[PATCH v5 1/6] riscv: Add boot hartid to Device tree

[Bin Meng]

Hi Heinrich,

On Tue, Apr 14, 2020 at 7:05 AM Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>
> 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 <atish.patra at wdc.com>
> > Reviewed-by: Rick Chen <rick at andestech.com>
> > ---
> >  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 at 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 at 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.
>

This should be removed as BBL is legacy and we only support working
with OpenSBI.

> Tested-by: Heinrich Schuchardt <xypron.glpk at gmx.de>

Regards,
Bin