path: root/README
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authorYork Sun <>2015-12-04 11:57:07 -0800
committerYork Sun <>2015-12-15 08:57:32 +0800
commite81495224f732f17ae6f379baf23b90cd1d5cb5f (patch)
treef0e798cad86d64d6c2978307c94299f7f30eb208 /README
parent000f4e7686f4291fbd74d8920b586caf10f9241f (diff)
Reserve secure memory
Secure memory is at the end of memory, separated and reserved from OS, tracked by gd->secure_ram. Secure memory can host MMU tables, security monitor, etc. This is different from PRAM used to reserve private memory. PRAM offers memory at the top of u-boot memory, not necessarily the real end of memory for systems with very large DDR. Using the end of memory simplifies MMU setup and avoid memory fragmentation. "bdinfo" command shows gd->secure_ram value if this memory is marked as secured. Signed-off-by: York Sun <>
Diffstat (limited to 'README')
1 files changed, 8 insertions, 0 deletions
diff --git a/README b/README
index 4fee7066d5..6ea1af2678 100644
--- a/README
+++ b/README
@@ -3869,6 +3869,14 @@ Configuration Settings:
Scratch address used by the alternate memory test
You only need to set this if address zero isn't writeable
+ If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
+ is substracted from total RAM and won't be reported to OS.
+ This memory can be used as secure memory. A variable
+ gd->secure_ram is used to track the location. In systems
+ the RAM base is not zero, or RAM is divided into banks,
+ this variable needs to be recalcuated to get the address.
If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
this specified memory area will get subtracted from the top
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