binman: tegra: Adjust symbol calculation depending on end-at-4gb

A recent change adjusted the symbol calculation to work on x86 but broke
it for Tegra. In fact this is because they have different needs.

On x86 devices the code is linked to a ROM address and the end-at-4gb
property is used for the image. In this case there is no need to add the
base address of the image, since the base address is already built into
the offset and image-pos properties.

On other devices we must add the base address since the offsets start at
zero.

In addition the base address is currently added to the 'offset' and 'size'
values. It should in fact only be added to 'image-pos', since 'offset' is
relative to its parent and 'size' is not actually an address. This code
should have been adjusted when support for 'image-pos' and 'size' was
added, but it was not.

To correct these problems:
- move the code that handles adding the base address to section.py, which
  can check the end-at-4gb property and which property
  (offset/size/image-pos) is being read
- add the base address only when needed (only for image-pos and not if the
  image uses end-at-4gb)
- add a note to the documentation
- add a separate test to cover x86 behaviour

Fixes: 15c981cc (binman: Correct symbol calculation with non-zero image base)

Signed-off-by: Simon Glass <sjg@chromium.org>
Tested-by: Stephen Warren <swarren@nvidia.com>

1 files changed, 26 insertions, 8 deletions

diff --git a/tools/binman/README b/tools/binman/README
index c96a5642267..20a80944e29 100644
--- a/tools/binman/README
+++ b/tools/binman/README
@@ -766,20 +766,38 @@ when SPL is finished.
 Binman allows you to declare symbols in the SPL image which are filled in
 with their correct values during the build. For example:
 
-    binman_sym_declare(ulong, u_boot_any, offset);
+    binman_sym_declare(ulong, u_boot_any, image_pos);
 
-declares a ulong value which will be assigned to the offset of any U-Boot
+declares a ulong value which will be assigned to the image-pos of any U-Boot
 image (u-boot.bin, u-boot.img, u-boot-nodtb.bin) that is present in the image.
 You can access this value with something like:
 
-    ulong u_boot_offset = binman_sym(ulong, u_boot_any, offset);
+    ulong u_boot_offset = binman_sym(ulong, u_boot_any, image_pos);
 
-Thus u_boot_offset will be set to the offset of U-Boot in memory, assuming that
-the whole image has been loaded, or is available in flash. You can then jump to
-that address to start U-Boot.
+Thus u_boot_offset will be set to the image-pos of U-Boot in memory, assuming
+that the whole image has been loaded, or is available in flash. You can then
+jump to that address to start U-Boot.
 
-At present this feature is only supported in SPL. In principle it is possible
-to fill in such symbols in U-Boot proper, as well.
+At present this feature is only supported in SPL and TPL. In principle it is
+possible to fill in such symbols in U-Boot proper, as well, but a future C
+library is planned for this instead, to read from the device tree.
+
+As well as image-pos, it is possible to read the size of an entry and its
+offset (which is the start position of the entry within its parent).
+
+A small technical note: Binman automatically adds the base address of the image
+(i.e. __image_copy_start) to the value of the image-pos symbol, so that when the
+image is loaded to its linked address, the value will be correct and actually
+point into the image.
+
+For example, say SPL is at the start of the image and linked to start at address
+80108000. If U-Boot's image-pos is 0x8000 then binman will write an image-pos
+for U-Boot of 80110000 into the SPL binary, since it assumes the image is loaded
+to 80108000, with SPL at 80108000 and U-Boot at 80110000.
+
+For x86 devices (with the end-at-4gb property) this base address is not added
+since it is assumed that images are XIP and the offsets already include the
+address.
 
 
 Access to binman entry offsets at run time (fdt)