[PATCH 14/17] x86: coreboot: Document the memory map
Simon Glass
sjg at chromium.org
Wed Apr 7 06:32:24 CEST 2021
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 <sjg at chromium.org>
---
doc/board/coreboot/coreboot.rst | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/doc/board/coreboot/coreboot.rst b/doc/board/coreboot/coreboot.rst
index 9c44c025a48..e791b7e39f0 100644
--- a/doc/board/coreboot/coreboot.rst
+++ b/doc/board/coreboot/coreboot.rst
@@ -50,3 +50,22 @@ 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
+----------
+
+::
+
+ 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
--
2.31.0.208.g409f899ff0-goog
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