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author | Michael Clark <michaeljclark@mac.com> | 2018-05-21 13:29:31 +1200 |
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committer | Michael Clark <michaeljclark@mac.com> | 2018-05-22 21:41:18 +1200 |
commit | 474ee5a81880dcf60789e7c2a3054b3afb34c3ca (patch) | |
tree | 343a134219be59ee0347343a5ea415707d711ab3 /dummy_payload | |
parent | 9ffedde3d747a9b6f559041cc69478df6d647135 (diff) | |
download | pk-474ee5a81880dcf60789e7c2a3054b3afb34c3ca.zip pk-474ee5a81880dcf60789e7c2a3054b3afb34c3ca.tar.gz pk-474ee5a81880dcf60789e7c2a3054b3afb34c3ca.tar.bz2 |
RISC-V: Support separate firmware and kernel payload
Support for separate firmware and kernel payload is added
by updating BBL to read optional preloaded kernel address
attributes from device-tree using a similar mechanism to
that used to pass init ramdisk addresses to linux kernel.
chosen {
riscv,kernel-start = <0x00000000 0x80200000>;
riscv,kernel-end = <0x00000000 0x80590634>;
};
These attributes are added by QEMU and read by BBL when combining
-bios <firmware-image> and -kernel <kernel-image> options. e.g.
$ qemu-system-riscv64 -machine virt -bios bbl -kernel vmlinux
With this change, bbl can be compiled without --with-payload
and the dummy payload alignment is altered to make the memory
footprint of the firmware-only bbl smaller. The dummy payload
message is updated to indicate the alternative load method.
This load method could also be supported by a first stage boot
loader that reads seperate firmware and kernel from SPI flash.
The main advantage of this new mechanism is that it eases kernel
development by avoiding the riscv-pk packaging step after kernel
builds, makes building per repository artefacts for CI simpler,
and mimics bootloaders on other platforms that can load a kernel
image file directly. Ultimately BBL should use an SPI driver to
load the kernel image however this mechanism supports use cases
such such as QEMU's -bios, -kernel and -initrd options following
examples from other platforms that pass kernel entry to firmware
via device-tree.
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Alistair Francis <Alistair.Francis@wdc.com>
Signed-off-by: Michael Clark <mjc@sifive.com>
Diffstat (limited to 'dummy_payload')
-rw-r--r-- | dummy_payload/dummy_entry.S | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/dummy_payload/dummy_entry.S b/dummy_payload/dummy_entry.S index 92d4652..2473d8c 100644 --- a/dummy_payload/dummy_entry.S +++ b/dummy_payload/dummy_entry.S @@ -18,5 +18,11 @@ _start: .data str: - .asciz "This is bbl's dummy_payload. To boot a real kernel, reconfigure\n\ -bbl with the flag --with-payload=PATH, then rebuild bbl.\n" + .asciz "This is bbl's dummy_payload. To boot a real kernel, reconfigure bbl +with the flag --with-payload=PATH, then rebuild bbl. Alternatively, +bbl can be used in firmware-only mode by adding device-tree nodes +for an external payload and use QEMU's -bios and -kernel options.\n + chosen { + riscv,kernel-start = <payload_start>; + riscv,kernel-end = <payload_end>; + };\n\n" |