[PATCH v2] docs: Correct FW_JUMP_FDT_ADDR calculation example

[Gabriel L. Somlo]

On Fri, Mar 24, 2023 at 09:35:31AM +0100, Andrew Jones wrote:
> On Thu, Mar 23, 2023 at 08:42:16PM -0400, Gabriel Somlo wrote:
> > When using `PLATFORM=generic` defaults, the kernel is loaded at
> > `FW_JUMP_ADDR`, and the FDT is loaded at `FW_JUMP_FDT_ADDR.
> > 
> > Therefore, the maximum kernel size before `FW_JUMP_FDT_ADDR` must
> > be increased is `$(( FW_JUMP_FDT_ADDR - FW_JUMP_ADDR ))`.
> > 
> > The example calculation assumes `rv64`, and is wrong to boot
> > (off by 0x200000). Fix it and update it for the general case.
> > 
> > Signed-off-by: Gabriel Somlo <gsomlo at gmail.com>
> > ---
> >  docs/firmware/fw_jump.md | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/docs/firmware/fw_jump.md b/docs/firmware/fw_jump.md
> > index 956897e..03ddf96 100644
> > --- a/docs/firmware/fw_jump.md
> > +++ b/docs/firmware/fw_jump.md
> > @@ -48,13 +48,13 @@ follows:
> >    ```
> >    ${CROSS_COMPILE}objdump -h $KERNEL_ELF | sort -k 5,5 | awk -n '/^ +[0-9]+ /\
> >    {addr="0x"$3; size="0x"$5; printf "0x""%x\n",addr+size}' \
> > -  | (( `tail -1` > 0x2200000 )) && echo fdt overlaps kernel,\
> > -  increase FW_JUMP_FDT_ADDR
> > +  | (( `tail -1` > (FW_JUMP_FDT_ADDR - FW_JUMP_ADDR) )) && \
> > +  echo fdt overlaps kernel, increase FW_JUMP_FDT_ADDR
> >  
> >    ${LLVM}objdump -h --show-lma $KERNEL_ELF | sort -k 5,5 | \
> >    awk -n '/^ +[0-9]+ / {addr="0x"$3; size="0x"$5; printf "0x""%x\n",addr+size}'\
> > -  | (( `tail -1` > 0x2200000 )) && echo fdt overlaps kernel,\
> > -  increase FW_JUMP_FDT_ADDR
> > +  | (( `tail -1` > (FW_JUMP_FDT_ADDR - FW_JUMP_ADDR) )) && \
> > +  echo fdt overlaps kernel, increase FW_JUMP_FDT_ADDR
> >    ```
> 
> nit: We can put a bit of lipstick on this pig by rewriting as
> 
>   ${CROSS_COMPILE}objdump -h $KERNEL_ELF | sort -k 5,5 | awk -n '
>   /^ +[0-9]+ / {addr="0x"$3; size="0x"$5; printf "0x""%x\n",addr+size}' |
>   (( `tail -1` > (FW_JUMP_FDT_ADDR - FW_JUMP_ADDR) )) &&
>   echo fdt overlaps kernel, increase FW_JUMP_FDT_ADDR
> 
>   ${LLVM}objdump -h --show-lma $KERNEL_ELF | sort -k 5,5 | awk -n '
>   /^ +[0-9]+ / {addr="0x"$3; size="0x"$5; printf "0x""%x\n",addr+size}' |
>   (( `tail -1` > (FW_JUMP_FDT_ADDR - FW_JUMP_ADDR) )) &&
>   echo fdt overlaps kernel, increase FW_JUMP_FDT_ADDR
> 
> which drops the unnecessary '\'s and makes the gcc and llvm versions more
> consistent.

Sounds good to me -- you wanna just do that directly while applying,
or should I send a v3? :)
 
> >  
> >  *FW_JUMP* Example
> > -- 
> > 2.39.2
> >
> 
> Anyway,
> 
> Reviewed-by: Andrew Jones <ajones at ventanamicro.com>

Thanks,
--Gabriel