[PATCH 1/1] board: sifive: unmatched: move kernel load address to 0x80200000

[Yong-Xuan Wang]

Hi Tom,

0x80200000 comes from the result of the relocated_addr in booti_setup()
on HiFive Unmatched board. If we load the Kernel Image to this address,
it will not be moved. Currently one of the first two 8-byte of RISC-V
Kernel Image is j _start_kernel instruction, so it's OK to execute the
header of the Image.

Regards,
Yong-Xuan


On Sat, Oct 28, 2023 at 12:43 AM Tom Rini <trini at konsulko.com> wrote:
>
> On Thu, Oct 26, 2023 at 03:22:52AM +0000, Yong-Xuan Wang wrote:
>
> > U-boot initially loads the kernel image to the kernel_addr_r, and
> > subsequently relocates it to memory address 0x80200000. Setting
> > kernel_addr_r to 0x80200000 can eliminate one copy operation.
> >
> > Signed-off-by: Yong-Xuan Wang <yongxuan.wang at sifive.com>
> > ---
> >  include/configs/sifive-unmatched.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/configs/sifive-unmatched.h b/include/configs/sifive-unmatched.h
> > index 74150b7d4b..de8bfc1123 100644
> > --- a/include/configs/sifive-unmatched.h
> > +++ b/include/configs/sifive-unmatched.h
> > @@ -36,7 +36,7 @@
> >       "name=system,size=-,bootable,type=${type_guid_gpt_system};"
> >
> >  #define CFG_EXTRA_ENV_SETTINGS \
> > -     "kernel_addr_r=0x84000000\0" \
> > +     "kernel_addr_r=0x80200000\0" \
> >       "kernel_comp_addr_r=0x88000000\0" \
> >       "kernel_comp_size=0x4000000\0" \
> >       "fdt_addr_r=0x8c000000\0" \
>
> This is I believe subtly wrong. If you want an execute in place kernel
> image (and are using FIT images), this can be made to work. But if you
> load your (Linux Kernel) Image to this address, the header will be at
> 0x80200000 and not the payload so you still end up moving it. Are you
> sure this is (a) not still moving it and (b) it's OK to be executing the
> header of the image like it's code (or is there some catch in the header
> to lead to a jump over it, in that case) ?
>
> --
> Tom