On 4/6/20 10:44 PM, Atish Patra wrote:
> Linux booting protocol mandates that register "a0" contains the hartid.
> However, U-boot can not pass the hartid via a0 during via standard UEFI
> protocol. DT nodes are commonly used to pass such information to the OS.
>
> Add a DT node under chosen node to indicate the boot hartid. EFI stub
> in Linux kernel will parse this node and pass it to the real kernel
> in "a0" before jumping to it.
>
> Signed-off-by: Atish Patra <[email protected]>
> Reviewed-by: Rick Chen <[email protected]>
> ---
> arch/riscv/lib/bootm.c | 22 ++++++++++++++++++++++
> 1 file changed, 22 insertions(+)
>
> diff --git a/arch/riscv/lib/bootm.c b/arch/riscv/lib/bootm.c
> index fad16901c5f2..87cadad5016d 100644
> --- a/arch/riscv/lib/bootm.c
> +++ b/arch/riscv/lib/bootm.c
> @@ -28,6 +28,28 @@ __weak void board_quiesce_devices(void)
>
> int arch_fixup_fdt(void *blob)
> {
> +#ifdef CONFIG_EFI_LOADER
> + int err;
> + u32 size;
> + int chosen_offset;
> +
> + size = fdt_totalsize(blob);
> + err = fdt_open_into(blob, blob, size + 32);
> + if (err < 0) {
> + printf("Device Tree can't be expanded to accommodate new node");
> + return err;
> + }
> + chosen_offset = fdt_path_offset(blob, "/chosen");
> + if (chosen_offset < 0) {
> + err = fdt_add_subnode(blob, 0, "chosen");
> + if (err < 0) {
> + printf("chosen node can not be added\n");
> + return err;
> + }
> + }
> + /* Overwrite the boot-hartid as U-Boot is the last stage BL */
> + fdt_setprop_u32(blob, chosen_offset, "boot-hartid", gd->arch.boot_hart);
> +#endif
> return 0;
> }
>
>
I have tested this on qemu-riscv64_defconfig by comparing the device
tree before and after running helloworld.efi:
=> fdt addr $fdtcontroladdr
=> fdt print /chosen
chosen {
bootargs = "";
stdout-path = "/uart@10000000";
};
...
=> dhcp $kernel_addr_r helloworld.efi
=> bootefi $kernel_addr_r
...
=> fdt addr 0x87F00000
=> fdt print /chosen
chosen {
riscv,kernel-end = <0x00000000 0x00000000>;
riscv,kernel-start = <0x00000000 0x00000000>;
boot-hartid = <0x00000000>;
bootargs = "";
stdout-path = "/uart@10000000";
};
The entry for boot-hardid seems to be ok.
But the riscv,kernel-end and riscv,kernel-start values are just some
dummy values introduced in:
board/emulation/qemu-riscv/qemu-riscv.c:84
commit 897206c5cc5c ("riscv: qemu: clear kernel-start/-end in device
tree as workaround for BBL)"
@Lukas:
Why are these values set to zero and not deleted (using fdt_delprop())
from the device tree? I cannot see that we need them when booting via UEFI.
Tested-by: Heinrich Schuchardt <[email protected]>
