[PATCH v2] docs: Correct FW_JUMP_FDT_ADDR calculation example

[Andrew Jones]

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.

>  
>  *FW_JUMP* Example
> -- 
> 2.39.2
>

Anyway,

Reviewed-by: Andrew Jones <ajones at ventanamicro.com>

Thanks,
drew