[v1 PATCH 1/1] riscv: Add boot hartid to Device tree

[Atish Patra]

On Tue, Mar 3, 2020 at 11:59 PM Rick Chen <rickchen36 at gmail.com> wrote:
>
> Hi Atish
>
> > From: U-Boot [mailto:u-boot-bounces at lists.denx.de] On Behalf Of Atish Patra
> > Sent: Friday, February 28, 2020 5:01 AM
> > To: u-boot at lists.denx.de
> > Cc: Atish Patra; Alexander Graf; Anup Patel; Bin Meng; Joe Hershberger; Loic Pallardy; Lukas Auer; Marek Behún; Marek Vasut; Patrick Delaunay; Peng Fan; Philippe Reynes; Simon Glass; Simon Goldschmidt; Stefano Babic; Thierry Reding; trini at konsulko.com; Heinrich Schuchardt; Ard Biesheuvel; leif at nuviainc.com; abner.chang at hpe.com; daniel.schaefer at hpe.com
> > Subject: [v1 PATCH 1/1] riscv: Add boot hartid to Device tree
> >
> > 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>
> > ---
> >  arch/riscv/lib/bootm.c | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> >
> > diff --git a/arch/riscv/lib/bootm.c b/arch/riscv/lib/bootm.c index fad16901c5f2..dd359a45c2e1 100644
> > --- a/arch/riscv/lib/bootm.c
> > +++ b/arch/riscv/lib/bootm.c
> > @@ -28,6 +28,19 @@ __weak void board_quiesce_devices(void)
> >
> >  int arch_fixup_fdt(void *blob)
> >  {
> > +       u32 size;
> > +       int chosen_offset, err;
> > +
> > +       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 -1;
> > +       }
> > +       chosen_offset = fdt_path_offset(blob, "/chosen");
> > +       fdt_setprop_u32(blob, chosen_offset, "boot-hartid",
> > +                          gd->arch.boot_hart);
>
> Is it also OK for RV64 ?
>

Yes. I have tested it. To make it compatible for both 32 bit & 64 bit,
I have chosen a 32bit property
which allows the max hartid to be 2^32-1 which should be sufficient.

> Other than that,
> Reviewed-by: Rick Chen <rick at andestech.com>
>
> > +
> >         return 0;
> >  }
> >
> > --
> > 2.24.0
> >



-- 
Regards,
Atish