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authorLinus Walleij <linus.walleij@linaro.org>2015-03-23 11:06:11 +0100
committerTom Rini <trini@konsulko.com>2015-03-28 12:07:45 -0400
commit202a674bb8b7d7867503224857a2b0e04617d9b3 (patch)
treeeb8cfaeb9ed0ce210212115c538323a255d53312 /doc
parente769f68613ee4f84c8e2aea784335df74ceea397 (diff)
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armv8: semihosting: add a command to load semihosted images
Instead of sprinkling custom code and calls over the Vexpress64 boardfile, create a command that loads images using semihosting just like we would load from flash memory of over the network, using a special command: smhload <image> <address> This will make it possible to remove some custom calls and code and make the boot easier. Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Diffstat (limited to 'doc')
-rw-r--r--doc/README.semihosting25
1 files changed, 5 insertions, 20 deletions
diff --git a/doc/README.semihosting b/doc/README.semihosting
index 7248560780..c016a4f840 100644
--- a/doc/README.semihosting
+++ b/doc/README.semihosting
@@ -30,25 +30,10 @@ vexpress_aemv8a.h but differentiate the two models by the presence or
absence of CONFIG_BASE_FVP. This change is tested and works on both the
Foundation and Base fastmodel simulators.
-The level of semihosting support is minimal, restricted to just what it
-takes to load images to memory. If more semihosting functionality is
-required, such as file seek, outputting strings, reading characters, etc,
-then it can be easily added later.
+The semihosting code adds a command:
-We require that the board include file define these env variables:
-- kernel_name e.g. "uImage"
-- kernel_addr_r e.g. "0x80000000"
-- initrd_name e.g. "ramdisk.img"
-- initrd_addr_r e.g. "0x88000000"
-- fdt_name e.g. "devtree.dtb"
-- fdt_addr_r e.g. "0x83000000"
+ smhload <image> <address> [env var]
-Optionally, "fdt_high" and "initrd_high" can be specified as per
-their rules for allowing or preventing copying of these images.
-
-For the "fdt chosen" startup macro, this code will then define:
-- initrd_end (based on retrieving initrd_addr_r plus actual initrd_size)
-
-We will then load the kernel, initrd, and fdt into the specified
-locations in memory in a similar way that the ATF fastmodel code
-uses semihosting calls to load other boot stages and u-boot itself.
+That will load an image from the host filesystem into RAM at the specified
+address and optionally store the load end address in the specified
+environment variable.
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