[PATCH v4 6/6] doc: Add a warning about using RELOC_ADDR_TOP

[Ilias Apalodimas]

Since devices that can't DMA above 4GiB will misbehave with this option
enabled add a warning on the documentation.

Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
---
 doc/develop/memory.rst | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/doc/develop/memory.rst b/doc/develop/memory.rst
index 5177229630d1..ffee06c1530c 100644
--- a/doc/develop/memory.rst
+++ b/doc/develop/memory.rst
@@ -110,6 +110,12 @@ U-Boot Proper Flow
 
       This follows the same as in SPL flow. In board_init_f(), a part of memory
       is reserved at the end of RAM (see reserve_* functions in init_sequence_f)
+   #. Relocation address
+      By default U-Boot will try to relocate below the 4GiB boundary. If
+      RELOC_ADDR_TOP is enabled U-Boot will look into the dram bank config of
+      gd->dram[] and try to relocate to the highest available bank. Use this
+      with caution as devices that can only DMA below 4GiB will misbehave
+      since their buffers may be allocated above the 32-bit boundary.
 
    #. Code Relocation
 
-- 
2.53.0