[U-Boot] [PATCH 12/13] armv7: support rk3066 early back to bootrom in start.S

[Simon Glass]

Hi Pawel,

On 6 June 2017 at 12:53, Paweł Jarosz <paweljarosz3691 at gmail.com> wrote:
> Rockchip bootrom first reads 1KB data from nand at offset 0x10080C00 and
> executes it. Then waits for back to bootrom and loads another 32KB to sram
> which also executes. Sdram initialisation code needs to be in one of these two
> steps. Then bootloader loads another ~200KB of data at offset 0x60000000
> and jumps to it.
>
> 32KB of data is a little low for tpl + spl part and ~200KB data is to low for
> u-boot part(for example to boot from mmc you need to disable usb support.
>
> My solution to size problem is to move sdram initialisation code to tpl stage,
> move spl part to third stage(reading 200KB data) and add support for loading
> u-boot by spl from ext2/4, fat partitions.
>
> But moving sdram initialisation code to tpl increases size of tpl above 1KB
> (first boot stage). Solution to this is to add code which will be below 1KB
> offset in tpl binary and do back to bootrom at very beginning of the tpl
> execution.

So do you mean that TPL starts and then loads more of itself? Why not
put SDRAM init in SPL? You say above that 32KB is 'too low', but It's
not clear why.

>
> Adding this few lines of code here meets these conditions.
>
> Signed-off-by: Paweł Jarosz <paweljarosz3691 at gmail.com>
> ---
>  arch/arm/cpu/armv7/start.S | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/arch/arm/cpu/armv7/start.S b/arch/arm/cpu/armv7/start.S
> index f06fd28..73e03d9 100644
> --- a/arch/arm/cpu/armv7/start.S
> +++ b/arch/arm/cpu/armv7/start.S
> @@ -36,6 +36,19 @@
>  #endif
>
>  reset:
> +
> +#if defined(CONFIG_ROCKCHIP_RK3066) && defined(CONFIG_TPL_BUILD)
> +       ldr     r3, =0x10080900
> +       ldr     r0, [r3]
> +       cmp     r0, #1
> +       movne   r0, #1
> +       strne   r0, [r3]
> +       beq     out_of_bootrom
> +       bx      lr
> +out_of_bootrom:
> +       mov     r0, #0
> +       str     r0, [r3]
> +#endif
>         /* Allow the board to save important registers */
>         b       save_boot_params
>  save_boot_params_ret:
> --
> 2.7.4
>

Regards,
Simon