Since devices that can't DMA above 4GiB will misbehave with this option enabled add a warning on the documentation.
Reviewed-by: Simon Glass <[email protected]> Signed-off-by: Ilias Apalodimas <[email protected]> --- doc/develop/memory.rst | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/doc/develop/memory.rst b/doc/develop/memory.rst index 5177229630d1..3da39bb6c664 100644 --- a/doc/develop/memory.rst +++ b/doc/develop/memory.rst @@ -111,6 +111,15 @@ 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. + Boards can override thre relocation address via board_get_usable_ram_top(). + #. Code Relocation relocate_code() is called which relocates U-Boot code from the current -- 2.43.0
