Wire up the flags word and the three override values in the OpenSBI
firmware header. When the previous booting stage sets one of the
FW_HEADER_FLAGS_OVERRIDE_A[012] bits, the cold boot path replaces the
matching register with the value stored in the header before doing
anything else with the boot arguments.
This lets a previous booting stage which cannot pass the boot arguments
in registers hand them over by patching a few words in the firmware
image instead. For example, a booting stage running on a dedicated boot
processor can load the OpenSBI image, patch the header with the hart id,
the DTB address and, for FW_DYNAMIC, the address of a struct
fw_dynamic_info it built somewhere in DRAM, and then release the hart
that runs OpenSBI, without ever being able to set up that hart's
registers itself.
The flags word is zero in a freshly built image, so nothing is
overridden and every existing booting stage keeps passing a0, a1 and a2
in registers as before.
Suggested-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Zong Li <zong.li@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20260918081313.659655-3-zong.li@sifive.com
Signed-off-by: Anup Patel <anup@brainfault.org>
Add a fixed 128-byte header at the very beginning of every OpenSBI
firmware image, regardless of the firmware type. The header lets the
previous booting stage identify an OpenSBI image and, more importantly,
gives it a well-known place inside the image to hand over information
to OpenSBI by patching a few words instead of setting up registers.
This first patch only introduces the layout:
- a 4-byte jump over the header to _start_real, so that _start stays
the entry point of the image. The jump is assembled with
'.option norvc' so that the fields behind it are always at a fixed
offset, even for a build with compressed instructions enabled,
- the 'OSBI' magic, a header version, the XLEN the firmware was built
for and the size of the firmware image, so that the previous booting
stage can validate the image and figure out how much memory it
occupies,
- a flags word and three 8-byte override values, which are unused
(and zero) for now and are wired up by the next patch.
The layout is deliberately identical for RV32 and RV64 so that the
previous booting stage can parse the header without knowing the XLEN of
the firmware upfront. Each override value is followed by a reserved
8-byte slot so that the same layout can be extended to RV128 later.
Suggested-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Zong Li <zong.li@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20260918081313.659655-2-zong.li@sifive.com
Signed-off-by: Anup Patel <anup@brainfault.org>
Add BIT_ULL and GENMASK_ULL for dealing with 64-bits data on
32-bits CPU, then we don't need to separate the operation to
low part and high part. For instance, the MMIO register is
64 bits wide.
Signed-off-by: Zong Li <zong.li@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
reg-offset property is used for offset to apply to the mapbase
from the start of the registers in 8250 UART. In Linux kernel,
it has been handled in 8250 UART driver.
dt-bindings:
<linux>/Documentation/devicetree/bindings/serial/8250.yaml
Signed-off-by: Zong Li <zong.li@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
The machine-level MSIP bits are written by accesses to memory-mapped
control registers. Only use CSR instruction for SSIP and USIP.
There is no effect that using CSR instruction to write MSIP when testing
on unleashed board and QEMU.
Signed-off-by: Zong Li <zong.li@sifive.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
Zong Li