From e74d0ec80bfd4a8326008836dfc81099382a41b5 Mon Sep 17 00:00:00 2001 From: Simon Glass Date: Sun, 27 Jun 2021 17:51:08 -0600 Subject: [PATCH] x86: coreboot: Document the memory map Add information about memory usage when U-Boot is started from coreboot. This is useful when debugging. Also, since coreboot takes a chunk of memory in the middle of SDRAM for use by PCI devices, it can help avoid overwriting this with a loaded kernel by accident. Signed-off-by: Simon Glass Reviewed-by: Bin Meng --- doc/board/coreboot/coreboot.rst | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/doc/board/coreboot/coreboot.rst b/doc/board/coreboot/coreboot.rst index 9c44c025a4..3792f9e1c8 100644 --- a/doc/board/coreboot/coreboot.rst +++ b/doc/board/coreboot/coreboot.rst @@ -50,3 +50,24 @@ works by using a 32-bit SPL binary to switch to 64-bit for running U-Boot. It can be useful for running UEFI applications, for example. This has only been lightly tested. + + +Memory map +---------- + + ========== ================================================================== + Address Region at that address + ========== ================================================================== + ffffffff Top of ROM (and last byte of 32-bit address space) + 7a9fd000 Typical top of memory available to U-Boot + (use cbsysinfo to see where memory range 'table' starts) + 10000000 Memory reserved by coreboot for mapping PCI devices + (typical size 2151000, includes framebuffer) + 1920000 CONFIG_SYS_CAR_ADDR, fake Cache-as-RAM memory, used during startup + 1110000 CONFIG_SYS_TEXT_BASE (start address of U-Boot code, before reloc) + 110000 CONFIG_BLOBLIST_ADDR (before being relocated) + 100000 CONFIG_PRE_CON_BUF_ADDR + f0000 ACPI tables set up by U-Boot + (typically redirects to 7ab10030 or similar) + 500 Location of coreboot sysinfo table, used during startup + ========== ================================================================== -- 2.39.5