore not necessary to regard
+               U-Boot address as virtual addresses that need to be translated
+               to physical addresses. However, sandbox requires this, since
+               it maintains its own little RAM buffer which contains all
+               addressable memory. This option causes some memory accesses
+               to be mapped through map_sysmem() / unmap_sysmem().
+
 - CONFIG_USE_ARCH_MEMCPY
   CONFIG_USE_ARCH_MEMSET
                If these options are used a optimized version of memcpy/memset will