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dm: spl: Support device tree when BSS is in a different section

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At present in SPL we place the device tree immediately after BSS. This
avoids needing to copy it out of the way before BSS can be used. However on
some boards BSS is not placed with the image - e.g. it can be in RAM if
available.

Add an option to tell U-Boot that the device tree should be placed at the
end of the image binary (_image_binary_end) instead of at the end of BSS.

Note: A common reason to place BSS in RAM is to support the FAT filesystem.
We should update the code so that it does not use so much BSS.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
This commit is contained in:
Simon Glass 2015-10-17 19:41:19 -06:00 committed by Michal Simek
parent 021b4d117c
commit 1017296247
3 changed files with 16 additions and 2 deletions
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10
Kconfig
View file

@ -152,6 +152,16 @@ config SPL_STACK_R_MALLOC_SIMPLE_LEN
to give board_init_r() a larger heap then the initial heap in
SRAM which is limited to SYS_MALLOC_F_LEN bytes.
config SPL_SEPARATE_BSS
depends on SPL
bool "BSS section is in a different memory region from text"
help
Some platforms need a large BSS region in SPL and can provide this
because RAM is already set up. In this case BSS can be moved to RAM.
This option should then be enabled so that the correct device tree
location is used. Normally we put the device tree at the end of BSS
but with this option enabled, it goes at _image_binary_end.
config TPL
bool
depends on SPL && SUPPORT_TPL

1
include/asm-generic/sections.h
View file

@ -71,6 +71,7 @@ extern char __bss_start[];
extern char __bss_end[];
extern char __image_copy_start[];
extern char __image_copy_end[];
extern char _image_binary_end[];
extern char __rel_dyn_start[];
extern char __rel_dyn_end[];

7
lib/fdtdec.c
View file

@ -1222,8 +1222,11 @@ int fdtdec_setup(void)
gd->fdt_blob = __dtb_dt_begin;
# elif defined CONFIG_OF_SEPARATE
# ifdef CONFIG_SPL_BUILD
/* FDT is at end of BSS */
gd->fdt_blob = (ulong *)&__bss_end;
/* FDT is at end of BSS unless it is in a different memory region */
if (IS_ENABLED(CONFIG_SPL_SEPARATE_BSS))
gd->fdt_blob = (ulong *)&_image_binary_end;
else
gd->fdt_blob = (ulong *)&__bss_end;
# else
/* FDT is at end of image */
gd->fdt_blob = (ulong *)&_end;