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authorShawn Guo <shawn.guo@linaro.org>2012-01-09 21:54:08 +0000
committerAlbert ARIBAUD <albert.u.boot@aribaud.net>2012-02-27 21:19:24 +0100
commitfa34f6b25b3c92f27b245c52378a0d2af24aaa19 (patch)
tree633f7e7a58730058e6b77e6800dcf41adc5e1bdb /README
parentba901df41b0d77088408c1f6aac65eaadd4d12a0 (diff)
common/image.c: align usage of fdt_high with initrd_high
The commit message of a28afca (Add uboot "fdt_high" enviroment variable) states that fdt_high behaves similarly to the existing initrd_high. But fdt_high actually has an outstanding difference from initrd_high. The former specifies the start address, while the later specifies the end address. As fdt_high and initrd_high will likely be used together, it'd be nice to have them behave same. The patch changes the behavior of fdt_high to have it aligned with initrd_high. The document of fdt_high in README is updated with an example to demonstrate the usage of this environment variable. Signed-off-by: Shawn Guo <shawn.guo@linaro.org> Acked-by: Simon Glass <sjg@chromium.org>
Diffstat (limited to 'README')
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1 files changed, 8 insertions, 0 deletions
diff --git a/README b/README
index eba63785368..89646725a0b 100644
--- a/README
+++ b/README
@@ -3665,6 +3665,14 @@ List of environment variables (most likely not complete):
fdt_high - if set this restricts the maximum address that the
flattened device tree will be copied into upon boot.
+ For example, if you have a system with 1 GB memory
+ at physical address 0x10000000, while Linux kernel
+ only recognizes the first 704 MB as low memory, you
+ may need to set fdt_high as 0x3C000000 to have the
+ device tree blob be copied to the maximum address
+ of the 704 MB low memory, so that Linux kernel can
+ access it during the boot procedure.
+
If this is set to the special value 0xFFFFFFFF then
the fdt will not be copied at all on boot. For this
to work it must reside in writable memory, have